MAX1717EEG ,Dynamically Adjustable / Synchronous Step-Down Controller for Notebook CPUsApplications100ns “instant-on” response to load transients while 2V to 28V Battery Input Range mai ..
MAX1717EEG ,Dynamically Adjustable / Synchronous Step-Down Controller for Notebook CPUsELECTRICAL CHARACTERISTICS(Circuit of Figure 1, V+ = +15V, V = V = SKP/SDN = +5V, V = 1.6V, T = 0°C ..
MAX1717EEG ,Dynamically Adjustable / Synchronous Step-Down Controller for Notebook CPUsApplicationsFBSBSTNotebook Computers with SpeedStep™ or OtherILIMDHDynamically Adjustable Processor ..
MAX1717EEG+ ,Dynamically Adjustable, Synchronous Step-Down Controller for Notebook CPUsApplicationsinput/output voltage ratios with ease and provides100ns “instant-on” response to load t ..
MAX1717EEG-T ,Dynamically Adjustable, Synchronous Step-Down Controller for Notebook CPUsFeaturesThe MAX1717 step-down controller is intended for core♦ Quick-PWM Architecture CPU DC-DC co ..
MAX1717EEG-T ,Dynamically Adjustable, Synchronous Step-Down Controller for Notebook CPUsApplicationsFBSBSTNotebook Computers with SpeedStep™ or ILIMDHOther Dynamically Adjustable Processo ..
MAX4544EUT-T ,Low-Voltage, Single-Supply Dual SPST/SPDT Analog SwitchesFeaturesThe MAX4541–MAX4544 are precision, dual analog Low R : 60Ω max (33Ω typ)ONswitches design ..
MAX4544EUT-T ,Low-Voltage, Single-Supply Dual SPST/SPDT Analog SwitchesApplicationsMAX4541CUA 0°C to +70°C 8 µMAX —Battery-Operated Systems Test EquipmentMAX4541CSA 0 ..
MAX4544EUT-T ,Low-Voltage, Single-Supply Dual SPST/SPDT Analog SwitchesELECTRICAL CHARACTERISTICS—Single +5V Supply(V+ = +5V ±10%, GND = 0, V = 2.4V, V = 0.8V, T = T to T ..
MAX4544EUT-T ,Low-Voltage, Single-Supply Dual SPST/SPDT Analog SwitchesFeaturesThe MAX4541–MAX4544 are precision, dual analog Low R : 60Ω max (33Ω typ)ONswitches design ..
MAX4544EUT-T ,Low-Voltage, Single-Supply Dual SPST/SPDT Analog SwitchesApplicationsMAX4541CUA 0°C to +70°C 8 µMAX —Battery-Operated Systems Test EquipmentMAX4541CSA 0 ..
MAX4545CAP ,Quad/Dual, Low-Voltage, Bidirectional RF/Video SwitchesGeneral Description ________
MAX1717EEG
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
Step-Down Controller for Notebook CPUs
Ordering Information
Pin Configuration appears at end of data sheet.†Patent pending.
Quick-PWM is a trademark of Maxim Integrated Products.
SpeedStep is a trademark of Intel Corp.
Minimal Operating Circuit
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
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.)
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)
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)
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.
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.)
MAX1717
Dynamically Adjustable, Synchronous
Step-Down Controller for Notebook CPUs
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
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
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.)
MAX1717
Dynamically Adjustable, Synchronous
Step-Down Controller for Notebook CPUs
Pin Description (continued)
MAX1717
Dynamically Adjustable, Synchronous
Step-Down Controller for Notebook CPUs
Figure 1. Standard Application Circuit
MAX1717
Dynamically Adjustable, Synchronous
Step-Down Controller for Notebook CPUs
Table 1. Component Selection for Standard Applications
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-Forward
The Quick-PWM control architecture is a pseudofixed-
frequency, constant-on-time current-mode type with
voltage 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 comparatoris 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 table
(±10% at 200kHz and 300kHz, ±12% at 550kHz and
1000kHz). On-times at operating points far removed from
the conditions specified in the Electrical Characteristics
table 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 table are influenced by switching delays in the
MAX1717
Dynamically Adjustable, Synchronous
Step-Down Controller for Notebook CPUs
Figure 2. Functional Diagram
MAX1717
Dynamically Adjustable, Synchronous
Step-Down Controller for Notebook CPUs
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. The 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 inductorcurrent, 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:
ƒ = (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; and tONis the on-time calculat-
ed by the MAX1717.
Integrator Amplifiers
Three 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 160µmho (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 Switchover
In 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).
For a battery range of 7V to 24V, this threshold is rela-
tively constant, with only a minor dependence on bat-
tery voltage:
