MAX1711EEG ,High-Speed / Digitally Adjusted Step-Down Controllers for Notebook CPUsFeaturesThe MAX1710/MAX1711 step-down controllers are' Ultra-High Efficiency intended for core CPU ..
MAX1711EEG ,High-Speed / Digitally Adjusted Step-Down Controllers for Notebook CPUsELECTRICAL CHARACTERISTICS(Circuit of Figure 1, V = 15V, V = V = 5V, SKIP = GND, T = 0°C to +85°C, ..
MAX1711EEG+ ,High-Speed, Digitally Adjusted Step-Down Controllers for Notebook CPUsELECTRICAL CHARACTERISTICS(Circuit of Figure 1, V = 15V, V = V = 5V, SKIP = GND, T = 0°C to +85°C, ..
MAX1711EEG-T ,High-Speed, Digitally Adjusted Step-Down Controllers for Notebook CPUsMAX1710/MAX1711/MAX171219-4781; Rev 1; 7/00High-Speed, Digitally AdjustedStep-Down Controllers for ..
MAX17121ETG+ ,Dual High-Voltage Scan Drivers for TFT LCDELECTRICAL CHARACTERISTICS(V = V = +3.3V, V = 25V, V = -15V, STV = CPV1 = CPV2 = GND, T = 0NC to +8 ..
MAX17121ETG+T ,Dual High-Voltage Scan Drivers for TFT LCDFeaturesThe MAX17121 includes two high-voltage level-shifting S +40V to -30V Output Swing Rangescan ..
MAX453CSA+ ,50MHz Video Amplifier and Mux AmpsGeneral Description
The MAX452 is a unity-gain stable, 50MHz video amplifier
capable of driving ..
MAX453EPA ,CMOS Video Multiplexer/AmplifierApplications
Video signal multiplexing
75 ohm cable drivers
Driving flash converters
Video Cros ..
MAX453MJA/883B ,50MHz Video Amplifier and Mux Ampsapplications, these amprfers will
directly drive a 150 ohm load to bN, and will swing k11/
into a ..
MAX4541CPA ,Low-Voltage, Single-Supply Dual SPST/SPDT Analog SwitchesMAX4541–MAX454419-1202; Rev 3; 8/02Low-Voltage, Single-Supply Dual SPST/SPDT Analog Switches
MAX4541CSA ,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 ..
MAX4541CSA ,Low-Voltage, Single-Supply Dual SPST/SPDT Analog SwitchesApplicationsMAX4541CUA 0°C to +70°C 8 µMAX —Battery-Operated Systems Test EquipmentMAX4541CSA 0 ..
MAX1710EEG-MAX1711EEG
High-Speed / Digitally Adjusted Step-Down Controllers for Notebook CPUs
General DescriptionThe MAX1710/MAX1711 step-down controllers are
intended for core CPU DC-DC converters in notebook
computers. They feature a triple-threat combination of
ultra-fast transient 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 fre-
quency.
High DC precision is ensured by a 2-wire remote-sens-
ing scheme that compensates for voltage drops in both
ground bus and the supply rail. An on-board, digital-to-
analog converter (DAC) sets the output voltage in com-
pliance with Mobile Pentium II®CPU specifications.
The MAX1710 achieves high efficiency at a reduced
cost by eliminating the current-sense resistor found in
traditional current-mode PWMs. Efficiency is further
enhanced by an ability to drive very large synchronous-
rectifier MOSFETs.
Single-stage buck conversion allows these devices to
directly step down high-voltage batteries for the highest
possible efficiency. Alternatively, 2-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 MAX1710 and MAX1711 are identical except that
the MAX1711 has a 5-bit DAC rather than a 4-bit DAC.
Also, the MAX1711 has a fixed overvoltage protection
threshold at VOUT= 2.25V and undervoltage protection
at VOUT= 0.8V, whereas the MAX1710 has variable
thresholds that track VOUT. The MAX1711 is intended
for applications where the DAC code may change
dynamically.
ApplicationsNotebook Computers
Docking Stations
CPU Core DC-DC Converters
Single-Stage (BATT to VCORE)Converters
Two-Stage (+5V to VCORE) Converters
FeaturesUltra-High Efficiency No Current-Sense Resistor (Lossless ILIMIT)QUICK-PWM with 100ns Load-Step Response±1% VOUTAccuracy over Line and Load4-Bit On-Board DAC (MAX1710)5-Bit On-Board DAC(MAX1711)0.925V to 2V Output Adjust Range (MAX1711)2V to 28V Battery Input Range 200/300/400/550kHz Switching FrequencyRemote GND and VOUTSensingOver/Undervoltage Protection1.7ms Digital Soft-StartDrives Large Synchronous-Rectifier FETs2V ±1% Reference Output Power-Good IndicatorSmall 24-Pin QSOP Package
MAX1710/MAX1711
High-Speed, Digitally Adjusted
Step-Down Controllers for Notebook CPUs
Pin Configuration appears at end of data sheet.QUICK-PWM is a trademark of Maxim Integrated Products.
Mobile Pentium II is a registered trademark of Intel Corp.
Ordering Information
Minimal Operating Circuit
MAX1710/MAX1711
High-Speed, Digitally Adjusted
Step-Down Controllers for Notebook CPUs
ABSOLUTE MAXIMUM RATINGSStresses 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
PGND to GND.....................................................................±0.3VSHDN, PGOOD to GND...........................................-0.3V to +6V
OVP,ILIM, FB, FBS, CC, REF, D0–D4,
GNDS, TON to GND..............................-0.3V to (VCC+ 0.3V)
SKIPto GND (Note 1).................................-0.3V to (VCC+ 0.3V)
DL to PGND................................................-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 (TA= +70°C)
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 Range.............................-65°C to +165°C
Lead Temperature (soldering, 10sec).............................+300°C
Note 1:SKIPmay be forced below -0.3V, temporarily exceeding the absolute maximum rating, for the purpose of debugging proto-
type breadboards using the no-fault test mode. Limit the current drawn to -5mA maximum.
ELECTRICAL CHARACTERISTICS(Circuit of Figure 1, VBATT= 15V, VCC= VDD= 5V, SKIP= GND, TA= 0°C to +85°C, unless otherwise noted.)
MAX1710/MAX1711
High-Speed, Digitally Adjusted
Step-Down Controllers for Notebook CPUs
ELECTRICAL CHARACTERISTICS (continued)(Circuit of Figure 1, VBATT= 15V, VCC= VDD= 5V, SKIP= GND, TA= 0°C to +85°C, unless otherwise noted.)
MAX1710/MAX1711
High-Speed, Digitally Adjusted
Step-Down Controllers for Notebook CPUs
ELECTRICAL CHARACTERISTICS (Circuit of Figure 1, VBATT=15V, VCC = VDD= 5V, SKIP= GND, TA
= -40°C to +85°C,unless otherwise noted.) (Note 3)
ELECTRICAL CHARACTERISTICS (continued)(Circuit of Figure 1, VBATT= 15V, VCC= VDD= 5V, SKIP= GND, TA= 0°C to +85°C, unless otherwise noted.)
MAX1710/MAX1711
High-Speed, Digitally Adjusted
Step-Down Controllers for Notebook CPUs
Note 2:On-Time and Off-Time specifications are measured from 50% point to 50% point at the DH pin with LX forced to 0V, BST
forced to 5V, and a 250pF capacitor connected from DH to LX. Actual in-circuit times may differ due to MOSFET switching
speeds.
Note 3:Specifications from -40°C to 0°C are guaranteed but not production tested.
__________________________________________Typical Operating Characteristics(7A CPU supply circuit of Figure 1, TA= +25°C, unless otherwise noted.)
ELECTRICAL CHARACTERISTICS (continued)(Circuit of Figure 1, VBATT=15V, VCC = VDD= 5V, SKIP= GND, TA
= -40°C to +85°C,unless otherwise noted.) (Note 3)
MAX1710/MAX1711
High-Speed, Digitally Adjusted
Step-Down Controllers for Notebook CPUs
_____________________________Typical Operating Characteristics (continued)
MAX1710/MAX1711
High-Speed, Digitally Adjusted
Step-Down Controllers for Notebook CPUs
_____________________________Typical Operating Characteristics (continued)(7A CPU supply circuit of Figure 1, TA= +25°C, unless otherwise noted.)
MAX1710/MAX1711
High-Speed, Digitally Adjusted
Step-Down Controllers for Notebook CPUs
_____________________________Typical Operating Characteristics (continued)
Pin Description
MAX1710/MAX1711
High-Speed, Digitally Adjusted
Step-Down Controllers for Notebook CPUs
Standard Application CircuitThe standard application circuit (Figure 1) generates a
low-voltage, high-power rail for supplying up to 7A to the
core CPU VCCin a notebook computer. This DC-DC
converter steps down a battery or AC adapter voltage to
sub-2V levels with high efficiency and accuracy, and
represents a good compromise between size, efficiency,
and cost.
See the MAX1710 EV kit manual for a list of components
and suppliers.
Detailed DescriptionThe MAX1710/MAX1711 buck controllers are targeted
for low-voltage, high-current CPU power supplies for
notebook computers. CPU cores typically exhibit 0 to
10A or greater load steps when the clock is throttled.
The proprietary QUICK-PWM pulse-width modulator in
the MAX1710/MAX1711 is specifically designed for han-
dling these fast load steps while maintaining a relatively
constant operating frequency and inductor operating
point over a wide range of input voltages. The QUICK-
PWM architecture circumvents the poor load-transient
timing problems of fixed-frequency current-mode PWMs
Pin Description (continued)
MAX1710/MAX1711while also avoiding the problems caused by widely vary-
ing switching frequencies in conventional constant-on-
time and constant-off-time PWM schemes.
+5V Bias Supply (VCCand VDD)The MAX1710/MAX1711 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 effi-
ciency and eliminates the cost associated with the +5V
linear regulator that would otherwise be needed to sup-
ply the PWM circuit and gate drivers. If stand-alone
capability is needed, the +5V supply can be generated
with an external linear regulator such as the MAX1615.
The battery and +5V bias inputs can be tied together if
the input 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 (SHDN) must be delayed until the battery
voltage is present in order to ensure start-up. The +5V
bias supply must provide VCCand gate-drive power, so
the maximum current drawn is:
IBIAS= ICC+ f ·(QG1+ QG2) = 15mA to 30mA (typ)
High-Speed, Digitally Adjusted
Step-Down Controllers for Notebook CPUsFigure 1. Standard Application Circuit
where ICCis 600µA typical, f is the switching frequency,
and QG1and QG2are the MOSFET data sheet total
gate-charge specification limits at VGS= 5V.
Free-Running, Constant-On-Time PWM
Controller with Input Feed-ForwardThe QUICK-PWM control architecture is an almost fixed-
frequency, constant-on-time current-mode type with volt-
age feed-forward (Figure 2). This architecture relies on
the 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 voltage
and directly proportional to output voltage. Another one-
shot sets a minimum off-time (400ns typical). The on-time
one-shot is triggered if the error comparator is low, the
MAX1710/MAX1711
High-Speed, Digitally Adjusted
Step-Down Controllers for Notebook CPUsFigure 2. MAX1710 Functional Diagram
MAX1710/MAX1711
High-Speed, Digitally Adjusted
Step-Down Controllers for Notebook CPUslow-side switch current is below the current-limit thresh-
old, 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 directly pro-
portional to the output voltage as set by the DAC code.
This algorithm results in a nearly constant switching fre-
quency despite the lack of a fixed-frequency clock gen-
erator. The benefits of a constant 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-current 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 for the
expected drop across the low-side MOSFET switch.
One-shot timing error increases for the shorter on-time
settings due to fixed propagation delays and is approxi-
mately ±12.5% at 550kHz and 400kHz, and ±10% at the
two slower settings. This translates to reduced switch-
ing-frequency accuracy at higher frequencies. (see
Table 5). Switching frequency increases as a function of
load current due to the increasing drop across the low-
Table 1. MAX1710 FBOutput Voltage
DAC Codes
Table 2. MAX1711 FBOutput Voltage
DAC Codes
MAX1710/MAX1711
High-Speed, Digitally Adjusted
Step-Down Controllers for Notebook CPUsside MOSFET, which causes a faster inductor-current
discharge ramp. The on-times guaranteed in the
Electrical Characteristics are influenced by switching
delays in the external high-side power MOSFET. The
exact switching frequency will depend on gate charge,
internal gate resistance, source inductance, and DH out-
put drive characteristics.
Two external factors that can influence switching-fre-
quency accuracy are resistive drops in the two conduc-
tion loops (including inductor and PC board resistance)
and the dead-time effect. These effects are the largest
contributors to the change of frequency with changing
load current. The dead-time effect is a notable disconti-
nuity in the switching frequency as the load current is
varied (see Typical Operating Characteristics). It occurs
whenever the inductor current reverses, most commonly
at light loads with SKIPhigh. With reversed inductor cur-
rent, the inductor’s EMF causes LX to go high earlier
than normal, extending the on-time by a period equal to
the low-to-high dead time. For loads above the critical
conduction point, the actual switching frequency is:
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 resistances in the charging path, and tON
is the on-time calculated by the MAX1710/MAX1711.
Integrator Amplifiers (CC)There are three integrator amplifiers that provide a fine
adjustment to the output regulation point. One amplifier
monitors the difference between GNDS and GND, while
another monitors the difference between FBS and FB.
The third amplifier integrates the difference between REF
and the DAC output. These three transconductance
amplifiers’ outputs are directly summed inside the chip,
so the integration time constant can be set easily with a
capacitor. The gmof each amplifier is 160µmho (typical).
The integrator block has an ability to move and correct
the output voltage by about -2%, +4%. For each amplifi-
er, the differential input voltage range is about ±50mV
total, including DC offset and AC ripple. The voltage
gain of each integrator is about 80V/V.
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 amplifier provides an aver-
aging function that forces VOUTto be regulated at the
average value of the output ripple waveform. If the inte-
grator amplifiers are disabled, VOUTis regulated at the
valleys of the output ripple waveform. This creates a
slight load-regulation characteristic in which the output
voltage rises approximately 1% (up to 1/2 the peak
amplitude of the ripple waveform as a limit) when under
light loads.
Integrators have both beneficial and detrimental charac-
teristics. While they do correct for drops due to DC bus
resistance and tighten the DC output voltage tolerance
limits by averaging the peak-to-peak output
ripple, they can interfere with achieving the fastest possi-
ble load-transient response. The fastest transient
response is achieved when all three integrators are dis-
abled. This works very well when the MAX1710/
MAX1711 circuit can be placed very close to the CPU.
There is often a connector, or at least many milliohms of
PC board trace resistance, between the DC-DC convert-
er 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 MAX1710/MAX1711 to control ripple
if the CPU card is unplugged. In this situation, the
remote-sense lines and integrators provide a real benefit.
When both GNDS and FBS are tied to VCCso that all
three integrators are disabled, CC can be left uncon-
nected, which eliminates a component.
Automatic Pulse-Skipping SwitchoverAt light loads, an inherent automatic switchover to PFM
takes place. This switchover is effected by a comparator
that truncates the low-side switch on-time at the inductor
current’s zero crossing. This mechanism causes the
threshold between pulse-skipping PFM and non-skip-
ping PWM operation to coincide with the boundary
between continuous and discontinuous inductor-current
operation (also known as the “critical conduction” point;
see Continuous to Discontinuous Inductor Current Point
vs. Input Voltage graphs in the Typical Operating
Characteristics). For a battery range of 7V to 24V this
threshold is relatively constant, with only a minor depen-
dence on battery voltage.
where K is the On-Time Scale factor (see Table 5). 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 3).
For example, in the standard application circuit with tON
= 300ns at 24V, VOUT= 2V, and L = 2µH, switchover to
pulse-skipping operation occurs at ILOAD= 1.65A or
MAX1710/MAX1711
High-Speed, Digitally Adjusted
Step-Down Controllers for Notebook CPUsFigure 4. ‘‘Valley’’ Current-Limit Threshold Point
about 1/4 full load. 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 can be made by varying
the inductor value. Generally, low inductor values pro-
duce 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-transient
response (especially at low input voltage levels).
Forced-PWM Mode (SSKKIIPP = High)
The low-noise, forced-PWM mode (SKIPdriven high) dis-
ables the zero-crossing comparator, which controls the
low-side switch on-time. This causes the low-side gate-
drive waveform to become the complement of the high-
side gate-drive waveform. This in turn causes the
inductor current to reverse at light loads, as the PWM
loop strives to maintain a duty ratio of VOUT/VIN. The
benefit of forced-PWM mode is to keep the switching fre-
quency fairly constant, but it comes at a cost: the no-
load battery current can be as high as 40mA or more.
Forced-PWM mode is most useful for reducing audio-fre-
quency noise, improving load-transient response, pro-
viding sink-current capability for dynamic output voltage
adjustment, and improving the cross-regulation of multi-
ple-output applications that use a flyback transformer or
coupled inductor.
Current-Limit Circuit (ILIM)The current-limit circuit employs a unique “valley” cur-
rent-sensing algorithm that uses the on-state resistance
of the low-side MOSFET as a current-sensing element. If
the current-sense signal is above the current-limit
threshold, the PWM is not allowed to initiate a new cycle
(Figure 4). The actual peak current is greater than the
current-limit threshold by an amount equal to the induc-
tor ripple current. Therefore the exact current-limit char-
acteristic and maximum load capability are a function of
the MOSFET on-resistance, inductor value, and battery
voltage. The reward for this uncertainty is robust, loss-
less overcurrent sensing. When combined with the UVP
protection circuit, this current-limit method is effective in
almost every circumstance.
There is also a negative current limit that prevents exces-
sive reverse inductor currents when VOUTis sinking cur-
rent. The negative current-limit threshold is set to
approximately 120% of the positive current limit, and
therefore tracks the positive current limit when ILIM is
adjusted.
The current-limit threshold can be adjusted with an exter-
nal resistor (RLIM) at ILIM. A precision 5µA pull-up cur-
rent source at ILIM sets a voltage drop on this resistor,
adjusting the current-limit threshold from 50mV to
200mV. In the adjustable mode, the current-limit thresh-
old voltage is precisely 1/10th the voltage seen at ILIM.
Therefore, choose RLIMequal to 2kΩ/mV of the current-
limit threshold. The threshold defaults to 100mV when
ILIM is tied to VCC. The logic threshold for switchover to
the 100mV default value is approximately VCC- 1V.
The adjustable current limit can accommodate
MOSFETs with atypical on-resistance characteristics
(see Design Procedure).
A capacitor in parallel with RLIM can provide a variable
soft-start function.
Carefully observe the PC board layout guidelines to
ensure that noise and DC errors don’t corrupt the cur-
rent-sense signals seen by LX and PGND. The IC must
be mounted close to the low-side MOSFET with short,
Figure 3. Pulse-Skipping/Discontinuous Crossover Point
