MAX1655EEE+ ,High-Efficiency, PWM, Step-Down DC-DC Controllers in 16-Pin QSOPApplicationsFEEDBACK SPECIALPART COMPATIBILITYNotebook ComputersVOLTAGE (V) FEATUREPDAsRegulates po ..
MAX1655EEE+ ,High-Efficiency, PWM, Step-Down DC-DC Controllers in 16-Pin QSOPFeaturesThe MAX1652–MAX1655 are high-efficiency, pulse- ♦ 96% Efficiencywidth-modulated (PWM), step ..
MAX1655EEE+T ,High-Efficiency, PWM, Step-Down DC-DC Controllers in 16-Pin QSOPFeaturesThe MAX1652–MAX1655 are high-efficiency, pulse- ♦ 96% Efficiencywidth-modulated (PWM), step ..
MAX1655ESE ,High-Efficiency / PWM / Step-Down DC-DC Controllers in 16-Pin QSOPFeaturesThe MAX1652–MAX1655 are high-efficiency, pulse- ' 96% Efficiencywidth-modulated (PWM), step ..
MAX1655ESE+ ,High-Efficiency, PWM, Step-Down DC-DC Controllers in 16-Pin QSOPGeneral Description ________
MAX1658ESA ,350mA / 16.5V Input / Low-Dropout Linear RegulatorsELECTRICAL CHARACTERISTICS(V = 5V (MAX1658), V = 6V (MAX1659); C = 10µF; SHDN = IN; T = T to T ; un ..
MAX4412EXK+T ,Low-Cost, Low-Power, Ultra-Small, 3V/5V, 500MHz Single-Supply Op Amps with Rail-to-Rail OutputsFeaturesThe MAX4412 single and MAX4413 dual operational♦ Ultra-Low 1.7mA Supply Currentamplifiers a ..
MAX4412EXK+TG21 ,Low-Cost, Low-Power, Ultra-Small, 3V/5V, 500MHz Single-Supply Op Amps with Rail-to-Rail OutputsApplicationsT = Tape and reel.Pin ConfigurationsTypical Operating CharacteristicSUPPLY CURRENT vs. ..
MAX4412EXK-T ,Low-Cost, Low-Power, Ultra-Small, 3V/5V, 500MHz Single-Supply Op Amps with Rail-to-Rail OutputsApplicationsRail-to-Rail is a registered trademark of Nippon Motorola, Ltd.Typical Operating Charac ..
MAX4413EKA+T ,Low-Cost, Low-Power, Ultra-Small, 3V/5V, 500MHz Single-Supply Op Amps with Rail-to-Rail OutputsELECTRICAL CHARACTERISTICS(V = +2.7V to +5.5V, V = V /2 - 0.75V, V = 0, R = ∞ to V /2, V = V /2, T ..
MAX4414ESA ,Low-Power, +3V/+5V, 400MHz Single-Supply Op Amps with Rail-to-Rail OutputsApplicationsTypical Operating Characteristic_Selector GuideSUPPLY CURRENT vs. SUPPLY VOLTAGE (PER A ..
MAX4416ESA ,Low-Power, +3V/+5V, 400MHz Single-Supply Op Amps with Rail-to-Rail OutputsFeaturesThe MAX4414–MAX4419 operational amplifiers com- Ultra-Low 1.6mA Supply Currentbine high-sp ..
MAX1652EEE+-MAX1653EEE+-MAX1653EEE+T-MAX1653ESE+-MAX1655EEE+-MAX1655EEE+T-MAX1655ESE+
High-Efficiency, PWM, Step-Down DC-DC Controllers in 16-Pin QSOP
General DescriptionThe MAX1652–MAX1655 are high-efficiency, pulse-
width-modulated (PWM), step-down DC-DC controllers
in small QSOP packages. The MAX1653/MAX1655 also
come in 16-pin narrow SO packages that are pin-
compatible upgrades to the popular MAX797. Improve-
ments include higher duty-cycle operation for better
dropout, lower quiescent supply currents for better
light-load efficiency, and an output voltage down to 1V
(MAX1655).
The MAX1652–MAX1655 achieve up to 96% efficiency
and deliver up to 10A using a unique Idle Mode™ syn-
chronous-rectified PWM control scheme. These devices
automatically switch between PWM operation at heavy
loads and pulse-frequency-modulated (PFM) operation
at light loads to optimize efficiency over the entire out-
put current range. The MAX1653/MAX1655 also feature
logic-controlled, forced PWM operation for noise-sensi-
tive applications.
All devices operate with a selectable 150kHz/300kHz
switching frequency, which can also be synchronized
to an external clock signal. Both external power switch-
es are inexpensive N-channel MOSFETs, which provide
low resistance while saving space and reducing cost.
The MAX1652 and MAX1654 have an additional feed-
back pin that permits regulation of a low-cost second
output tapped from a transformer winding. The
MAX1652 provides an additional positive output. The
MAX1654 provides an additional negative output.
The MAX1652–MAX1655 have a 4.5V to 30V input volt-
age range. The MAX1652/MAX1653/MAX1654’s output
range is 2.5V to 5.5V while the MAX1655’s output range
extends down to 1V. An evaluation kit (MAX1653EVKIT)
is available to speed designs.
ApplicationsNotebook Computers
PDAs
Cellular Phones
Hand-Held Computers
Handy-Terminals
Mobile Communicators
Distributed Power
____________________________Features96% EfficiencySmall, 16-Pin QSOP Package
(half the size of a 16-pin narrow SO)Pin-Compatible with MAX797 (MAX1653/MAX1655)Output Voltage Down to 1V (MAX1655)4.5V to 30V Input Range99% Duty Cycle for Lower Dropout170μA Quiescent Supply Current3μA Logic-Controlled ShutdownDual, N-Channel, Synchronous-Rectified ControlFixed 150kHz/300kHz PWM Switching,
or Synchronized from 190kHz to 340kHzProgrammable Soft StartLow-Cost Secondary Outputs (MAX1652/MAX1654)igh-Efficiency, PWM, Step-Down
DC-DC Controllers in 16-Pin QSOP19-1357; Rev 1; 7/98
EVALUATION KITAVAILABLE
Ordering Informationlection Guide
Pin Configurations appear at end of data sheet.Idle Mode is a trademark of Maxim Integrated Products.
PARTFEEDBACK
VOLTAGE (V)
SPECIAL
FEATURECOMPATIBILITYMAX16522.5
Regulates positive
secondary voltage
(such as +12V)
Same pin order
as MAX796, but
smaller package
MAX16532.5Logic-controlled,
low-noise mode
Pin-compatible
with MAX797
MAX16542.5
Regulates negative
secondary voltage
(such as -5V)
Same pin order
as MAX799, but
smaller package
MAX16551
Low output volt-
ages (1V to 5.5V);
logic-controlled,
low-noise mode
Pin compatible
with MAX797
(except for feed-
back voltage)
PART
MAX1652EEE-40°C to +85°C
TEMP. RANGEPIN-PACKAGE16 QSOP
MAX1653EEE-40°C to +85°C16 QSOP
MAX1654EEE-40°C to +85°C16 QSOP
MAX1653ESE-40°C to +85°C16 Narrow SO
MAX1655ESE-40°C to +85°C16 Narrow SO
MAX1655EEE-40°C to +85°C16 QSOP
igh-Efficiency, PWM, Step-Down DC-DC Controllers in 16-Pin QSOP
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS(V+ = +15V, GND = PGND = 0V, SYNC = REF, IVL= IREF= 0A, 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 +36V
GND to PGND.......................................................-0.3V to +0.3V
VL to GND................................................................-0.3V to +6V
BST to GND............................................................-0.3V to +36V
DH to LX.....................................................-0.3V to (BST + 0.3V)
LX to BST..................................................................-6V to +0.3V
SHDNto GND...............................................-0.3V to (V+ + 0.3V)
SYNC, SS, REF, SECFB, SKIP,FB to GND...-0.3V to (VL + 0.3V)
DL to PGND..................................................-0.3V to (VL + 0.3V)
CSH, CSL to GND....................................................-0.3V to +6V
VL Short Circuit to GND..............................................Momentary
REF Short Circuit to GND...........................................Continuous
VL Output Current...............................................+50mA to -1mA
REF Output Current...............................................+5mA to -1mA
Continuous Power Dissipation (TA= +70°C)
SO (derate 8.70mW/°C above +70°C) .......................696mW
QSOP (derate 8.3mW/°C above +70°C) ....................667mW
Operating Temperature Range
MAX165_E_E ..................................................-40°C to +85°C
Storage Temperature Range.............................-65°C to +160°C
Lead Temperature (soldering, 10sec).............................+300°C
Rising edge, falling edge hysteresis = 60mV
Rising edge, falling edge hysteresis = 50mV
SHDN= 2V, 0 < IVL< 25mA, 5.5V < V+ < 30V
Rising edge, falling edge, hysteresis = 22mV (MAX1654)
CSH - CSL, negative
CSH - CSL, positive
Falling edge, rising edge, hysteresis = 22mV (MAX1652)
6V < V+ < 30V
25mV < (CSH - CSL) < 80mV
0 < (CSH - CSL) < 80mV, FB = VL, 6V < V+ < 30V,
includes line and load regulation
External resistor divider
VSS= 4V
0 < (CSH - CSL) < 80mV
VSS= 0V
CONDITIONS4.24.54.7VL/CSL Switchover Voltage3.83.94.0VL Fault Lockout Voltage4.75.05.3VL Output Voltage
-0.0500.05V2.452.502.55SECFB Regulation Setpoint2.0SS Fault Sink Current2.54.06.5SS Source Current4.530Input Supply Range
-50-100-160mV80100120Current-Limit Voltage
%/V0.030.06Line Regulation
1.24.855.065.255V Output Voltage (CSL)5.5
Nominal Adjustable Output
Voltage Range2Load Regulation
UNITSMINTYPMAXPARAMETER0 < (CSH - CSL) < 80mV, FB = 0V, 4.5V < V+ < 30V,
includes line and load regulation V3.203.343.463.3V Output Voltage (CSL)
MAX1655
MAX1652/MAX1653/
MAX1654
2.432.502.57MAX1652/MAX1653/
MAX1654
CSH - CSL = 0V, CSL = FB,
SKIP= 0V, 4.5V < V+ < 30V
MAX1655
Feedback Voltage
3.3V AND 5V STEP-DOWN CONTROLLERS
FLYBACK/PWM CONTROLLER
INTERNAL REGULATOR AND REFERENCE
igh-Efficiency, PWM, Step-DowDC-DC Controllers in 16-Pin QSOP
Note 1:Since the reference uses VL as its supply, V+ line-regulation error is insignificant.
Note 2:At very low input voltages, quiescent supply current may increase due to excessive PNP base current in the VL linear
regulator. This occurs if V+ falls below the preset VL regulation point (5V nominal).
ELECTRICAL CHARACTERISTICS (continued)(V+ = +15V, GND = PGND = 0V, SYNC = REF, IVL= IREF= 0A, TA
= 0°C to +85°C,unless otherwise noted.)
SECFB, 0 or 4V
SHDN, 0 or 30V
SHDN, SKIP
SYNC
SYNC = 0 or 5V
SYNC = REF
Guaranteed by design, not tested
CSH = CSL = 5.5V
V+ = 4.5V, CSH = CSL = 4.0V (Note 2)
SYNC = 0 or 5V
Falling edge
0 < IREF< 100μA
SYNC = REF
SHDN= 0V, CSL = 5.5V, CSH = 5.5V, V+ = 0 or 30V,
VL = 0V
CONDITIONSNo external load (Note 1)
Input Current
2.0VVL - 0.5Input High Voltage989998Dropout-Mode Maximum Duty
Cycle
kHz190340Oscillator Sync Range200SYNC Rise/Fall Time200SYNC Low Pulse Width200SYNC High Pulse Width
125150175kHz270300330Oscillator Frequency
2.462.502.542Quiescent Power Consumption8Dropout Power Consumption15
V+ Shutdown Current2.02.4Reference Fault Lockout Voltage15Reference Load Regulation0.11CSL, CSH Shutdown Leakage
Current
UNITSMINTYPMAXPARAMETERSHDN= 0V, V+ = 30V, CSL = 0 or 5.5V
FB = CSH = CSL = 5.5V, VL switched over to CSLV+ Off-State Leakage Current
DL forced to 2V
FB, FB = REF
CSH, CSL, CSH = CSL ≤4V
SYNC, SKIP1DL Sink/Source Current
±0.1
SHDN, SKIP
SYNC
0.5V0.8Input Low Voltage
DH forced to 2V, BST - LX = 4.5VA1DH Sink/Source Current
High or low, BST - LX = 4.5V
High or low1.55DH On-Resistance1.55DL On-Resistance
Reference Output VoltageV
OSCILLATOR AND INPUTS/OUTPUTS715
igh-Efficiency, PWM, Step-Down DC-DC Controllers in 16-Pin QSOP
ELECTRICAL CHARACTERISTICS (continued)(V+ = +15V, GND = PGND = 0V, SYNC = REF, IVL= IREF= 0A, TA
= -40°C to +85°C,unless otherwise noted.) (Note 3)
Note 3:Specifications from 0°C to -40°C are guaranteed by design, not production tested.
0 < (CSH - CSL) < 70mV, FB = VL, 4.5V < V+ < 30V,
includes line and load regulation
0 < (CSH - CSL) < 70mV, FB = VL, 6V < V+ < 30V,
includes line and load regulation
CONDITIONS3.163.503.3V Output Voltage (CSL)4.530Input Supply Range4.805.305V Output Voltage (CSL)
UNITSMINTYPMAXPARAMETERCSH - CSL, negative
CSH - CSL, positive
-40-160Current-Limit Voltage
Feedback Voltage2.402.6070130
FB = CSH = CSL = 5.5V, VL switched over to CSL
SHDN= 0V, V+ = 30V, CSL = 0 or 5.5V
Rising edge, hysteresis = 60mV
No external load (Note 1)
0 < IREF< 100μA15V+ Off-State Leakage Current10V+ Shutdown Current
Rising edge, hysteresis = 50mV
SHDN= 2V, 0 < IVL< 25mA, 5.5V < V+ < 30V
4.24.7VL/CSL Switchover Voltage2.432.57Reference Output Voltage
Falling edge, hysteresis = 22mV (MAX1652)
Falling edge, hysteresis = 22mV (MAX1654)15Reference Load Regulation3.754.05VL Fault Lockout Voltage4.75.3VL Output Voltage
2.402.60V-0.080.08SECFB Regulation Setpoint
SYNC = REF
SYNC = 0 or 5V
kHz210320Oscillator Sync Range
kHzSYNC = REF
120180Oscillator Frequency250SYNC High Pulse Width250SYNC Low Pulse Width
2503502Quiescent Power Consumption
High or low, BST - LX = 4.5V
High or low
SYNC = 0 or 5V5DH On-Resistance5DL On-Resistance98Maximum Duty Cycle
CSH - CSL = 0V, 5V < V+ < 30V,
CSL = FB, SKIP= 0V
6V < V+ < 30V%/V0.06Line Regulation
3.3V and 5V STEP-DOWN CONTROLLERS
FLYBACK/PWM CONTROLLER
INTERNAL REGULATOR AND REFERENCE
OSCILLATOR AND INPUTS/OUTPUTSMAX1652/MAX1653/
MAX1654
MAX1655
igh-Efficiency, PWM, Step-DowDC-DC Controllers in 16-Pin QSOPSHDN
+12V
OUTPUT
+5V
OUTPUT
INPUT
6V TO 30V
BST
PGND
CSH
CSL
REF
SYNC
GND
SECFB
MAX1652
MAX1653
MAX1655
SHDN
+3.3V
OUTPUT
INPUT
4.5V TO 30V
BST
PGND
CSH
CSL
REF
SYNC
GND
SKIPFBVL
Typical Operating Circuits
__________________________________________Typical Operating Characteristics(Circuit of Figure 1, SKIP= GND, TA = +25°C, unless otherwise noted.)
EFFICIENCY vs.
LOAD CURRENT (3.3V/1A CIRCUIT)
1652 toc01
LOAD CURRENT (A)
(%
V+ = 6V
MAX1653
f = 300kHz
V+ = 28V
V+ = 12V
EFFICIENCY vs.
LOAD CURRENT (3.3V/2A CIRCUIT)
AX1652 toc02
LOAD CURRENT (A)
(%V+ = 6V
V+ = 28V
V+ = 12V
MAX1653
f = 300kHz
EFFICIENCY vs.
LOAD CURRENT (3.3V/3A CIRCUIT)
AX1652 toc03
LOAD CURRENT (A)
(%
V+ = 6V
V+ = 28V
V+ = 12V
MAX1653
f = 300kHz
igh-Efficiency, PWM, Step-Down
DC-DC Controllers in 16-Pin QSOPMAX1654
SHDN
-5V
OUTPUT
+5V
OUTPUT
INPUT
6V TO 30V
BST
PGND
CSH
CSL
REF
FROM
REF
SYNC
GND
SECFB
Typical Operating Circuits (continued)
igh-Efficiency, PWM, Step-DowDC-DC Controllers in 16-Pin QSOPEFFICIENCY vs.
LOAD CURRENT (5V/3A CIRCUIT)
X1652 toc04a
LOAD CURRENT (A)
(%
V+ = 28V
V+ = 6V
V+ = 12V
MAX1653
f = 300kHz
___________________________________Typical Operating Characteristics (continued)(Circuit of Figure 1, SKIP= GND, TA = +25°C, unless otherwise noted.)
EFFICIENCY vs.
LOAD CURRENT (3.3V/5A CIRCUIT)
1652 toc04
LOAD CURRENT (A)
(%
V+ = 6V
V+ = 28V
V+ = 12VMAX1653
f = 300kHz10155202530
PWM-MODE SUPPLY CURRENT vs.
INPUT VOLTAGE (3.3V/3A CIRCUIT)AX1652 toc07
INPUT VOLTAGE (V)
(m
MAX1653
SKIP = VL
f = 300kHz
NO LOAD
EFFICIENCY vs.
LOAD CURRENT (1.8V/2.5A CIRCUIT)
AX1652 toc05
LOAD CURRENT (A)
(%V+ = 6V
V+ = 24V
V+ = 12V
MAX1655
f = 300kHz
IDLE-MODE SUPPLY CURRENT vs.
INPUT VOLTAGE (3.3V/3A CIRCUIT)
X1652 toc06
INPUT VOLTAGE (V)
(m
MAX1653
SKIP = 0
NO LOAD10155202530
SHUTDOWN SUPPLY CURRENT
vs. INPUT VOLTAGEX1652 toc08
INPUT VOLTAGE (V)
(m
SHDN = 0V 10015050200250300350400
REF LOAD-REGULATION ERROR
vs. REF LOAD CURRENT1652 toc010
LOAD CURRENT (µA)
(m
MAX1652 MAXIMUM SECONDARY OUTPUT
CURRENT vs. SUPPLY VOLTAGE
AX1652 toc12
SUPPLY VOLTAGE (V)
(mVSEC > 12.75V,
+5V OUTPUT > 4.75V,
CIRCUIT OF FIGURE 9
+5V LOAD = 0A
+5V LOAD = 3A2030104050607080
VL LOAD-REGULATION ERROR
vs. VL LOAD CURRENTX1652 toc011
LOAD CURRENT (mA)
(m
OUTPUT
VOLTAGE
LOAD
CURRENT
100mV/div,
2A/div
TIME (10ms)
VIN = 15V, 3.3V/3A CIRCUIT
LOAD-TRANSIENT RESPONSEMAX1652-16
OUTPUT
VOLTAGE
VOLTAGE
10mV/div,
5V/div
TIME (5ms)
VIN = 5.1V, NO LOAD, 3.3V/3A CIRCUIT,
SET TO 5V OUTPUT (FB = VL)
DROPOUT WAVEFORMSMAX1652-15
igh-Efficiency, PWM, Step-Down
DC-DC Controllers in 16-Pin QSOPOUTPUT
VOLTAGE
VOLTAGE
10mV/div,
5V/div
TIME (1ms)
VIN = 6V, 3.3V/3A CIRCUIT
PULSE-WIDTH-MODULATION
MODE WAVEFORMSMAX1652-13
OUTPUT
VOLTAGE
VOLTAGE
50mV/div,
5V/div
TIME (2.5ms)
ILOAD = 300mA, VIN = 10V, 3.3V/3A CIRCUIT
IDLE-MODE WAVEFORMSMAX1652-14
Typical Operating Characteristics (continued)(Circuit of Figure 1, SKIP= GND, TA = +25°C, unless otherwise noted.)
DROPOUT VOLTAGE vs.
LOAD CURRENT (3.3V/3A CIRCUIT)
AX1652 toc09
LOAD CURRENT (A)
(m
OUTPUT SET FOR 5V (FB = VL)
VOUT > 4.85V
f = 150kHz
f = 300kHz
igh-Efficiency, PWM, Step-DowDC-DC Controllers in 16-Pin QSOP
Pin DescriptionDual Mode is a trademark of Maxim Integrated Products.
SKIP
(MAX1653/
MAX1655)
Disables pulse-skipping mode when high. Connect to GND for normal use. Don’t leave SKIP
unconnected.With SKIPgrounded, the device will automaticallychange from pulse-skipping operation to full PWM opera-
tion when the load current exceeds approximately 30% of maximum (Table 3).DHHigh-Side Gate-Drive Output. Normally drives the main buck switch. DH is a floating driver output that swings
from LX to BST, riding on the LX switching-node voltage. LXSwitching Node (inductor) Connection. Can swing 2V below ground without hazard.BSTBoost Capacitor Connection for High-Side Gate Drive (0.1μF) DLLow-Side Gate-Drive Output. Normally drives the synchronous-rectifier MOSFET. Swings from 0V to VL.
NAMEFUNCTIONSSSoft-Start Timing Capacitor Connection. Ramp time to full current limit is approximately 1ms/nF.
SECFB
(MAX1652/
MAX1654)
Secondary Winding Feedback Input. Normally connected to a resistor divider from an auxiliary output.
Don’t leave SECFB unconnected.MAX1652: SECFB regulates at VSECFB = 2.50V. Tie to VL if not used. MAX1654: SECFB regulates at VSECFB = 0V. Tie to a negative voltage through a high-value current-
limiting resistor (IMAX= 100μA) if not used.
PINREFReference Voltage Output. Bypass to GND with 0.33μF minimum.FB
Feedback Input. Regulates at the feedback voltage in adjustable mode. FB is a Dual ModeTMinput that also
selects the fixed output voltage settings as follows: Connect to GND for 3.3V operation.Connect to VL for 5V operation.Connect FB to a resistor divider for adjustable mode. FB can be driven with +5V CMOS logic in order to
change the output voltage under system control.SHDNShutdown Control Input, active low. Logic threshold is set at approximately 1V (VTHof an internal N-channel
MOSFET). Tie SHDNto V+ for automatic start-up.SYNC
Oscillator Synchronization and Frequency Select. Tie to GND or VL for 150kHz operation; tie to REF for
300kHz operation. A high-to-low transition begins a new cycle. Drive SYNC with 0 to 5V logic levels (see the
Electrical Characteristicstable for VIHand VILspecifications). SYNC capture range is 190kHz to 340kHz.GNDLow-Noise Analog Ground and Feedback Reference PointPGNDPower GroundVL
5V Internal Linear-Regulator Output. VL is also the supply voltage rail for the chip. VL is switched to the out-
put voltage via CSL (VCSL> 4.5V) for automatic bootstrapping. Bypass to GND with 4.7μF. VL can supply up
to 5mA for external loads.V+Battery Voltage Input (4.5V to 30V). Bypass V+ to PGND close to the IC with a 0.1μF capacitor. Connects to a
linear regulator that powers VL. CSLCurrent-Sense Input, low side. Also serves as the feedback input in fixed-output modes.CSHCurrent-Sense Input, high side. Current-limit level is 100mV referred to CSL.
igh-Efficiency, PWM, Step-Down DC-DC Controllers in 16-Pin QSOPandard Application CircuitsIt’s easy to adapt the basic MAX1653 single-output 3.3V
buck converter (Figure 1) to meet a wide range of appli-
cations with inputs up to 30V (limited by choice of exter-
nal MOSFET). Simply substitute the appropriate
components from Table 1 (candidate suppliers are pro-
vided in Table 2). These circuits represent a good set of
trade-offs among cost, size, and efficiency while staying
within the worst-case specification limits for stress-relat-
ed parameters such as capacitor ripple current.
Don’t change the frequency of these circuits without
first recalculating component values (particularly induc-
tance value at maximum battery voltage).
For a discussion of dual-output circuits using the
MAX1652 and MAX1654, see Figure 9 and the
Secondary Feedback-Regulation Loopsection.
tailed DescriptionThe MAX1652 family are BiCMOS, switch-mode power-
supply controllers designed primarily for buck-topology
regulators in battery-powered applications where high
efficiency and low quiescent supply current are critical.
The parts also work well in other topologies such as
boost, inverting, and Cuk due to the flexibility of their
floating high-speed gate driver. Light-load efficiency is
enhanced by automatic idle-mode operation—a vari-
able-frequency pulse-skipping mode that reduces
losses due to MOSFET gate charge. The step-down
power-switching circuit consists of two N-channel
MOSFETs, a rectifier, and an LC output filter. The out-
put voltage is the average of the AC voltage at the
switching node, which is adjusted and regulated by
changing the duty cycle of the MOSFET switches. The
gate-drive signal to the N-channel high-side MOSFET
must exceed the battery voltage and is provided by a
flying capacitor boost circuit that uses a 100nF capaci-
tor connected to BST.
MAX1653
CSL
CSH
SYNCFB117
CMPSH-3
150kHz/300kHz
JUMPER
NOTE: KEEP CURRENT-SENSE LINES SHORT AND CLOSE
TOGETHER. SEE FIGURE 8.
REF3
GND4
+5V AT
5mA
+3.3V
OUTPUT
GND
OUT
BST
LOW-NOISE
CONTROL
PGND
SKIPON/OFF
CONTROL
SHDN
INPUT
REF OUTPUT
+2.5V AT 100mA
0.33mF
4.7mF
0.1mF
0.01mF
(OPTIONAL)
0.1mFL1
Figure 1. Standard 3.3V Application Circuit (see Table 1 for Component Values)
igh-Efficiency, PWM, Step-DowDC-DC Controllers in 16-Pin QSOP
Table 1. Component Selection for Standard Applications
COMPONENT3.3V at 1A3.3V at 2A5V/3.3V at 3A3.3V at 5A1.8V at 2.5AFrequency300kHz300kHz300kHz300kHz150kHz
Q1 High-Side
MOSFET
International Rectifier
1/2 IRF7101
International Rectifier
1/2 IRF7303 or
Fairchild
Semiconductor
1/2 NDS8936
International Rectifier
IRF7403 or
Fairchild
Semiconductor
NDS 8410A
Fairchild
Semiconductor
FDS6680
International Rectifier
1/2 IRF7303 or
Fairchild
Semiconductor
1/2 NDS8936
Q2 Low-Side
MOSFET
International Rectifier
1/2 IRF7101
International Rectifier
1/2 IRF7303 or
Fairchild
Semiconductor
1/2 NDS8936
International Rectifier
IRF7403 or
Fairchild
Semiconductor
NDS 8410A
Fairchild
Semiconductor
FDS6680
International Rectifier
1/2 IRF7303 or
Fairchild
Semiconductor
1/2 NDS8936
C1 Input
Capacitor
10μF, 35V
AVX
TPSD106M035R0300
22μF, 35V
AVX
TPSE226M035R0300
(2) 22μF, 35V
AVX
TPSE226M035R0300
(3) 22μF, 35V
AVX
TPSE226M035R0300
10μF, 25V ceramic
Taiyo Yuden
TMK325F106Z
C2 Output
Capacitor
100μF, 6.3V
AVX TPSC107M006R
220μF, 10V
AVX
TPSE227M010R0100
or Sprague
594D227X001002T
470μF, 6V (for 3.3V)
Kemet
T510X477M006AS
(2) 220μF, 10V (for 5V)
AVX
TPSE227M010R011
(3) 330μF, 10V
Sprague
594D337X0010R2T
(2) 470μF, 6V
Kemet
T510X477M006AS
470μF, 4V
Sprague
594D477X0004R2T
470μF, 6V
Kemet
T510X477M006AS
D1 Rectifier1N5819 or Motorola
MBR0520L
1N5819 or Motorola
MBRS130LT3
1N5819 or Motorola
MBRS130LT3
1N5821 or Motorola
MBRS340T3
1N5817 or Motorola
MBRS130LT3
R1 Sense
Resistor
70mΩ
Dale WSL-1206-R070F
or IRC LR2010-01-R070
33mΩ
Dale WSL-2010-R033F
or IRC LR2010-01-R033
25mΩ
Dale WSL-2010-R025F
or IRC LR2010-01-R025
12mΩ
Dale WSL-2512-R012F
30mΩ
Dale WSL-2010-R030F
or IRC LR2010-01-R030
L1 Inductor33μH
Sumida CDR74B-330
15μH
Sumida CDR105B-150
10μH
Sumida CDRH125-100
4.7μH
Sumida CDRH127-4R7
15μH
Sumida CDRH125-150
Table 2. Component Suppliers* Distributor
[1] 602-994-6430602-303-5454Motorola
[1] 408-986-1442408-986-0424Kemet
[1] 512-992-3377512-992-7900IRC
[1] 408-721-1635408-822-2181Fairchild
[1] 605-665-1627605-668-4131Dale
[1] 561-241-9339561-241-7876Coiltronics
[1] 847-639-1469847-639-6400Coilcraft
[1] 516-435-1824516-435-1110Central Semiconductor
[1] 803-626-3123803-946-0690AVX
FACTORY FAX
[Country Code]USA PHONEMANUFACTURERInput Range4.75V to 28V4.75V to 28V4.75V to 28V4.75V to 28V4.75V to 22V
[1] 408-573-4159408-573-4150Taiyo Yuden
[81] 3-3607-5144847-956-0666Sumida
[1] 603-224-1430603-224-1961Sprague
[1] 408-970-3950408-988-8000
800-554-5565Siliconix
[81] 7-2070-1174619-661-6835Sanyo
[81] 3-3494-7414805-867-2555*NIEC
[1] 814-238-0490814-237-1431
800-831-9172Murata
FACTORY FAX
[Country Code]USA PHONEMANUFACTURER[1] 702-831-3521702-831-0140Transpower Technologies
[1] 714-960-6492714-969-2491Matsuo
[1] 310-322-3332310-322-3331International Rectifier
[1] 847-390-4405847-390-4461TDK
igh-Efficiency, PWM, Step-Down DC-DC Controllers in 16-Pin QSOPThe MAX1652–MAX1655 contain nine major circuit
blocks, which are shown in Figure 2:
PWM Controller Blocks:Multi-Input PWM ComparatorCurrent-Sense CircuitPWM Logic BlockDual-Mode Internal Feedback MuxGate-Driver OutputsSecondary Feedback Comparator
Bias Generator Blocks: +5V Linear RegulatorAutomatic Bootstrap Switchover Circuit +2.50V Reference
These internal IC blocks aren’t powered directly from
the battery. Instead, a +5V linear regulator steps down
the battery voltage to supply both the IC internal rail (VL
pin) as well as the gate drivers. The synchronous-
switch gate driver is directly powered from +5V VL,
while the high-side-switch gate driver is indirectly pow-
ered from VL via an external diode-capacitor boost cir-
cuit. An automatic bootstrap circuit turns off the +5V
linear regulator and powers the IC from its output volt-
age if the output is above 4.5V.
PWM Controller BlockThe heart of the current-mode PWM controller is a
multi-input open-loop comparator that sums three sig-
nals: output voltage error signal with respect to the ref-
erence voltage, current-sense signal, and slope
compensation ramp (Figure 3). The PWM controller is a
direct summing type, lacking a traditional error amplifi-
er and the phase shift associated with it. This direct-
summing configuration approaches the ideal of
cycle-by-cycle control over the output voltage.
Under heavy loads, the controller operates in full PWM
mode. Each pulse from the oscillator sets the main
PWM latch that turns on the high-side switch for a peri-
od determined by the duty factor (approximately
VOUT/VIN). As the high-side switch turns off, the syn-
chronous rectifier latch is set. 60ns later the low-side
switch turns on, and stays on until the beginning of the
next clock cycle (in continuous mode) or until the
inductor current crosses zero (in discontinuous mode).
Under fault conditions where the inductor current
exceeds the 100mV current-limit threshold, the high-
side latch resets and the high-side switch turns off.
If the load is light in Idle Mode (SKIP= low), the induc-
tor current does not exceed the 25mV threshold set by
the Idle Mode comparator. When this occurs, the con-
troller skips most of the oscillator pulses in order to
reduce the switching frequency and cut back gate-
charge losses. The oscillator is effectively gated off at
light loads because the Idle Mode comparator immedi-
ately resets the high-side latch at the beginning of each
cycle, unless the feedback signal falls below the refer-
ence voltage level.
When in PWM mode, the controller operates as a fixed-
frequency current-mode controller where the duty ratio
is set by the input/output voltage ratio. The current-
mode feedback system regulates the peak inductor
current as a function of the output voltage error signal.
Since the average inductor current is nearly the same
as the peak current, the circuit acts as a switch-mode
transconductance amplifier and pushes the second out-
put LC filter pole, normally found in a duty-factor-
controlled (voltage-mode) PWM, to a higher frequency.
To preserve inner-loop stability and eliminate regenera-
tive inductor current “staircasing,” a slope-compensa-
tion ramp is summed into the main PWM comparator to
reduce the apparent duty factor to less than 50%.
The relative gains of the voltage- and current-sense
inputs are weighted by the values of current sources
that bias three differential input stages in the main PWM
comparator (Figure 4). The relative gain of the voltage
comparator to the current comparator is internally fixed
at K = 2:1. The resulting loop gain (which is relatively
low) determines the 2% typical load regulation error.
The low loop-gain value helps reduce output filter
capacitor size and cost by shifting the unity-gain
crossover to a lower frequency.
The output filter capacitor C2 sets a dominant pole in
the feedback loop. This pole must roll off the loop gain
to unity before the zero introduced by the output
capacitor’s parasitic resistance (ESR) is encountered
(see Design Proceduresection). A 12kHz pole-zero
cancellation filter provides additional rolloff above the
unity-gain crossover. This internal 12kHz lowpass com-
pensation filter cancels the zero due to the filter capaci-
tor’s ESR. The 12kHz filter is included in the loop in
both fixed- and adjustable-output modes.
Synchronous-Rectifier Driver (DL Pin) Synchronous rectification reduces conduction losses in
the rectifier by shunting the normal Schottky diode with
a low-resistance MOSFET switch. The synchronous rec-
tifier also ensures proper start-up of the boost-gate driv-
er circuit. If you must omit the synchronous power
MOSFET for cost or other reasons, replace it with a
small-signal MOSFET such as a 2N7002.
If the circuit is operating in continuous-conduction mode,
the DL drive waveform is simply the complement of the
DH high-side drive waveform (with controlled dead
time to prevent cross-conduction or “shoot-through”).
igh-Efficiency, PWM, Step-DowDC-DC Controllers in 16-Pin QSOPMAX1652
MAX1653
MAX1654
MAX1655
CSL
CSH
REF
GND
ADJ FB
5V FB
3.3V FB
SYNC
LPF
12kHz
PWM
COMPARATOR
OUT
BATTERY VOLTAGE
4.5V
CSL
+5V AT 5mA
BST
PGND
SECFB
MAIN
OUTPUT
AUXILIARY
OUTPUT
SHDN
PWM
LOGIC
SHDN
ON/OFF
+2.50V
AT 100mA
+5V LINEAR
REGULATOR
+2.50V
REF
Figure 2. MAX1652–MAX1655 Functional Diagram
igh-Efficiency, PWM, Step-Down DC-DC Controllers in 16-Pin QSOPSHOOT-
THROUGH
CONTROL
25mVQ
LEVEL
SHIFTs
SINGLE-SHOT
MAIN PWM
COMPARATOR
OSC
LEVEL
SHIFT
CURRENT
LIMIT
24R2.5VA
SYNCHRONOUS-
RECTIFIER CONTROL
2.5V (1V, MAX1655)
SHDN
-100mV
(NOTE 1)
COMPARATOR
CSH
CSL
FROM
FEEDBACK
DIVIDER
BST
PGND
SLOPE COMP
IDLE MODE
COMPARATOR
SKIP
(MAX1653/
MAX1655
ONLY)
REF (MAX1652)
GND (MAX1654)
MAX1652, MAX1654 ONLYSECFB
NOTE 1: COMPARATOR INPUT POLARITIES
ARE REVERSED FOR THE MAX1654.
Figure 3. PWM Controller Detailed Block Diagram
