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MAX1717EEG+-MAX1717EEG-T
Dynamically Adjustable, Synchronous Step-Down Controller for Notebook CPUs
General DescriptionThe MAX1717 step-down controller is intended for core
CPU DC-DC converters in notebook computers. It fea-
tures a dynamically adjustable output, ultra-fast tran-
sient response, high DC accuracy, and high efficiency
needed for leading-edge CPU core power supplies.
Maxim’s proprietary Quick-PWM™ quick-response,
constant-on-time PWM control scheme handles wide
input/output voltage ratios with ease and provides
100ns “instant-on” response to load transients while
maintaining a relatively constant switching frequency.
The output voltage can be dynamically adjusted
through the 5-bit digital-to-analog converter (DAC)
inputs over a 0.925V to 2V range. A unique feature of
the MAX1717 is an internal multiplexer (mux) that
accepts two 5-bit DAC settings with only five digital
input pins. Output voltage transitions are accomplished
with a proprietary precision slew-rate control†that mini-
mizes surge currents to and from the battery while
guaranteeing “just-in-time” arrival at the new DAC setting.
High DC precision is enhanced by a two-wire remote-
sensing scheme that compensates for voltage drops in
the ground bus and output voltage rail. Alternatively,
the remote-sensing inputs can be used together with
the MAX1717’s high DC accuracy to implement a volt-
age-positioned circuit that modifies the load-transient
response to reduce output capacitor requirements and
full-load power dissipation.
Single-stage buck conversion allows these devices to
directly step down high-voltage batteries for the highest
possible efficiency. Alternatively, two-stage conversion
(stepping down the +5V system supply instead of the
battery) at a higher switching frequency allows the mini-
mum possible physical size.
The MAX1717 is available in a 24-pin QSOP package.
ApplicationsNotebook Computers with SpeedStep™ or
Other Dynamically Adjustable Processors
2-Cell to 4-Cell Li+ Battery to CPU Core Supply
Converters
5V to CPU Core Supply Converters
FeaturesQuick-PWM Architecture ±1% VOUTAccuracy Over Line and Load5-Bit On-Board DAC with Input MuxPrecision-Adjustable VOUTSlew Control 0.925V to 2V Output Adjust RangeSupports Voltage-Positioned Applications2V to 28V Battery Input Range Requires a Separate +5V Bias Supply200/300/550/1000kHz Switching FrequencyOver/Undervoltage ProtectionDrives Large Synchronous-Rectifier FETs700µA (typ) ICCSupply Current2µA (typ) Shutdown Supply Current2V ±1% Reference Output VGATE Transition-Complete Indicator Small 24-Pin QSOP Package
MAX1717
Dynamically Adjustable, Synchronous
Step-Down Controller for Notebook CPUs19-1636; Rev 3; 8/05
Ordering Information
Pin Configuration appears at end of data sheet.†P.
Quick-PWM is a trademark of Maxim Integrated Products.
SpeedStep is a trademark of Intel Corp.TIME
VGATE
BST
+5V INPUT
ILIM
GNDS
FBS
REF
TON
GND
MAX1717
VCCVDD
SKP/SDN
OUTPUT
0.925V TO 2V
DAC
INPUTS
BATTERY
2.5V TO 28V
A/B
Minimal Operating Circuit
EVALUATION KIT
AVAILABLE
PARTTEMP RANGEPIN-PACKAGEMAX1717EEG-40°C to +85°C24 QSOP
MAX1717EEG+-40°C to +85°C24 QSOP
+ Denotes lead-free package.
MAX1717
Dynamically Adjustable, Synchronous
Step-Down Controller for Notebook CPUs
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS(Circuit of Figure 1, V+ = +15V, VCC= VDD= SKP/SDN= +5V, VOUT= 1.6V, TA
= 0°C to +85°C, unless otherwise noted.)Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
V+ to GND..............................................................-0.3V to +30V
VCC, VDDto GND.....................................................-0.3V to +6V
D0–D4, A/B,VGATE, to GND ..................................-0.3V to +6V
SKP/SDNto GND...................................................-0.3V to +16V
ILIM, FB, FBS, CC, REF, GNDS,TON,
TIME to GND..........................................-0.3V to (VCC+ 0.3V)
DL to GND..................................................-0.3V to (VDD+ 0.3V)
BST to GND............................................................-0.3V to +36V
DH to LX.....................................................-0.3V to (BST + 0.3V)
LX to BST..................................................................-6V to +0.3V
REF Short Circuit to GND...........................................Continuous
Continuous Power Dissipation
24-Pin QSOP (derate 9.5mW/°C above +70°C)..........762mW
Operating Temperature Range ..........................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature.........................................-65°C to +150°C
Lead Temperature (soldering, 10s).................................+300°C
VCC= 4.5V to 5.5V, no REF load
SKP/SDN= 0, VCC= VDD= 0 or 5V
SKP/SDN= 0
SKP/SDN= 0
VCC, VDD
Measured at VDD, FB forced above the regulation point
Battery voltage, V+
Measured at VCC, FB forced above the regulation point
TON = GND (1000kHz)
TON = VCC, open, or REF (200kHz, 300kHz, or 550kHz)
38kHz nominal, RTIME= 470kΩ
380kHz nominal, RTIME= 47kΩ
150kHz nominal, RTIME= 120kΩ
TON = VCC(200kHz)
FB to FBS or GNDS to GND = 0 to 25mV
VCC= 4.5V to 5.5V, VBATT= 4.5V to 28V
V+ = 24V, FB = 2V
V+ = 5V, FB = 2V, TON = GND (1000kHz)
CONDITIONS1.9822.02
DAC codes from 1.3V to 2V
Reference Voltage<15
Shutdown Battery Supply
Current (V+)<151
Shutdown Supply Current (VDD)25Shutdown Supply Current (VCC)2540
DAC codes from 0.925V to 1.275V
Quiescent Battery Supply
Current (V+)<15
Quiescent Supply Current (VDD)7001200
TON = open (300kHz)
Quiescent Supply Current (VCC)300375
TON = REF (550kHz)
Minimum Off-Time (Note 2)400500Minimum Off-Time (Note 2)
135155173ns
On-Time (Note 2)
4.55.5V228Input Voltage Range
-12+12-12+12+8
TIME Frequency Accuracy-11GNDS Input Bias Current3Remote Sense Voltage Error5Line Regulation Error115180265FB Input Resistance
UNITSMINTYPMAXPARAMETER-0.20.2FBS Input Bias Current
V+ = 4.5V to 28V,
includes load
regulation error
DC Output Voltage Accuracy
(Note 1)
PWM CONTROLLER
BIAS AND REFERENCE
MAX1717
Dynamically Adjustable, Synchronous
Step-Down Controller for Notebook CPUs
ELECTRICAL CHARACTERISTICS (continued)(Circuit of Figure 1, V+ = +15V, VCC= VDD= SKP/SDN= +5V, VOUT= 1.6V, TA
= 0°C to +85°C, unless otherwise noted.)Current-Limit Threshold
(Zero Crossing)4mVGND - LX
DH Gate Driver On-Resistance1.03.5ΩBST - LX forced to 5V
Current-Limit Default
Switchover Threshold3VCC-1VCC-0.4V= 0°C to +85°C85115= +25°C to +85°C
ILIM = REF (2V)
ILIM = 0.5V
PARAMETERMINTYPMAXUNITSOutput Undervoltage Fault
Blanking Time256clks
Output Undervoltage Fault
Propagation Delay10µs
Output Undervoltage Fault
Protection Threshold657075%
Overvoltage Fault Propagation
Delay10µs
Current-Limit Threshold
(Positive, Default)100110
Current-Limit Threshold
(Positive, Adjustable)5065mV165200230
REF Sink Current
Reference Load Regulation0.01VµA
Overvoltage Trip Threshold2.202.252.30V
Current-Limit Threshold
(Negative)-140-110-80mV
Thermal Shutdown Threshold150°C
VCCUndervoltage Lockout
Threshold4.14.4V
1.03.5DL Gate Driver On-Resistance 0.41.0Ω
DH Gate-Driver Source/Sink
Current 1.3A
DL Gate-Driver Sink Current4A
CONDITIONSLX - GND, ILIM = VCC
From SKP/SDNsignal going high, clock speed set by RTIME
Hysteresis = 10°C
FB forced 2% below trip threshold
With respect to unloaded output voltage
FB forced 2% above trip threshold
GND - LX, ILIM = VCC
Rising edge, hysteresis = 20mV, PWM disabled below
this level
GND - LX
DL, high state (pullup)
DL, low state (pulldown)
DH forced to 2.5V, BST - LX forced to 5V
IREF= 0 to 50µA
DL forced to 2.5V
REF in regulation
Measured at FB
VGATE Lower Trip Threshold-8-6.5-5%Measured at FB with respect to unloaded output voltage,
rising edge, hysteresis = 1%
VGATE Upper Trip Threshold+10+12+14%Measured at FB with respect to unloaded output voltage,
rising edge, hysteresis = 1%
VGATE Propagation Delay10µsFB forced 2% outside VGATE trip threshold
VGATE Output Low Voltage0.4VISINK= 1mA
VGATE Transition Delay1clkAfter X = Y, clock speed set by RTIME
VGATE Leakage Current1µAHigh state, forced to 5.5V
GATE DRIVERS
FAULT PROTECTION
MAX1717
Dynamically Adjustable, Synchronous
Step-Down Controller for Notebook CPUs
ELECTRICAL CHARACTERISTICS (continued)(Circuit of Figure 1, V+ = +15V, VCC= VDD= SKP/SDN= +5V, VOUT= 1.6V, TA
= 0°C to +85°C, unless otherwise noted.)
ELECTRICAL CHARACTERISTICS(Circuit of Figure 1, V+ = +15V, VCC= VDD= SKP/SDN= +5V, VOUT= 1.6V, TA
= -40°C to +85°C, unless otherwise noted.) (Note 3)
PARAMETERMINTYPMAXUNITSOn-Time (Note 2)375475ns
On-Time (Note 2)
Minimum Off-Time (Note 2)500ns
Minimum Off-Time (Note 2)
TON = REF (550kHz)
375ns
TON = open (300kHz)
CONDITIONSV+ = 5V, FB = 2V, TON = GND (1000kHz)
V+ = 24V, FB = 2V
TON = VCC(200kHz)
TON = VCC, open, or REF (200kHz, 300kHz, or 550kHz)
TON = GND (1000kHz)
TIME Frequency Accuracy+8
-12+12%
-12+12
150kHz nominal, RTIME= 120kΩ
380kHz nominal, RTIME= 47kΩ
38kHz nominal, RTIME= 470kΩ
DC Output Voltage Accuracy
(Note 1)
DAC codes from 1.3V to 2VV+ = 4.5V to 28V,
includes load
regulation errorDAC codes from 0.925V to 1.275V
PARAMETERCONDITIONSMINTYPMAXUNITS1.3DL forced to 2.5VDL Gate-Driver Source Current
D0–D4 Pullup/PulldownEntering B modePull up
Pull downkΩ-111
D0–D4, A/B= 5V
A/BLogic Input Current
TON Input Levels
For TON = VCC(200kHz operation)
For TON = open (300kHz operation)
For TON = REF (550kHz operation)
For TON = GND (1000kHz operation)
VCC- 0.4
0.5-33SKP/SDN, TON forced to GND or VCCSKP/SDNand TON Input Current
SKP/SDNInput Levels
SKP/SDN= logic high (SKIP mode)
SKP/SDN= open (PWM mode)
SKP/SDN= logic low (shutdown mode)
To enable no-fault mode15
2.8695D0–D4, 0 to 0.4V or 2.6V to 5.5V applied through resistor,
A/B= GND
DAC B-Mode Programming
Resistor, High
1.05D0–D4, 0 to 0.4V or 2.6V to 5.5V applied through resistor,
A/B= GND
DAC B-Mode Programming
Resistor, Low
0.8D0–D4, A/BLogic Input Low Voltage
2.4D0–D4, A/BLogic Input High VoltageDH risingns35DL risingDead Time
LOGIC AND I/O
MAX1717
Dynamically Adjustable, Synchronous
Step-Down Controller for Notebook CPUs
ELECTRICAL CHARACTERISTICS (continued)(Circuit of Figure 1, V+ = +15V, VCC= VDD= SKP/SDN= +5V, VOUT=1.6V, TA
= -40°C to +85°C, unless otherwise noted.) (Note 3)VGATE Lower Trip Threshold-8.4-4.6%
VGATE Upper Trip Threshold+10+15%
Measured at FB with respect to unloaded output voltage,
falling edge, hysteresis = 1%
Measured at FB with respect to unloaded output voltage,
rising edge, hysteresis = 1%
ILIM = REF (2V)
ILIM = 0.5V
DAC B-Mode Programming
Resistor, Low1kΩ
DAC B-Mode Programming
Resistor, High 100kΩ
Output Undervoltage Protection
Threshold 6575%
Current-Limit Threshold
(Positive, Default)80115mV
Current-Limit Threshold
(Positive, Adjustable)65mV160240
Overvoltage Trip Threshold2.202.30V
Current-Limit Threshold
(Negative)-140-80mV
VCCUndervoltage Lockout
Threshold
D0–D4, 0 to 0.4V or 2.6V to 5.5V applied through resistor,
A/B= GND
4.14.4V
DH Gate Driver On-Resistance
D0–D4, 0 to 0.4V or 2.6V to 5.5V applied through resistor,
A/B= GND
3.5Ω
DL Gate Driver On-Resistance 3.5Ω
1.0Ω
Logic Input High Voltage2.4V
Logic Input Low Voltage0.8V
LX - GND, ILIM = VCC
With respect to unloaded output voltage
GND - LX, ILIM = VCC
Rising edge, hysteresis = 20mV, PWM disabled below this
level
BST - LX forced to 5V
GND - LX
DL, high state (pullup)
DL, low state (pulldown)
Measured at FB
D0–D4, A/B
D0–D4, A/B
PARAMETERMINTYPMAXUNITSQuiescent Supply Current (VCC)1200µA
Shutdown Battery Supply
Current (V+)5µA
Reference Voltage1.982.02V
CONDITIONSMeasured at VCC, FB forced above the regulation point
SKP/SDN= 0, VCC= VDD= 0 or 5V
VCC= 4.5V to 5.5V, no REF load
Note 1:Output voltage accuracy specifications apply to DAC voltages from 0.925V to 2V. Includes load-regulation error.
Note 2:On-Time specifications are measured from 50% to 50% at the DH pin, with LX forced to 0, BST forced to 5V, and a 500pF
capacitor from DH to LX to simulate external MOSFET gate capacitance. Actual in-circuit times may be different due to
MOSFET switching speeds.
Note 3:Specifications to -40°C are guaranteed by design and not production tested.
Shutdown Supply Current (VCC)5µA
Shutdown Supply Current (VDD)5µA
SKP/SDN= 0
SKP/SDN= 0
Quiescent Battery Supply
Current (V+)40µA
Quiescent Supply Current (VDD)5µAMeasured at VDD, FB forced above the regulation point
MAX1717
Dynamically Adjustable, Synchronous
Step-Down Controller for Notebook CPUs
Typical Operating Characteristics(Circuit of Figure 1, components of Table 1, V+ = +12V, VDD= VCC= SKP/SDN= +5V, VOUT= 1.6V, TA= +25°C, unless otherwise noted.)
EFFICIENCY vs. LOAD CURRENT
300kHz STANDARD APPLICATION,
CIRCUIT 1
MAX1717 toc01
LOAD CURRENT (A)
EFFICIENCY (%)
SKIP MODE, V+ = 7V
SKIP MODE, V+ = 12V
SKIP MODE,
V+ = 20V
PWM MODE,
V+ = 7V
PWM MODE, V+ = 12V
PWM MODE, V+ = 20V
EFFICIENCY vs. LOAD CURRENT
300kHz VOLTAGE POSITIONED, CIRCUIT 2
MAX1717 toc02
LOAD CURRENT (A)
EFFICIENCY (%)
SKIP MODE, V+ = 7V
SKIP MODE, V+ = 12V
SKIP MODE,
V+ = 20V
PWM MODE,
V+ = 12V
PWM MODE,
V+ = 20V
PWM
MODE,
V+ = 7V
EFFECTIVE EFFICIENCY vs. LOAD CURRENT
300kHz VOLTAGE POSITIONED, CIRCUIT 2
MAX1717 toc03
NONPOSITIONED LOAD CURRENT (A)
EFFECTIVE EFFICIENCY (%)
SKIP MODE, V+ = 7V
SKIP MODE, V+ = 12V
SKIP MODE,
V+ = 20V
PWM MODE,
V+ = 7V
PWM MODE, V+ = 12V
PWM MODE, V+ = 20V
EFFICIENCY vs. LOAD CURRENT
550kHz VOLTAGE POSITIONED, CIRCUIT 3
MAX1717 toc04
LOAD CURRENT (A)
EFFICIENCY (%)
SKIP MODE, V+ = 7V
SKIP MODE, V+ = 12V
SKIP MODE,
V+ = 20V
PWM MODE,
V+ = 12V
PWM MODE,
V+ = 7V
PWM MODE, V+ = 20V50
EFFECTIVE EFFICIENCY vs. LOAD CURRENT
550kHz VOLTAGE POSITIONED, CIRCUIT 3
MAX1717 toc05
NONPOSITIONED LOAD CURRENT (A)
EFFECTIVE EFFICIENCY (%)
SKIP MODE, V+ = 7V
SKIP MODE, V+ = 12V
SKIP MODE,
V+ = 20V
PWM MODE,
V+ = 12V
PWM MODE,
V+ = 7V
PWM MODE, V+ = 20V50
EFFICIENCY vs. LOAD CURRENT
1000kHz, +5V, CIRCUIT 4
MAX1717 toc06
LOAD CURRENT (A)
EFFICIENCY (%)
SKIP MODE
PWM MODE
EFFECTIVE EFFICIENCY vs. LOAD CURRENT
1000kHz, +5V, CIRCUIT 4
MAX1717 toc07
NONPOSITIONED LOAD CURRENT (A)
EFFECTIVE EFFICIENCY (%)
SKIP MODE
PWM MODE
EFFICIENCY vs. LOAD CURRENT
1000kHz VOLTAGE POSITIONED,
CIRCUIT 5
MAX1717 toc08
LOAD CURRENT (A)
EFFICIENCY (%)
SKIP MODE, V+ = 7V
SKIP MODE, V+ = 12V
SKIP MODE,
V+ = 20V
PWM MODE,
V+ = 20V
PWM MODE,
V+ = 12V
PWM MODE,
V+ = 7V
EFFECTIVE EFFICIENCY vs. LOAD CURRENT
1000kHz VOLTAGE POSITIONED,
CIRCUIT 5
MAX1717 toc09
NONPOSITIONED LOAD CURRENT (A)
EFFECTIVE EFFICIENCY (%)
SKIP MODE, V+ = 7V
SKIP MODE, V+ = 12V
SKIP MODE,
V+ = 20V
PWM MODE,
V+ = 20V
PWM MODE,
V+ = 12V
PWM MODE,
V+ = 7V
MAX1717
Dynamically Adjustable, Synchronous
Step-Down Controller for Notebook CPUsFREQUENCY vs. LOAD CURRENT
MAX1717 toc10
LOAD CURRENT (A)
FREQUENCY (kHz)
300kHz VOLTAGE POSITIONED, CIRCUIT 2
SKIP MODE
PWM MODE
FREQUENCY vs. LOAD CURRENT
MAX1717 toc11
LOAD CURRENT (A)
FREQUENCY (kHz)
1000kHz VOLTAGE POSITIONED, CIRCUIT 5
SKIP MODE
PWM MODE
FREQUENCY vs. INPUT VOLTAGE
MAX1717 toc12
INPUT VOLTAGE (V)
FREQUENCY (kHz)
300kHz VOLTAGE POSITIONED, CIRCUIT 2
IOUT = 12A
IOUT = 0.3A
FREQUENCY vs. INPUT VOLTAGE
MAX1717 toc13
INPUT VOLTAGE (V)
FREQUENCY (kHz)
1000kHz VOLTAGE POSITIONED, CIRCUIT 5
IOUT = 12A
IOUT = 0.3A
FREQUENCY vs. TEMPERATURE
MAX1717 toc14
TEMPERATURE (°C)
FREQUENCY (kHz)
300kHz VOLTAGE POSITIONED, CIRCUIT 2
OUTPUT CURRENT AT CURRENT LIMIT
vs. TEMPERATURE
MAX1717 toc15
TEMPERATURE (°C)
CURRENT (A)
300kHz VOLTAGE POSITIONED, CIRCUIT 2
CONTINUOUS-TO-DISCONTINUOUS
INDUCTOR CURRENT POINT
MAX1717 toc16
INPUT VOLTAGE (V)
LOAD CURRENT (A)
300kHz VOLTAGE POSITIONED, CIRCUIT 2
INDUCTOR CURRENT PEAKS AND
VALLEYS vs. INPUT VOLTAGE
MAX1717 toc17
INPUT VOLTAGE (V)
INDUCTOR CURRENT (A)
AT CURRENT-LIMIT POINT
300kHz VOLTAGE POSITIONED, CIRCUIT 2
IPEAK
IVALLEY
NO-LOAD SUPPLY CURRENT
vs. INPUT VOLTAGE
MAX1717 toc18
INPUT VOLTAGE (V)
SUPPLY CURRENT (
300kHz VOLTAGE POSITIONED, CIRCUIT 2,
SKIP MODE
ICC + IDD
Typical Operating Characteristics (continued)(Circuit of Figure 1, components of Table 1, V+ = +12V, VDD= VCC= SKP/SDN= +5V, VOUT= 1.6V, TA= +25°C, unless otherwise noted.)
MAX1717
Dynamically Adjustable, Synchronous
Step-Down Controller for Notebook CPUsNO-LOAD SUPPLY CURRENT
vs. INPUT VOLTAGE
MAX1717 toc19
INPUT VOLTAGE (V)
SUPPLY CURRENT (
1000kHz VOLTAGE POSITIONED, CIRCUIT 5,
SKIP MODE
ICC + IDD
NO-LOAD SUPPLY CURRENT
vs. INPUT VOLTAGE
MAX1717 toc20
INPUT VOLTAGE (V)
SUPPLY CURRENT (mA)
300kHz VOLTAGE POSITIONED,
CIRCUIT 2, PWM MODE
ICC + IDD
NO-LOAD SUPPLY CURRENT
vs. INPUT VOLTAGE
MAX1717 toc21
INPUT VOLTAGE (V)
SUPPLY CURRENT (mA)
550kHz VOLTAGE POSITIONED,
CIRCUIT 3, PWM MODE
ICC + IDD
NO-LOAD SUPPLY CURRENT
vs. INPUT VOLTAGE
MAX1717 toc22
INPUT VOLTAGE (V)
SUPPLY CURRENT (mA)
1000kHz VOLTAGE POSITIONED,
CIRCUIT 5, PWM MODE
ICC + IDD
10μs/div
LOAD-TRANSIENT RESPONSEMAX1717 toc23
A = VOUT, 50mV/div, AC-COUPLED
B = INDUCTOR CURRENT, 10A/div
300kHz STANDARD APPLICATION, CIRCUIT 1,
PWM MODE
10μs/div
LOAD-TRANSIENT RESPONSEMAX1717 toc24
A = VOUT, 50mV/div, AC-COUPLED
B = INDUCTOR CURRENT, 10A/div
300kHz VOLTAGE POSITIONED,
CIRCUIT 2, PWM MODE
5μs/div
LOAD-TRANSIENT RESPONSEMAX1717 toc25
A = VOUT, 50mV/div, AC-COUPLED
B = INDUCTOR CURRENT, 10A/div
550kHz VOLTAGE POSITIONED, CIRCUIT 3,
PWM MODE
4μs/div
LOAD-TRANSIENT RESPONSEMAX1717 toc26
A = VOUT, 50mV/div, AC-COUPLED
B = INDUCTOR CURRENT, 10A/div
1000kHz +5V, CIRCUIT 4, PWM MODE
4μs/div
LOAD-TRANSIENT RESPONSEMAX1717 toc27
A = VOUT, 50mV/div, AC-COUPLED
B = INDUCTOR CURRENT, 10A/div
1000kHz VOLTAGE POSITIONED, CIRCUIT 5,
PWM MODE
Typical Operating Characteristics (continued)(Circuit of Figure 1, components of Table 1, V+ = +12V, VDD= VCC= SKP/SDN= +5V, VOUT= 1.6V, TA= +25°C, unless otherwise noted.)
MAX1717
Dynamically Adjustable, Synchronous
Step-Down Controller for Notebook CPUs100μs/div
STARTUP WAVEFORMMAX1717 toc28
A = VOUT, 1V/div
B = INDUCTOR CURRENT, 10A/div
C = SKP/SDN, 5V/div
300kHz VOLTAGE POSITIONED,
CIRCUIT 2, PWM MODE,
NO LOAD
100μs/div
STARTUP WAVEFORMMAX1717 toc29
A = VOUT, 1V/div
B = INDUCTOR CURRENT, 10A/div
C = SKP/SDN, 5V/div
300kHz VOLTAGE POSITIONED,
CIRCUIT 2, IOUT =12A
50μs/div
DYNAMIC OUTPUT VOLTAGE TRANSITIONMAX1717 toc30
300kHz STANDARD APPLICATION, CIRCUIT 1,
PWM MODE, VOUT = 1.35V TO 1.6V, IOUT = 0.3A,
RTIME = 120kΩ
A = VOUT, 200mV/div, AC-COUPLED
B = INDUCTOR CURRENT, 10A/div
C = VGATE, 5V/div
D = A/B, 5V/div
50μs/div
DYNAMIC OUTPUT VOLTAGE TRANSITIONMAX1717 toc31
300kHz STANDARD APPLICATION, CIRCUIT 1,
PWM MODE, VOUT = 1.35V TO 1.6V,
IOUT = 12A, RTIME = 120kΩ
A = VOUT, 200mV/div, AC-COUPLED
B = INDUCTOR CURRENT, 10A/div
C = VGATE, 5V/div
D = A/B, 5V/div
20μs/div
DYNAMIC OUTPUT VOLTAGE TRANSITIONMAX1717 toc32
A = VOUT, 200mV/div, AC-COUPLED
B = INDUCTOR CURRENT, 10A/div
C = VGATE, 5V/div
D = A/B, 5V/div
1000kHz +5V, CIRCUIT 4,
PWM MODE, VOUT = 1.35V TO 1.6V,
IOUT = 0.3A, RTIME = 51kΩ
40μs/div
OUTPUT OVERLOAD WAVEFORMMAX1717 toc33
A = VOUT, 500mV/div
B = INDUCTOR CURRENT, 10A/div
300kHz VOLTAGE POSITIONED, CIRCUIT 2,
PWM MODE
Typical Operating Characteristics (continued)(Circuit of Figure 1, components of Table 1, V+ = +12V, VDD= VCC= SKP/SDN= +5V, VOUT= 1.6V, TA= +25°C, unless otherwise noted.)
MAX1717
Dynamically Adjustable, Synchronous
Step-Down Controller for Notebook CPUs
Pin Description
Typical Operating Characteristics (continued)(Circuit of Figure 1, components of Table 1, V+ = +12V, VDD= VCC= SKP/SDN= +5V, VOUT= 1.6V, TA= +25°C, unless otherwise noted.)
100μs/div
SHUTDOWN WAVEFORMMAX1717 toc34
300kHz VOLTAGE POSITIONED, CIRCUIT 2,
PWM MODE, NO LOAD
A = VOUT, 1V/div
B = INDUCTOR CURRENT, 10A/div
C = SKP/SDN, 5V/div
100μs/div
SHUTDOWN WAVEFORMMAX1717 toc35
300kHz VOLTAGE POSITIONED, CIRCUIT 2,
PWM MODE, IOUT = 12A
A = VOUT, 1V/div
B = INDUCTOR CURRENT, 10A/div
C = SKP/SDN, 5V/div
Feedback Remote-Sense Input. For nonvoltage-positioned circuits, connect FBS to VOUTdirectly at the
load. FBS internally connects to the integrator that fine tunes the DC output voltage. For voltage-positioned
circuits, connect FBS directly to FB near the IC to disable the FBS remote-sense integrator amplifier. To dis-
able all three integrator amplifiers, connect FBS to VCC.
FBS5
Integrator Capacitor Connection. Connect a 100pF to 1000pF (470pF typ) capacitor from CC to GND to set
the integration time constant. CC can be left open if FBS is tied to VCC.CC6
Analog Supply Voltage Input for PWM Core. Connect VCCto the system supply voltage (4.5V to 5.5V) with a
series 20Ωresistor. Bypass to GND with a 0.22µF (min) capacitor. VCC7
Fast Feedback Input. Connect FB to the junction of the external inductor and output capacitor for nonvolt-
age-positioned circuits (Figure 1). For voltage-positioned circuits, connect FB to the junction of the external
inductor and the positioning resistor (Figure 3).4
Slew-Rate Adjustment Pin. Connect a resistor from TIME to GND to set the internal slew-rate clock. A 470kΩ
to 47kΩresistor sets the clock from 38kHz to 380kHz, fSLEW= 150kHz x120kΩ/ RTIME.TIME3
PINCombined Shutdown and Skip-Mode Control. Drive SKP/SDNto GND for shutdown. Leave SKP/SDNopen for
low-noise forced-PWM mode, or drive to VCCfor normal pulse-skipping operation. Low-noise forced-PWM mode
causes inductor current recirculation at light loads and suppresses pulse-skipping operation. SKP/SDNcan also
be used to disable over/undervoltage protection circuits and clear the fault latch by forcing it to 12V < SKP/SDN
< 15V (with otherwise normal PFM/PWM operation). Do not connect SKP/SDNto > 15V.
SKP/SDN2
Battery Voltage Sense Connection. Connect V+ to input power source. V+ is used only for PWM one-shot
timing. DH on-time is inversely proportional to input voltage over a range of 2V to 28V.V+1
FUNCTIONNAME
MAX1717
Dynamically Adjustable, Synchronous
Step-Down Controller for Notebook CPUs
Pin Description (continued)Boost Flying Capacitor Connection. Connect BST to the external boost diode and capacitor as shown in the
Standard Application Circuit. An optional resistor in series with BST allows the DH pullup current to be
adjusted (Figure 5).
BST22
Inductor Connection. LX is the internal lower supply rail for the DH high-side gate driver. It also connects to
the current-limit comparator and the skip-mode zero-crossing comparator. LX23
High-Side Gate-Driver Output. DH swings LX to BST.DH24
DAC Code Inputs. D0 is the LSB and D4 is the MSB for the internal 5-bit DAC (see Table 4). When A/Bis
high, D0–D4 function as high-input-impedance logic inputs. On the falling edge of A/B(or during power-up
with A/Blow), the series resistance on each input sets its logic state as follows:
(series resistance ≤1kΩ±5%) = logic low
(series resistance ≥100kΩ±5%) = logic high
D4–D017–21
Internal MUX Select Input. When A/Bis high, the DAC code is determined by logic-level voltages on D0–D4.
On the falling edge of A/B(or during power-up with A/Blow), the DAC code is determined by the resistor
values at D0–D4.
A/B16
Supply Voltage Input for the DL Gate Driver, 4.5V to 5.5V. Bypass to GND with a 1µF capacitor. VDD15
Low-Side Gate Driver Output. DL swings GND to VDD.DL14
2V Reference Output. Bypass to GND with 0.22µF (min) capacitor. Can source 50µA for external loads.
Loading REF degrades FB accuracy according to the REF load-regulation error.REF9
Current-Limit Adjustment. The GND - LX current-limit threshold defaults to 100mV if ILIM is tied to VCC. In
adjustable mode, the current-limit threshold voltage is 1/10th the voltage seen at ILIM over a 0.5V to 3.0V
range. The logic threshold for switchover to the 100mV default value is approximately VCC- 1V. Tie ILIM to
REF for a fixed 200mV threshold.
ILIM10
Ground Remote-Sense Input. For nonvoltage-positioned circuits, connect GNDS to ground directly at the
load. GNDS internally connects to the integrator that fine tunes the output voltage. The output voltage rises
by an amount of GNDS - GND. For voltage-positioned circuits, increase the output voltage (24mV (typ)) by
biasing GNDS with a resistor-divider from REF to GND.
GNDS11
Open-Drain Power-Good Output. VGATE is normally high when the output is in regulation. VGATE goes low
whenever the DAC code changes, and returns high one clock period after the slew-rate controller finishes
and the output is in regulation. VGATE is low in shutdown.
VGATE12
Analog and Power Ground. Also connects to the current-limit comparator.GND13
On-Time Selection Control Input. This is a four-level input that sets the K factor (Table 3) to determine
DH on-time. Connect TON to the following pins for the indicated operation:
GND = 1000kHz
REF = 550kHz
Open = 300kHz
VCC= 200kHz
TON8
PINFUNCTIONNAME
MAX1717
Dynamically Adjustable, Synchronous
Step-Down Controller for Notebook CPUsVCC
VBATT
7V TO 24V
+5V
BIAS SUPPLY
6 x 470μF
KEMET T510
POWER-GOOD
INDICATOR
1μH
A/B = LOW = 1.60V
A/B = HIGH = 1.35V
SKP/SDN22115
CMPSH-3
1μF
0.1μF
1μF
470pF
TO VCC
100kΩ
1μFR1
20ΩC1
4 x 10μF, 25V
TIME
ON/OFF
CONTROL
BST
GND
FBS
GNDS
Q1 = IRF7811
Q2 = 2 x IRF7805
D1 = INTL RECT 10MQ040N
C1 = TAIYO YUDEN TMK432BJ106KM
C2 = KEMET T510X477M006
L1 = SUMIDA CEP125
VGATE
VDD
MAX1717
+5VD4
TON
REF
A/B
ILIM
120kΩ
100kΩ
TO VCC
HIGH/LOW
VOUT
Figure 1. Standard Application Circuit
MAX1717
Dynamically Adjustable, Synchronous
Step-Down Controller for Notebook CPUs
Table 1. Component Selection for Standard ApplicationsGNDREFGNDFloatFloatTON Level
(2) International
Rectifier IRF7805,
IRF7811, or
IRF7811A
(2) International
Rectifier IRF7805,
IRF7811, or
IRF7811A
(2) International
Rectifier IRF7805,
IRF7811, or
IRF7811A
(2) International
Rectifier IRF7805,
IRF7811, or
IRF7811A
(2) International
Rectifier IRF7805,
IRF7811, or
IRF7811A
Low-Side MOSFET
7V to 24V7V to 24V7V to 24V7V to 24VInput Range
(VBATT)4.5V to 5.5V
1000kHz, VOLTAGE
POSITIONED,
CIRCUIT 50.3µH
Sumida
CEP12D38 4713-
T001
5mΩ±1%, 1W
Dale
WSL-2512-R005F
International
Rectifier IRF7811
(4) 10µF, 25V
ceramic
Taiyo Yuden
TMK432BJ106KM
(5) 47µF, 6.3V
ceramic
Taiyo Yuden
JMK432BJ476MM
1000kHz
14A
550kHz, VOLTAGE
POSITIONED,
CIRCUIT 30.47µH
Sumida
CEP125-4712-T006
5mΩ±1%, 1W
Dale
WSL-2512-R005F
International
Rectifier IRF7811
(4) 10µF, 25V
ceramic
Taiyo Yuden
TMK432BJ106KM
(4) 220µF, 2.5V,
25mΩspecialty
polymer
Panasonic
EEFUE0E221R
550kHz
14A
300kHz, VOLTAGE
POSITIONED,
CIRCUIT 2
1000kHz, +5V,
CIRCUIT 40.19µH
Coilcraft
X8357-A
5mΩ±1%, 1W
Dale
WSL-2512-R005F
International
Rectifier IRF7811
(5) 22µF, 10V
ceramic
Taiyo Yuden
LMK432BJ226KM
(5) 47µF, 6.3V
ceramic
Taiyo Yuden
JMK432BJ476MM
1000kHz
14A
24mV24mV
1µH
Sumida
CEP125-1R0MC or
Panasonic
ETQP6F1R1BFA
1µH
Sumida
CEP125-1R0MC or
Panasonic
ETQP6F1R1BFA
Inductor
5mΩ±1%, 1W
Dale
WSL-2512-R005F
Voltage-
Positioning
Resistor R6
24mV24mV—Voltage-
Positioning Offset
International
Rectifier IRF7811
International
Rectifier IRF7811
High-Side MOSFET
(4) 10µF, 25V
ceramic
Taiyo Yuden
TMK432BJ106KM
(4) 10µF, 25V
ceramic
Taiyo Yuden
TMK432BJ106KM
Input Capacitor
(5) 220µF, 2.5V,
25mΩspecialty
polymer
Panasonic
EEFUE0E221R
(6) 470µF, 6.3V
tantalum
Kemet
T510X477M006AS
Output Capacitor
300kHz300kHzFrequency
COMPONENT14A14AOutput Current1Figure Number3
300kHz, STANDARD
APPLICATION,
CIRCUIT 1
MAX1717
Dynamically Adjustable, Synchronous
Step-Down Controller for Notebook CPUs
Detailed Description
+5V Bias Supply (VCCand VDD)The MAX1717 requires an external +5V bias supply in
addition to the battery. Typically, this +5V bias supply
is the notebook’s 95% efficient +5V system supply.
Keeping the bias supply external to the IC improves
efficiency and eliminates the cost associated with the
+5V linear regulator that would otherwise be needed to
supply the PWM circuit and gate drivers. If stand-alone
capability is needed, the +5V supply can be generated
with an external linear regulator.
The +5V bias supply must provide VCC(PWM con-
troller) and VDD(gate-drive power), so the maximum
current drawn is:
IBIAS= ICC+ f (QG1+ QG2) = 10mA to 40mA (typ)
where ICCis 700µA (typ), f is the switching frequency,
and QG1and QG2are the MOSFET data sheet total
gate-charge specification limits at VGS= 5V.
V+ and VDDcan be tied together if the input power
source is a fixed +4.5V to +5.5V supply. If the +5V bias
supply is powered up prior to the battery supply, the
enable signal(SKP/SDNgoing from low to high or
open) must be delayed until the battery voltage is pre-
sent to ensure startup.
Free-Running, Constant On-Time PWM
Controller with Input Feed-ForwardThe Quick-PWM control architecture is a pseudofixed-
frequency, constant-on-time current-mode type with volt-
age feed-forward (Figure 2). This architecture relies on
the output filter capacitor’s ESR to act as the current-
sense resistor, so the output ripple voltage provides the
PWM ramp signal. The control algorithm is simple: the
high-side switch on-time is determined solely by a one-
shot whose period is inversely proportional to input volt-
age and directly proportional to output voltage. Another
one-shot sets a minimum off-time (400ns typ). The on-
time one-shot is triggered if the error comparator is low,
the low-side switch current is below the current-limit
threshold, and the minimum off-time one-shot has timed
out.
On-Time One-Shot (TON)The heart of the PWM core is the one-shot that sets the
high-side switch on-time. This fast, low-jitter, adjustable
one-shot includes circuitry that varies the on-time in
response to battery and output voltage. The high-side
switch on-time is inversely proportional to the battery
voltage as measured by the V+ input, and proportional
to the output voltage. This algorithm results in a nearly
constant switching frequency despite the lack of a
fixed-frequency clock generator. The benefits of a con-
stant switching frequency are twofold: first, the frequency
can be selected to avoid noise-sensitive regions such
as the 455kHz IF band; second, the inductor ripple-cur-
rent operating point remains relatively constant, resulting
in easy design methodology and predictable output
voltage ripple.
On-Time = K (VOUT+ 0.075V) / VIN
where K is set by the TON pin-strap connection and
0.075V is an approximation to accommodate the expect-
ed drop across the low-side MOSFET switch (Table 3).
The on-time one-shot has good accuracy at the operating
points specified in the Electrical Characteristics (±10% at
200kHz and 300kHz, ±12% at 550kHz and 1000kHz).
On-times at operating points far removed from the condi-
tions specified in the Electrical Characteristics can vary
over a wide range. For example, the 1000kHz setting will
typically run about 10% slower with inputs much greater
than +5V due to the very short on-times required.
On-times translate only roughly to switching frequencies.
The on-times guaranteed in the Electrical Character-
istics are influenced by switching delays in the external
high-side MOSFET. Resistive losses, including the
inductor, both MOSFETs, output capacitor ESR, and PC
board copper losses in the output and ground tend to
raise the switching frequency at higher output currents.
Table 2. Component Suppliers
Table 3. Approximate K-Factors Errors±10
TON
SETTING
(kHz)
APPROXIMATE
K-FACTOR
ERROR (%)
MIN RECOMMENDED
VBATTATVOUT= 1.6V
(V)200±102.1
550±12.53.2
1000±12.54.5
FACTOR
(µs)MANUFACTURERUSA PHONEFACTORY FAX
[Country Code]
Coilcraft847-639-6400[1] 847-639-1469
Dale-Vishay402-564-3131[1] 402-563-6418
[1] 310-322-3332310-322-3331International Rectifier
Kemet408-986-0424[1] 408-986-1442
[1] 714-373-7183714-373-7939Panasonic
[81] 3-3607-5144847-956-0666
408-573-4150[1] 408-573-4159
Sumida
Taiyo Yuden
MAX1717
Dynamically Adjustable, Synchronous
Step-Down Controller for Notebook CPUsREF
-7%
FROM
D/A
REF
REFA/BD1D2D3D4TIME
10k
ERROR
AMP
TOFF
TON
REF
+12%
R-2R
D/A CONVERTER
CHIP SUPPLYgmgm
GNDS
FBS
VGATE
ON-TIME
COMPUTE
TON
1-SHOT
1-SHOT
TRIG
VBATT
2V TO 28V
TRIG
REF
REF
GND
+5V
OUTPUT
VCC
VDD
ZERO CROSSING
CURRENT
LIMIT
BST
ILIM
REF
+5V
+5V
OVP/UVP
DETECT
SKP/SDN
TON
70k
MAX1717
120k
MUX AND SLEW CONTROL1
Figure 2. Functional Diagram
MAX1717
Dynamically Adjustable, Synchronous
Step-Down Controller for Notebook CPUsThe dead-time effect increases the effective on-time,
reducing the switching frequency. It occurs only in
PWM mode (SKP/SDN= open) and dynamic output
voltage transitions when the inductor current reverses
at light or negative load currents. With reversed inductor
current, the inductor’s EMF causes LX to go high earlier
than normal, extending the on-time by a period equal to
the DH-rising dead time.
For loads above the critical conduction point, where the
dead-time effect is no longer a factor, the actual switching
frequency is:
f = (VOUT+ VDROP1) / tON(VIN+ VDROP1 - VDROP2)
where VDROP1is the sum of the parasitic voltage drops
in the inductor discharge path, including synchronous
rectifier, inductor, and PC board resistances; VDROP2is
the sum of the parasitic voltage drops in the inductor
charge path, including high-side switch, inductor, and
PC board resistances; tONis the on-time calculated by
the MAX1717.
Integrator AmplifiersThree integrator amplifiers provide a fine adjustment to
the output regulation point. One amplifier integrates the
difference between GNDS and GND, a second inte-
grates the difference between FBS and FB. The third
amplifier integrates the difference between REF and the
DAC output. These three transconductance amplifiers’
outputsare directly summed inside the chip, so the
integration time constant can be set easily with one
capacitor. The gmof each amplifier is 160µS (typ).
The integrator block has the ability to lower the output
voltage by 2% and raise it by 6%. For each amplifier, the
differential input voltage range is at least ±70mV total,
including DC offset and AC ripple. The integrator corrects
for approximately 90% of the total error, due to finite gain.
The FBS amplifier corrects for DC voltage drops in PC
board traces and connectors in the output bus path
between the DC-DC converter and the load. The GNDS
amplifier performs a similar DC correction task for the
output ground bus. The third integrator amplifier cor-
rects the small offset of the error amplifier and provides
an averaging function that forces VOUTto be regulated
at the average value of the output ripple waveform.
Integrators have both beneficial and detrimental char-
acteristics. Although they correct for drops due to DC
bus resistance and tighten the DC output voltage toler-
ance limits by averaging the peak-to-peak output ripple,
they can interfere with achieving the fastest possible
load-transient response. The fastest transient response
is achieved when all three integrators are disabled.
This can work very well if the MAX1717 circuit is placed
very close to the CPU.
All three integrators can be disabled by connecting
FBS to VCC. When the integrators are disabled, CC can
be left unconnected, which eliminates a component,
but leaves GNDS connected to any convenient ground.
When the inductor is in continuous conduction, the output
voltage will have a DC regulation higher than the trip
level by 50% of the ripple. In discontinuous conduction
(SKP/SDNopen, light-loaded), the output voltage will
have a DC regulation higher than the trip level by
approximately 1.5% due to slope compensation.
There is often a connector, or at least many milliohms of
PC board trace resistance, between the DC-DC con-
verter and the CPU. In these cases, the best strategy is
to place most of the bulk bypass capacitors close to
the CPU, with just one capacitor on the other side of the
connector near the MAX1717 to control ripple if the
CPU card is unplugged. In this situation, the remote-
sense lines (GNDS and FBS) and integrators provide a
real benefit.
When operating the MAX1717 in a voltage-positioned
circuit (Figure 3), GNDS can be offset with a resistor
divider from REF to GND, which causes the GNDS inte-
grator to increase the output voltage by 90% of the
applied offset (27mV typ). A low-value (5mΩtyp) voltage-
positioning resistor is added in series between the
external inductor and the output capacitor. FBS is con-
nected to FB directly at the junction of the external
inductor and the voltage-positioning resistor. The net
effect of these two changes is an output voltage that is
slightly higher than the programmed DAC voltage at
light loads, and slightly less than the DAC voltage at
full-load current. For further information on voltage-posi-
tioning,see the Applicationssection.
Automatic Pulse-Skipping SwitchoverIn skip mode (SKP/SDNhigh), an inherent automatic
switchover to PFM takes place at light loads (Figure 4).
This switchover is effected by a comparator that trun-
cates the low-side switch on-time at the inductor current’s
zero crossing. This mechanism causes the threshold
between pulse-skipping PFM and nonskipping PWM
operation to coincide with the boundary between con-
tinuous and discontinuous inductor-current operation
(see the Continuous-to-Discontinuous Inductor Current
Point graph in the Typical Operating Characteristics).
MAX1717
Dynamically Adjustable, Synchronous
Step-Down Controller for Notebook CPUsFor a battery range of 7V to 24V, this threshold is rela-
tively constant, with only a minor dependence on bat-
tery voltage:
where K is the on-time scale factor (Table 3). The load-
current level at which PFM/PWM crossover occurs,
ILOAD(SKIP), is equal to 1/2 the peak-to-peak ripple cur-
rent, which is a function of the inductor value (Figure 4).
For example, in the standard application circuit this
becomes:
The crossover point occurs at an even lower value if a
swinging (soft-saturation) inductor is used.
The switching waveforms may appear noisy and asyn-
chronous when light loading causes pulse-skipping
operation, but this is a normal operating condition that
results in high light-load efficiency. Trade-offs in PFM
noise vs. light-load efficiency are made by varying the
inductor value. Generally, low inductor values produce
a broader efficiency vs. load curve, while higher values
result in higher full-load efficiency (assuming that the
coil resistance remains fixed) and less output voltage
ripple. Penalties for using higher inductor values
include larger physical size and degraded load-tran-
sient response (especially at low input voltage levels).161623. . . . μA××=−KVLOADSKIPOUTBATTOUT
BATT() ≈××−
VCC
VBATT
+5V
BIAS SUPPLY
POWER-GOOD
INDICATOR
1μH
0.005Ω
SKP/SDN22115D2
CMPSH-3
1μF
0.1μF
1μF
470pF
TO VCC
100kΩ
1μFR1
20Ω
C1
TIME
ON/OFF
CONTROL
BST
GND
FBS
GNDS
D1 = INTL RECT 10MQ040N.
FOR OTHER COMPONENTS,
SEE TABLE 1 VALUES.
VGATE
VDD
MAX1717
+5VD4
TON
REF
A/B
ILIM
120kΩ
100kΩ
TO VCC
HIGH/LOW
2kΩ
150kΩ
TO VREF
A/B = LOW = 1.60V
A/B = HIGH = 1.35V
VOUT
Figure 3. Voltage-Positioned Circuit
