MAX1761EEE ,Small, Dual, High-Efficiency Buck Controller for NotebooksELECTRICAL CHARACTERISTICS(Circuit of Figure 1, V+ = 15V, C = 4.7µF, C = 0.1µF, VL not externally d ..
MAX1761EEE ,Small, Dual, High-Efficiency Buck Controller for NotebooksApplicationsNotebooks and PDAsTOP VIEWDigital CamerasFB1 1 16 DH1Handy-TerminalsOUT1 2 15 CS1Smart ..
MAX1761EEE ,Small, Dual, High-Efficiency Buck Controller for Notebooksapplications, such as Flexible Output Voltagesnotebook computers and smart phones. OUT1: Dual Mode ..
MAX1761EEE+ ,Small, Dual, High-Efficiency Buck Controller for Notebooksapplications, such as♦ Flexible Output Voltagesnotebook computers and smart phones. OUT1: Dual Mode ..
MAX1762EUB ,High-Efficiency, 10-Pin レMAX, Step-Down Controllers for NotebooksApplications PART TEMP. RANGE PIN-PACKAGE Notebooks Handy-TerminalsMAX1762EUB -40°C to +85°C 10 µMA ..
MAX1762EUB ,High-Efficiency, 10-Pin レMAX, Step-Down Controllers for NotebooksMAX1762/MAX179119-1923; Rev 0; 1/01High-Efficiency, 10-Pin µMAX, Step-Down Controllers for Notebooks
MAX4586EUB ,Serially Controlled / 4-Channel Audio/Video MultiplexersELECTRICAL CHARACTERISTICS—Single +5V Supply(V+ = +5V ±5%, T = T to T , unless otherwise noted. Typ ..
MAX4586EUB ,Serially Controlled / 4-Channel Audio/Video MultiplexersApplications Ordering InformationCellular Phones and AccessoriesPART TEMP. RANGE PIN-PACKAGEMAX4586 ..
MAX4586EUB+ ,Serially Controlled, 4-Channel Audio/Video MultiplexersApplications Ordering InformationCellular Phones and AccessoriesPART TEMP. RANGE PIN-PACKAGEMAX4586 ..
MAX4586EUB+T ,Serially Controlled, 4-Channel Audio/Video MultiplexersELECTRICAL CHARACTERISTICS—Single +5V Supply(V+ = +5V ±5%, T = T to T , unless otherwise noted. Typ ..
MAX4588 ,Low-Voltage, High-Isolation, Dual 4-Channel RF Video MultiplexerApplicationsInterfaceRF Switching Automatic Test Equipment♦ >±2kV ESD Protection per Method 3015.7V ..
MAX4588CAI ,Low-Voltage, High-Isolation, Dual 4-Channel RF/Video MultiplexerELECTRICAL CHARACTERISTICS—Dual Supplies(V+ = V = +4.5V to +5.5V, V- = -4.5V to -5.5V, V = +2.4V, V ..
MAX1761EEE
Small, Dual, High-Efficiency Buck Controller for Notebooks
General DescriptionThe MAX1761 dual pulse-width-modulation (PWM),
step-down controller provides high efficiency, excellent
transient response, and high DC output accuracy in an
extremely compact circuit topology. These features are
essential for stepping down high-voltage batteries to
generate low-voltage CPU core, I/O, and chipset RAM
supplies in PC board area critical applications, such as
notebook computers and smart phones.
Maxim’s proprietary Quick-PWM™ quick-response,
constant-on-time PWM control scheme handles wide
input/output voltage ratios with ease and provides
“instant-on” response to load transients while maintain-
ing a relatively constant switching frequency.
The MAX1761 achieves high efficiency at reduced cost
by eliminating the current-sense resistor found in tradi-
tional current-mode PWMs. Efficiency is further
enhanced by its ability to drive large synchronous-recti-
fier MOSFETs. The MAX1761 employs a complemen-
tary MOSFET output stage, which reduces component
count by eliminating external bootstrap capacitors and
diodes.
Single-stage buck conversion allows this device 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 MAX1761 is intended for CPU core, chipset,
DRAM, or other low-voltage supplies. The MAX1761 is
available in a 16-pin QSOP package. For applications
requiring greater output power, refer to the MAX1715
data sheet. For a single-output version, refer to the
MAX1762/MAX1791 data sheet.
________________________ApplicationsNotebooks and PDAs
Digital Cameras
Handy-Terminals
Smart Phones
1.8V/2.5V Logic and I/O Supplies
FeaturesFree-Running On-Demand PWMSelectable Light-Load Pulse-Skipping Operation ±1% Total DC Error in Forced-PWM Mode5V to 20V Input RangeFlexible Output Voltages
OUT1: Dual Mode™Fixed 2.5V or 1V to 5.5V
Adjustable
OUT2: Dual Mode Fixed 1.8V or 1V to 5.5V
AdjustableOutput Undervoltage Protection Complementary Synchronous BuckNo Current-Sense Resistor4.65V at 25mA Linear Regulator Output 4µA V+ Shutdown Supply Current5µA VL Shutdown Supply Current950µA Quiescent Supply CurrentTiny 16-Pin QSOP Package
MAX1761
Small, Dual, High-Efficiency
Buck Controller for Notebooks
Pin Configuration19-1835; Rev 0; 10/00
Ordering InformationQuick-PWM and Dual Mode are trademarks of
Maxim Integrated Products.
MAX1761
Small, Dual, High-Efficiency
Buck Controller for Notebooks
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS(Circuit of Figure 1, V+ = 15V, CVL= 4.7µF, CREF= 0.1µF, VL not externally driven unless otherwise noted, TA
= 0°C to +85°C, unlessotherwise noted.) (Note 1)
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 +22V
VL to GND................................................................-0.3V to +6V
VL to V+ .............................................................................+0.3V
OUT_, ON2 to GND..................................................-0.3V to +6V
ON1, DH_ to GND........................................-0.3V to (V+ + 0.3V)
FB_, REF, DL_ to GND.................................-0.3V to (VL + 0.3V)
CS_ to GND.....................................................-2V to (V+ + 0.3V)
REF Short Circuit to GND...........................................Continuous
Continuous Power Dissipation
16-Pin QSOP (derate 8.3mW/°C above +70°C)......….667mW
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
MAX1761
Small, Dual, High-Efficiency
Buck Controller for Notebooks
ELECTRICAL CHARACTERISTICS (continued)(Circuit of Figure 1, V+ = 15V, CVL= 4.7µF, CREF= 0.1µF, VL not externally driven unless otherwise noted, TA
= 0°C to +85°C, unless
MAX1761
Small, Dual, High-Efficiency
Buck Controller for Notebooks
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, V+ = 15V, CVL= 4.7µF, CREF= 0.1µF, VL not externally driven unless otherwise noted, TA
= -40°C to +85°C,
MAX1761
Small, Dual, High-Efficiency
Buck Controller for Notebooks
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V+ = 15V, CVL= 4.7µF, CREF= 0.1µF, VL not externally driven unless otherwise noted, TA= -40°C to +85°C,
Note 2:If V+ is less than 5V, V+ must be connected to VL. If VL is connected to V+, V+ must be between 4.5V and 5.5V.
Note 3:DC output accuracy specifications refer to the trip-level error of the error amplifier. The output voltage will have a DC regula-
tion higher than the trip level by 50% of the ripple. In PFM mode, the output will rise by approximately 1.5% when transition-
ing from continuous conduction to no load.
Note 4:One-shot times are measured at the DH pin (V+ = 15V, CDH= 400pF, 90% point to 90% point). Actual in-circuit times may
be different due to MOSFET switching speeds.This effect can also cause the switching frequency to vary.
MAX1761
Small, Dual, High-Efficiency
Buck Controller for Notebooks
Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
MAX1761
Small, Dual, High-Efficiency
Buck Controller for Notebooks
Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
MAX1761
Small, Dual, High-Efficiency
Buck Controller for Notebooks
MAX1761
Small, Dual, High-Efficiency
Buck Controller for Notebooks
Typical Application Circuit
The typical application circuit in Figure 1 generates two
low-voltage rails for general-purpose use in notebook
and subnotebook computers (I/O supply, fixed CPU
core supply, DRAM supply). This DC-DC converter
steps down a battery or AC adapter voltage to voltages
from 1.0V to 5.5V with high efficiency and accuracy.
See Table 1 for a list of components for common appli-
cations. Table 2 lists component manufacturers.
Detailed Description
The MAX1761 dual buck controller is designed for low-
voltage power supplies in notebook and subnotebook
computers. Maxim’s proprietary Quick-PWM pulse-
width modulation circuit (Figure 2) is specifically
designed for handling fast load steps while maintaining
a relatively constant operating frequency over a wide
range of input voltages. The Quick-PWM architecture
circumvents the poor load-transient timing problems of
fixed-frequency current-mode PWMs while preventing
problems caused by widely varying switching frequen-
cies in conventional constant-on-time and constant-off-
time PWM schemes.
This MAX1761 controls two synchronously rectified out-
puts with complementary N- and P-channel MOSFETs.
Using the P-channel for the high-side MOSFET elimi-
nates external boost capacitors and diodes, reducing
PC board area and cost. The MAX1761 can step down
input voltages from 5V to 20V, to outputs ranging from
1V to 5.5V on either output. Dual Mode feedback inputs
allow fixed output voltages of 2.5V and 1.8V for OUT1
and OUT2, respectively; or, a resistive voltage-divider
can be used to adjust the output voltages from 1V to
5.5V. Other appropriate applications for this device are
digital cameras, large PDAs, and handy-terminals.
V+ Input and VL +5V Logic Supplies
The MAX1761 has a 5V to 20V input voltage supply
range. A linear regulator powers the control logic and
other internal circuitry from the input supply pin (V+).
The linear regulator’s 4.65V output is available at VL
and can supply 25mA to external circuitry. When used
as an external supply, bypass VL to GND with a 4.7µF
capacitor. VL is turned off when the device is in shut-
down, and drops to approximately 4V when the device
experiences an output voltage fault.
The MAX1761 includes an input undervoltage lockout
(UVLO) circuit that prevents the device from switching
until VL > 4.25V (max). UVLO ensures there is sufficient
drive for the external MOSFETs, prevents the high-side
MOSFET from being turned on for near 100% duty
cycle, and keeps the output in regulation. The UVLO
MAX1761
Small, Dual, High-Efficiency
Buck Controller for Notebooks
comparator has 40mV hysteresis to prevent startup
oscillations on slowly rising input voltages.
If VL is not driven externally, then V+ should be at least
5V to ensure proper operation. If V+ is running from a
5V (±10%) supply, V+ should be externally connected
to VL. Overdriving the VL regulator with an external 5V
supply also increases the MAX1761’s efficiency.
Voltage Reference (REF)
The internal 2V reference is accurate to ±1% (max)
over temperature and can supply a 50µA load current.
Bypass REF to GND with a 0.1µF capacitor when REF
is unloaded. Use a 0.22µF capacitor when applying an
external load.
Free-Running Constant-On-Time PWM
Controller with Input Feed-Forward
The Quick-PWM control architecture is a constant-on-
time, current-mode type with voltage feed-forward
(Figure 3). This architecture relies on the output ripple
voltage to provide the PWM ramp signal. Thus, the out-
put filter capacitor’s ESR acts as a feedback resistor.
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 pro-
portional to output voltage (see the On-Time One-Shot
section). Another one-shot sets a minimum off-time
(400ns typical). 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.
MAX1761
Small, Dual, High-Efficiency
Buck Controller for Notebooks
On-Time One-Shot
The heart of the PWM core is the one-shot that sets the
high-side switch on-time for both controllers. 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 pro-
portional to the battery voltage as measured by the V+
input, and proportional to the output voltage. This algo-
rithm results in a nearly constant switching frequency
despite the absence of a fixed-frequency clock genera-
tor. The benefits of a constant switching frequency are
twofold: first, the switching noise occurs at a known fre-
quency and is easily filtered; second, the inductor rip-
ple current remains relatively constant, resulting in
predictable output voltage ripple and a relatively sim-
ple design procedure. The difference in frequencies
between OUT1 and OUT2 prevents audio-frequency
“beating” and minimizes crosstalk between the two
SMPS. The on-times can be calculated by using the
equation below that references the K values listed in
Table 3.
The 0.1V offset term accounts for the expected drop
across the low-side MOSFET switch.
MAX1761
Small, Dual, High-Efficiency
Buck Controller for Notebooks
The maximum on-time and minimum off-time, tOFF(MIN),
one-shots restrict the continuous-conduction output
voltage. The worst-case dropout performance occurs
with the minimum on-time and the maximum off-time, so
the worst-case duty cycle for VIN= 6V, VOUT1= 5V is
given by:
The duty cycle is ideally determined by the ratio of
input-to-output voltage (Duty Cycle = VOUT/VIN).
Voltage losses in the loop cause the actual duty cycle
to deviate from this relationship. See the Dropout
Performancesection for more information. Equate the
off-time duty cycle restriction to the nonideal input/out-
put voltage duty cycle ratio. Typical units will exhibit
better performance. Operation of any power supply in
dropout will greatly reduce the circuit’s transient
response, and some additional bulk capacitance may
be required to support fast load changes.
Resistive voltage drops in the inductor loop and the
dead-time effect cause switching-frequency variations.
Parasitic voltage losses decrease the effective voltage
applied to the inductor. The MAX1761 compensates by
shifting the duty cycle to maintain the regulated output
voltage. The resulting change in frequency is:
VDROP1is the sum of the parasitic voltage drops in the
inductor discharge path, including synchronous rectifi-
er, inductor, and PC board resistances; VDROP2is the
sum of the resistances in the charging path; and tONis
the on-time calculated by the MAX1761.
In forced PWM mode, the dead-time effect increases
the effective on-time, reducing the switching frequency
as one or both dead times. This occurs only at light or
negative loads when the inductor current reverses.
Under these conditions, the inductor’s EMF causes the
switching node of the inductor to go high during the
dead time, extending the effective on-time.
