MAX1637EEE+-MAX1637EEE+T Fast Delivery |IC PHOENIX CO.,LIMITED

MAX1637EEE+T ,Miniature, Low-Voltage, Precision Step-Down ControllerELECTRICAL CHARACTERISTICS (continued)(Circuit of Figure 1, V = V = 5V, SYNC = V , I = 0mA, T = 0°C ..
MAX1638EAG ,High-Speed Step-Down Controller with Synchronous Rectification for CPU PowerApplicationsPentium Pro™, Pentium II™, PowerPC™, Alpha™,TO VDD MAX1638DHand K6™ SystemsWorkstations ..
MAX1638EAG ,High-Speed Step-Down Controller with Synchronous Rectification for CPU Powerapplications in which' Greater than 90% Efficiency Using N-Channeloutput voltage precision and good ..
MAX1638EAG+ ,High-Speed Step-Down Controller with Synchronous Rectification for CPU PowerELECTRICAL CHARACTERISTICS(V = V = D4 = +5V, PGND = AGND = D0–D3 = 0V, FREQ = REF, T = 0°C to +85°C ..
MAX1638EAG+T ,High-Speed Step-Down Controller with Synchronous Rectification for CPU Powerapplications in which♦ Greater than 90% Efficiency Using N-Channeloutput voltage precision and good ..
MAX1639ESE ,High-Speed Step-Down Controller with Synchronous Rectification for CPU PowerApplicationsLocal DC-DC Converters for CPUsINPUT+5VWorkstationsV VDDCCDesktop ComputersAGND BSTLAN ..
MAX4383ESD ,Ultra-Small / Low-Cost / 210MHz / Single-Supply Op Amps with Rail-to-Rail Outputs and DisableApplicationsOrdering InformationSet-Top BoxesPIN- TOPSurveillance Video SystemsPART TEMP RANGEPACKA ..
MAX4383ESD ,Ultra-Small / Low-Cost / 210MHz / Single-Supply Op Amps with Rail-to-Rail Outputs and Disableapplications). Single +4.5V to +11V OperationThe MAX4380–MAX4384 require only 5.5mA of quies- Rai ..
MAX4383ESD ,Ultra-Small / Low-Cost / 210MHz / Single-Supply Op Amps with Rail-to-Rail Outputs and DisableApplicationsOrdering InformationSet-Top BoxesPIN- TOPSurveillance Video SystemsPART TEMP RANGEPACKA ..
MAX4383ESE ,Ultra-Small / Low-Cost / 210MHz / Single-Supply Op Amps with Rail-to-Rail Outputs and DisableFeaturesThe MAX4380–MAX4384 family of op amps are unity- Low Cost and High Speed:gain-stable devic ..
MAX4383EUD ,Ultra-Small / Low-Cost / 210MHz / Single-Supply Op Amps with Rail-to-Rail Outputs and DisableELECTRICAL CHARACTERISTICS–Single Supply (V = +5V, V = 0, V = V /2, V = V /2, R = ∞ to V /2, DISABL ..
MAX4383EUD+T ,Ultra-Small, Low-Cost, 210MHz, Single-Supply Op Amps with Rail-to-Rail Outputs and DisableELECTRICAL CHARACTERISTICS–Single Supply (V = +5V, V = 0, V = V /2, V = V /2, R = ∞ to V /2, DISABL ..

MAX1637EEE+-MAX1637EEE+T
Miniature, Low-Voltage, Precision Step-Down Controller
General Description
The MAX1637 synchronous, buck, switch-mode power-
supply controller generates the CPU supply voltage in
battery-powered systems. The MAX1637 is a stripped-
down version of the MAX1636 in a smaller 16-pin QSOP
package. The MAX1637 is intended to be powered sep-
arately from the battery by an external bias supply (typi-
cally the +5V system supply) in applications where the
battery exceeds 5.5V. The MAX1637 achieves excellent
DC and AC output voltage accuracy. This device can
operate from a low input voltage (3.15V) and delivers the
excellent load-transient response needed by upcoming
generations of dynamic-clock CPUs.
Using synchronous rectification, the MAX1637 achieves
up to 95% efficiency. Efficiency is greater than 80% over
a 1000:1 load-current range, which extends battery life in
system-suspend or standby mode. Excellent dynamic
response corrects output load transients caused by the
latest dynamic-clock CPUs within five 300kHz clock
cycles. Powerful 1A on-board gate driv-ers ensure fast
external N-channel MOSFET switching.
The MAX1637 features a logic-controlled and synchro-
nizable, fixed-frequency, pulse-width-modulation (PWM)
operating mode. This reduces noise and RF interference
in sensitive mobile-communications and pen-entry appli-
cations. Asserting the SKIPpin enables fixed-frequency
mode, for lowest noise under all load conditions. For a
stand-alone device that includes a +5V VL linear regula-
tor and low-dropout capabilities, refer to the MAX1636
data sheet.
_________________________Applications
Notebook ComputersSubnotebook Computers
Handy-Terminals, PDAs
____________________________Features±2% DC Accuracy0.1% (typ) DC Load Regulation Adjustable Switching Frequency to 350kHzIdle Mode™Pulse-Skipping Operation1.10V to 5.5V Adjustable Output Voltage3.15V Minimum IC Supply Voltage (at VCCpin)Internal Digital Soft-Start1.1V ±2% Reference Output1μA Total Shutdown Current Output Overvoltage Crowbar ProtectionOutput Undervoltage Shutdown (foldback)Tiny 16-Pin QSOP Package
MAX1637
Miniature, Low-Voltage,
Precision Step-Down Controller
CSHSKIP
BST
PGND
VGG
VCC
TOP VIEW
MAX1637
QSOP
CSL
SHDN
REF
SYNC
GND
A "+" SIGN WILL REPLACE THE FIRST PIN INDICATOR ON LEAD-FREE PACKAGES.
__________________Pin Configuration
__________Typical Operating Circuit
19-1321; Rev 2; 8/05
EVALUATION KIT
AVAILABLE
______________Ordering Information
Idle Mode is a trademark of Maxim Integrated Products.
MAX1637
SHDN
GND
VBATTVBIAS
PGND
VCCVGG
BST
CSH
CSL
SKIP
SYNC
REF
OUTPUT
+Denotes lead-free package.
PARTTEMP RANGEPIN-PACKAGE
MAX1637EEE40°C to +85°C16 QSOP
MAX1637EEE+40°C to +85°C16 QSOP
MAX1637
Miniature, Low-Voltage,
Precision Step-Down Controller
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, VCC= VGG= 5V, SYNC = VCC, IREF= 0mA, TA= 0°C to +85°C, unless otherwise noted. Typical values are at = +25°C.)
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.
GND to PGND.............................................................+2V to -2V
LX, BST to GND......................................................-0.3V to +36V
BST, DH to LX...........................................................-0.3V to +6V
VCC, VGG, CSL, CSH, SHDNto GND.......................-0.3V to +6V
DL to GND..................................................-0.3V to (VGG+ 0.3V)
REF, SKIP, SYNC, CC to GND...................-0.3V to (VCC+ 0.3V)
REF Output Current.............................................................20mA
REF Short-Circuit to GND..............................................Indefinite
Operating Temperature Range...........................-40°C to +85°C
Continuous Power Dissipation (TA= +70°C)
QSOP (derate 8.3mW/°C above +70°C)......................667mW
Storage Temperature Range.............................-65°C to +160°C
Junction Temperature......................................................+150°C
Lead Temperature (soldering, 10s).................................+300°C
SYNC = GND
SYNC = VCC
FB tied to VOUT, 0mV < (CSH - CSL) < 80mV,
includes line and load regulation
VCC= 3.15V to 5.5V
REF load = 0µA to 50µA
VCC, VGG
REF load = 0µA
Rising edge, hysteresis = 15mV
Rising edge, hysteresis = 15mV
SHDN= GND, VCC= VGG
CSH - CSL = 0mV to CSH - CSL = 100mV
CSH - CSL
VCC= 5V
VCC= 3.3V
SHDNto full current limit, four levels
VFB= VREF
CONDITIONS
170200230Oscillator FrequencykHz2703003303REF Line Regulation10REF Load Regulation1.0801.1001.120REF Output Voltage2.803.05VGGUndervoltage Lockout Threshold2.803.05VCCUndervoltage Lockout Threshold2AC Load Regulation203040Idle-Mode Switchover Threshold
clocks512Soft-Start Ramp Time-5050FB Input Current3.155.5Input Voltage Range0.53Shutdown Supply Current1.0801.1001.120Output Voltage
VREF5.5Output Adjustment RangeVVREF3.6
UNITSMINTYPMAXPARAMETER
CSH > CSL
CSH < CSL100120Current-Limit ThresholdmV-145-100-55
Output not switching1.52.5Power ConsumptionmW11.75
SYNC = GND
SYNC = VCC200SYNC Input Pulse Width High939692Maximum Duty Factor
(Note 1)
kHz240340SYNC Input Frequency Range200SYNC Input Rise/Fall Time200SYNC Input Pulse Width Low
VCC= VGG= 5V
VCC= VGG= 3.3V
SMPS CONTROLLER
INTERNAL REFERENCE
OSCILLATOR
MAX1637
Miniature, Low-Voltage,
Precision Step-Down Controller
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, VCC= VGG= 5V, SYNC = VCC, IREF= 0mA, TA= 0°C to +85°C, unless otherwise noted. Typical values are at = +25°C.)
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, VCC= VGG= 5V, SYNC = VCC, IREF= 0mA, TA= -40°C to +85°C, unless otherwise noted.) (Note 2)
High or low, DH or DL
DH or DL forced to 2V
CSH = CSL = 5V, VCC= VGG= GND,
either CSH or CSL input
FB to DL delay, 22mV overdrive, CGATE= 2000pF
FB, with respect to regulation point
From shutdown or power-on-reset state
Pin at GND or VCC
SHDN,SKIP, SYNC
% of nominal output
SHDN,SKIP, SYNC
CONDITIONS7Gate Driver On-Resistance1Gate Driver Sink/Source Current10Current-Sense Input Leakage Current-11Logic Input Bias Current0.8Logic Input Voltage Low2.4Logic Input Voltage High1.25Overvoltage Fault Propagation Delay4710Overvoltage Trip Threshold
clocks6144Output Undervoltage Lockout Delay607080Output Undervoltage Lockout Threshold
UNITSMINTYPMAXPARAMETER
FB tied to VOUT, 0mV < (CSH - CSL) < 80mV,
includes line and load regulation
SYNC = GND
VCC, VGG
SYNC = VCC
Rising edge, hysteresis = 15mV
Rising edge, hysteresis = 15mV
VCC= 3.3V
VCC= VGG= 3.3V, output not switching
VCC= 5V
VCC= VGG= 5V, output not switching
CSH > CSL
CONDITIONS
kHz240340SYNC Input Frequency Range200SYNC Input Rise/Fall Time200SYNC Input Pulse Width Low200SYNC Input Pulse Width High
kHz170230Oscillator Frequency2623382.803.05VGGUndervoltage Lockout Threshold2.803.05VCCUndervoltage Lockout Threshold1.75Power ConsumptionmW2.570130Current-Limit Threshold1.0801.120Output Voltage3.155.5Input Voltage Range
VREF3.6Output Adjustment RangeVVREF5.5
UNITSMINTYPMAXPARAMETER
OVERVOLTAGE PROTECTION
INPUTS AND OUTPUTS
SMPS CONTROLLER
INTERNAL REFERENCE
OSCILLATOR
41256879SUPPLY CURRENT
vs. LOAD CURRENT
MAX1637-07
LOAD CURRENT (A)
+ V
SUPPLY CURRENT (mA)
SYNC = HIGH
SYNC = LOW
SKIP = LOW
MAX1637
Miniature, Low-Voltage,
Precision Step-Down Controller
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, VCC= VGG= 5V, SYNC = VCC, IREF= 0mA, TA= -40°C to +85°C, unless otherwise noted.) (Note 2)
SHDN,SKIP, SYNC
SHDN,SKIP, SYNC
% of nominal output
FB, with respect to regulation point
CONDITIONS0.8Logic Input Voltage Low2.4Logic Input Voltage High6080Output Undervoltage Lockout Threshold4.010Overvoltage Trip Threshold
UNITSMINTYPMAXPARAMETER
Note 1:Guaranteed by design, not production tested.
Note 2:Specifications from -40°C to 0°C are guaranteed by design and not production tested.
__________________________________________Typical Operating Characteristics
(VOUT= 3.3V, TA = +25°C, unless otherwise noted.)
EFFICIENCY vs. LOAD CURRENT
(1.7V/7A CIRCUIT)
MAX1637-01
LOAD CURRENT (A)
EFFICIENCY (%)
SKIP = LOW
VBATT = 7V
VBATT = 15VVBATT = 22V
EFFICIENCY vs. LOAD CURRENT
(2.5V/3A CIRCUIT)
MAX1637-02
LOAD CURRENT (A)
EFFICIENCY (%)
VBATT = 15V
SKIP = LOW
VBATT = 7V
VBATT = 22V
EFFICIENCY vs. LOAD CURRENT
(2.5V/2A CIRCUIT)
MAX1637-03
LOAD CURRENT (A)
EFFICIENCY (%)
VBATT = 7V
SKIP = LOW
VBATT = 15VVBATT = 22V
EFFICIENCY vs. LOAD CURRENT
(3.3V/3A CIRCUIT)
MAX1637-04
LOAD CURRENT (A)
EFFICIENCY (%)
VBATT = 5V
VBATT = 30V
VBATT = 15V
SKIP = LOW
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX1637-06
SUPPLY VOLTAGE (V)
+ V
SUPPLY CURRENT (mA)
ILOAD = 1A
VOUT = 3.3V
SKIP = HIGH
SKIP = LOW
OVERVOLTAGE PROTECTION
INPUTS AND OUTPUTS
MAX1637
Miniature, Low-Voltage,
Precision Step-Down Controller
LOAD REGULATION
vs. LOAD CURRENT
MAX1637-08
LOAD CURRENT (A)
LOAD REGULATION
OUT
(mV)
REF LOAD-REGULATION ERROR
vs. REF LOAD CURRENT
MAX1637-09
REF LOAD CURRENT (μA)
REF LOAD REGULATION
V (mV)
DROPOUT VOLTAGE
vs. LOAD CURRENT
MAX1637-10
LOAD CURRENT (A)
DROPOUT VOLTAGE (mV)
VOUT FORCED TO 3.27V
SYNC = VCC
VOUT
20mV/div
VLX
INDUCTOR
CURRENT
1A
0V
SWITCHING WAVEFORMS
(PWM MODE)
MAX1637-13
1μs/div
VOUT
50mV/div
LOAD
CURRENT
LOAD-TRANSIENT RESPONSE
(3.3V/3A, PWM MODE)
MAX1637 TOC11
100μs/div
VOUT
50mV/div
5A LOAD CURRENT
10A
LOAD-TRANSIENT RESPONSE
(1.8V, PWM MODE)
MAX1637 TOC12
100μs/div
VOUT
50mV/div
VLX
INDUCTOR
CURRENT
1A
SWITCHING WAVEFORMS
(PFM MODE)
MAX1637-14
20μs/div
VOUT = 1.7V
1μs/div
SWITCHING WAVEFORMS
DROPOUT OPERATION
MAX1637-15
VOUT
10mV/div
VLX
2V/div
INDUCTOR
CURRENT
1A
VOUT FORCED TO 3.27V
SYNC = VCC
____________________________________Typical Operating Characteristics (continued)
(VOUT= 3.3V, TA = +25°C, unless otherwise noted.)
MAX1637
Miniature, Low-Voltage,
Precision Step-Down Controller
____________________________________Typical Operating Characteristics (continued)
(VOUT= 3.3V, TA = +25°C, unless otherwise noted.)
500μs/div
TIME EXITING SHUTDOWN
(VOUT = 3.3V, ILOAD = 7A)
MAX1637-16
VOUT
1V/div
VSHDN
5V/div
VOUT
100mV/div
VDL
INDUCTOR
CURRENT-5A
0A
0V
5V
-10A
OVERVOLTAGE-PROTECTION WAVEFORMS
(VIN SHORTED TO VOUT
THROUGH A 0.5Ω RESISTOR)
MAX1637-17
10μs/div
______________________________________________________________Pin Description
PIN
High-Side Current-Sense InputCSH1
FUNCTIONNAME
Low-Side Current-Sense InputCSL2
Compensation Pin. Connect a small capacitor to GND to set the integration time constant.CC4
Feedback Input. Connect to center of resistor divider.FB3
Shutdown Control Input. Turns off entire IC. When low, reduces supply current below 0.5µA (typ). Drive with
logic input or connect to RC network between GND and VCCfor automatic start-up.SHDN6
Analog GroundGND8
Oscillator Frequency Select and Synchronization Input. Tie to VCCfor 300kHz operation; tie to GND for
200kHz operation.SYNC7
1.100V Reference Output. Capable of sourcing 50µA for external loads. Bypass with 0.22µF minimum.REF5
Gate-Drive and Boost-Circuit Power Supply. Can be driven from a supply other than VCC. If the same supply
is used by both VCCand VGG, isolate VCCfrom VGGwith a 20Ωresistor. Bypass to PGND with a 4.7µF
capacitor. VGGcurrent = (QG1+ QG2) x f, where QGis the MOSFET gate charge at VGS= VGG.
VGG10
Power GroundPGND12
Low-Side Gate-Driver OutputDL11
High-Side Gate-Driver OutputDH14
Low-Noise Mode Control. Forces fixed-frequency PWM operation when high.SKIP16
Inductor ConnectionLX15
Boost Capacitor ConnectionBST13
Main Analog Supply-Voltage Input to the Chip. VCCpowers the PWM controller, logic, and reference. Input
range is 3.15V to 5.5V. Bypass to GND with a 0.1µF capacitor close to the pin.VCC9
MAX1637
Miniature, Low-Voltage,
Precision Step-Down Controller
MAX1637
0.1μF
VBIAS
+5V
NOMINAL
0.1μF
1μF
470pF
CMPSH-3C2
OUTPUT
4.7μF
*SEE RECTIFIER CLAMP DIODE SECTION
**OPTIONAL RC NETWORK FOR POWER-ON-RESET
PGND
BST
VGG
VCC
VBATT
CSH
CSL
1M**
ON/OFF
GND
SHDN
REF
SYNC
20Ω
SKIP
0.01μF**
Figure 1. Standard Application Circuit
______Standard Application Circuit
The basic MAX1637 buck converter (Figure 1) is easily
adapted to meet a wide range of applications where a
5V or lower supply is available. The components listed
in Table 1 represent a good set of trade-offs among
cost, size, and efficiency, while staying within the worst-
case specification limits for stress-related parameters
such as capacitor ripple current. Do not change the cir-
cuit’s switching frequency without first recalculating
component values (particularly inductance value at
maximum battery voltage).
The power Schottky diode across the synchronous rec-
tifier is optional because the MOSFETs chosen incorpo-
rate a high-speed silicon diode. However, installing the
Schottky will generally improve efficiency by about 1%.
If used, the Schottky diode DC current must be rated to
at least one-third of the maximum load current.
_______________Detailed Description
The MAX1637 is a BiCMOS, switch-mode power-supply
(SMPS) controller designed primarily for buck-topology
regulators in battery-powered applications where high
efficiency and low quiescent supply current are critical.
Light-load efficiency is enhanced by automatic idle-
mode operation—a variable-frequency, pulse-skipping
mode that reduces transition and gate-charge losses.
The step-down, power-switching circuit consists of two
N-channel MOSFETs, a rectifier, and an LC output filter.
Output voltage for this device is the average AC volt-
age at the switching node, which is regulated by
changing the duty cycle of the MOSFET switches. The
gate-drive signal to the high-side N-channel MOSFET,
which must exceed the battery voltage, is provided by
a flying-capacitor boost circuit that uses a 100nF
capacitor between BST and LX. Figure 2 shows the
major circuit blocks.
LOAD CURRENT
MAX1637
Miniature, Low-Voltage,
Precision Step-Down Controller
Table 1. Component Selection for Standard Applications
Table 2. Component Suppliers
2.5VOutput Voltage Range
300kHzFrequency
Chipset SupplyApplication
1/2 Si4902DY or
1/2 MMDF3NO3HD
Q1 High-Side
MOSFET
7V to 22VInput Voltage Range
(619) 661-6835(81) 7-2070-1174Sanyo
Tokin(408) 432-8020
(847) 390-4373
(1) 408-434-0375
(1) 847-390-4428TDK
Sprague
(847) 956-0666(81) 3-3607-5144Sumida
(603) 224-1961
(714) 373-7939
(408) 988-8000
(1) 714-373-7183Panasonic
(1) 603-224-1430
(1) 408-970-3950Siliconix
(602) 303-5454(1) 602-994-6430Motorola
(847) 696-2000
COMPANY
Matsuo(714) 969-2491(1) 714-960-6492
USA PHONEFACTORY FAX
(COUNTRY CODE)
(1) 847-696-9278Marcon/United
Chemi-Con
COMPANY
Central
Semiconductor
Fairchild(408) 721-2181(1) 408-721-1635
(512) 992-7900(1) 512-992-3377IRC
Dale
(310) 322-3331(1) 310-322-3332International
Rectifier (IR)
(605) 668-4131
(847) 639-6400
(561) 241-7876
(1) 847-639-1469Coilcraft
(1) 605-665-1627
(1) 561-241-9339Coiltronics
USA PHONE
(516) 435-1110
(803) 946-0690
FACTORY FAX
(COUNTRY CODE)
(1) 516-435-1824
(1) 803-626-3123AVX
2.5V
300kHz
Chipset Supply
International Rectifier
IRF7403 or
Siliconix Si4412
7V to 22V
3.3V1.7V
300kHz300kHz
General PurposeCPU Core
International Rectifier
IRF7403 or
Siliconix Si4412
Fairchild FDS9412 or
International Rectifier
IRF7403
4.75V to 30V7V to 22V
10µF, 25V ceramic
Tokin C34Y5U1E106Z
or Marcon/United
Chemicon
THCR40E1E106ZT
10µF, 25V ceramic
Tokin C34Y5U1E106Z
or Marcon/United
Chemicon
THCR40E1E106ZT
C1 Input Capacitor
0.020Ω, 1% (2010)
Dale WSL-2010-R020F
0.033Ω, 1% (2010)
Dale WSL-2010-R033FR1 Resistor
470µF, 6.3V tantalum
Kemet
T510X477(1)006AS or
470µF, 4V tantalum
Sprague
594D477X0004R2T
220µF, 6.3V tantalum
Sprague
595D227X96R3C2
C2 Output Capacitor
10µH
Sumida CDRH125-100
10µH
Coilcraft
DO3316P-103 or
Coiltronics UP2-100
L1 Inductor
International Rectifier
IRF7413 or
Siliconix Si4410DY
1/2 Si4902DY or
1/2 MMDF3NO3HDQ2 Low-Side MOSFET
10µF, 30V
Sanyo OS-CON
4 x 10µF, 25V ceramic
Tokin C34Y5U1E106Z
or Marcon/United
Chemicon
THCR40E1E106ZT
0.020Ω, 1% (2010)
Dale WSL-2010-R020F
0.010Ω, 1% (2512)
Dale WSL-2512-R010F
470µF, 6.3V tantalum
Kemet
T510X477(1)006AS or
470µF, 4V tantalum
Sprague
594D477X0004R2T
3 x 470µF, 6.3V tantalum
Kemet
T510X477(1)006AS or
470µF, 4V tantalum
Sprague
594D477X0004R2T
10µH Sumida
CDRH125-100
2.2µH
Panasonic P1F2R0HL or
Coiltronics UP4-2R2 or
Coilcraft
DO5022P-222HC
International Rectifier
IRF7413 or
Siliconix Si4410DY
Fairchild FDS6680 or
Siliconix Si4420DY
COMPONENT3A (EV KIT)2A3A7A (EV KIT)
LOAD CURRENT
MAX1637
Miniature, Low-Voltage,
Precision Step-Down Controller
The pulse-width-modulation (PWM) controller consists
of a multi-input PWM comparator, high-side and low-
side gate drivers, and logic. It uses a 200kHz/300kHz
synchronizable oscillator. The MAX1637 contains fault-
protection circuits that monitor the PWM output for
undervoltage and overvoltage. It includes a 1.100V pre-
cision reference. The circuit blocks are powered from
an internal IC power rail that receives power from VCC.
VGGprovides direct power to the synchronous-switch
gate driver, but provides indirect power to the high-
side-switch gate driver via an external diode-capacitor
boost circuit.
REF
POWER
200kHz
300kHz
OSCPWM
LOGIC
3.15V TO 5.5V
VBATT
VOUT
REF
SHDN
SYNCVCC
DL
PGND
BST
VGG
SKIP
CSH
CSL
FB
REF
GND
VREF +7%
VREF -30%
60kHz
LP FILTER
SHUTDOWN
CONTROL
1.1V
REF.
ERROR
INTEGRATOR+
MAX1637
OVERVOLTAGE
FAULT
UNDER-
VOLTAGE
FAULT
OFF
SLOPE
COMPENSATION
VBIAS
Figure 2. Functional Diagram
MAX1637
Miniature, Low-Voltage,
Precision Step-Down Controller
PWM Controller Block
The heart of the current-mode PWM controller is a
multi-input, open-loop comparator that sums four sig-
nals: the output voltage error signal with respect to
the reference voltage, the current-sense signal, the
integrated voltage-feedback signal, and the slope-
compensation ramp (Figure 3). The PWM controller is
a direct-summing type, lacking a traditional error
amplifier and the phase shift associated with it. This
direct-summing configuration approaches ideal
cycle-by-cycle control over the output voltage.
SHOOT-
THROUGH
CONTROL
30mV
LEVEL
SHIFT
OSC
LEVEL
SHIFT
REF
CURRENT
LIMIT
SYNCHRONOUS
RECTIFIER CONTROL
SHDN
-100mV
CSH
CSL
REF
BST
VGG
PGND
SLOPE
COMPENSATION
SKIP
COUNTER
DAC
SOFT-START
Figure 3. PWM Controller Functional Diagram

Partno	Mfg	Dc	Qty	Available	Descript
MAX1637EEE+	MAXIM	N/a	10	avai	Miniature, Low-Voltage, Precision Step-Down Controller
MAX1637EEE+T	MAXIM	N/a	30000	avai	Miniature, Low-Voltage, Precision Step-Down Controller