MAX758ACPA+ ,Adjustable, PWM, Step-Down RegulatorFeaturesThe MAX750A/MAX758A are adjustable-output, CMOS, ♦ Up to 750mA Load Currentsstep-down, DC-D ..
MAX758ACWE ,Adjustable / Step-Down / Current-Mode PWM RegulatorsELECTRICAL CHARACTERISTICS(Circuit of Figure 3, V+ = 9V for the MAX750A, V+ = 12V for the MAX758A, ..
MAX758AEPA ,Adjustable / Step-Down / Current-Mode PWM RegulatorsFeaturesThe MAX750A/MAX758A are adjustable-output, CMOS, ' Up to 750mA Load Currentsstep-down, DC-D ..
MAX758AEPA ,Adjustable / Step-Down / Current-Mode PWM RegulatorsFeaturesThe MAX750A/MAX758A are adjustable-output, CMOS, ' Up to 750mA Load Currentsstep-down, DC-D ..
MAX758AEWE ,Adjustable / Step-Down / Current-Mode PWM RegulatorsMAX750A/MAX758A19-0195; Rev 0; 10/93Adjustable, Step-Down,Current-Mode PWM Regulators_______________
MAX759CPD ,-5V,-12V,-15V, and Adjustable Inverting Current-Mode PWM RegulatorsELECTRICAL CHARACTERISTICS
Bootstrapped Mode (Circuit of Figure 1, V+ = w, ILOAD = 0mA, DRV- = V ..
MB6M ,MINIATURE GLASS PASSIVATED SINGLE-PHASE BRIDGE RECTIFIERThermal Characteristics (TA = 25°C unless otherwise noted)Parameter Symbol MB2M MB4M MB6M UnitDevic ..
MB6S ,Bridge RectifiersThermal Characteristics (T = 25°C unless otherwise noted)AParameter Symbol MB2S MB4S MB6S UnitDevic ..
MB7117E , Schottky TTL 2048-Bit Bipolar Programmable Read-Only Memory
MB71A38-25 , PROGRAMMABLE SCHOTTKY 16384-BIT READ ONLY MEMORY
MAX750ACSA+-MAX750ACSA+T-MAX750AESA+-MAX758ACPA+
Adjustable, PWM, Step-Down Regulator
_______________General DescriptionThe MAX750A/MAX758A are adjustable-output, CMOS,
step-down, DC-DC switching regulators. The
MAX758A accepts inputs from 4V to 16V and delivers
750mA, while the MAX750A accepts inputs from 4V to
11V and delivers 450mA. Typical efficiencies are 85%
to 90%. Typical quiescent current is 1.7mA, or only
6μA in shutdown mode. The output does not exhibit
any ripple at subharmonics of the switching frequency
over its specified range.
Pulse-width-modulation (PWM) current-mode control
provides precise output regulation and excellent tran-
sient responses. Output voltage accuracy is guaran-
teed to be ±4.5% plus feedback-resistor tolerance over
line, load, and temperature variations. Fixed-frequency
switching and absence of subharmonic ripple allows
easy filtering of output ripple and noise, as well as the
use of small external components. These regulators
require only a single inductor value to work in most
applications, so no inductor design is necessary.
________________________ApplicationsCellular Phones & Radios
Portable Communications Equipment
Portable Instruments
Computer Peripherals
____________________________FeaturesUp to 750mA Load Currents160kHz High-Frequency, Current-Mode PWM85% to 96% Efficiencies33μH or 100μH Pre-Selected Inductor Value,
No Component Design Required1.7mA Quiescent Supply Current6μA Shutdown Supply CurrentAdjustable Output VoltageOvercurrent, Soft-Start, and Undervoltage
Lockout ProtectionCycle-by-Cycle Current Limiting8-Pin DIP/SO Packages (MAX750A)
______________Ordering Information
Ordering Information continued on last page.* Contact factory for dice specifications.
**Contact factory for availability and processing to MIL-STD-883.
Adjustable, Step-Down,
Current-Mode PWM Regulators
________________________________________________________________Maxim Integrated Products1GND
I.C.CC
REF
SHDN
DIPTOP VIEW
MAX750A
MAX758A
GND
I.C.CC
REF
MAX750A
SHDN
_________________Pin Configurations
OUTPUT ADJ.
FROM
VREF TO V+
INPUT
4V TO 16VGNDSS
MAX750A
MAX758A
SHDN
REF
33µH
ON/OFF
__________Typical Operating Circuit
Call toll free 1-800-998-8800 for free samples or literature.19-0195; Rev 0; 10/93
PARTTEMP. RANGEPIN-PACKAGE
MAX750ACPA0°C to +70°C8 Plastic DIP
MAX750ACSA0°C to +70°C8 SO
MAX750AC/D0°C to +70°CDice*
MAX750AMJA-55°C to +125°C8 CERDIP**
MAX750AESA-40°C to +85°C8 SO
MAX750AEPA-40°C to +85°C8 Plastic DIP
Pin Configurations continued on last page.
Adjustable, Step-Down,
Current-Mode PWM Regulators_______________________________________________________________________________________Pin Voltages
V+ (MAX750A).........................................................+12V, -0.3V
V+ (MAX758A).........................................................+18V, -0.3V
LX (MAX750A)....................................(V+ - 12V) to (V+ + 0.3V)
LX (MAX758A)....................................(V+ - 21V) to (V+ + 0.3V)
SS, CC, SHDN.............................................-0.3V to (V+ + 0.3V)
Peak Switch Current (ILX).........................................................2A
Reference Current (IREF)...................................................2.5mA
Power Dissipation (TA= +70°C)
8-Pin Plastic DIP (derate 9.09mW/°C above +70°C).....727mW
8-Pin SO (derate 5.88mW/°C above +70°C)..................471mW
16-Pin Wide SO (derate 9.52mW/°C above +70°C)......762mW
8-Pin CERDIP (derate 8.00mW/°C above +70°C)..........640mW
Operating Temperature Ranges:
MAX75_AC_ _.......................................................0°C to +70°C
MAX75_AE_ _....................................................-40°C to +85°C
MAX75_AMJA..................................................-55°C to +125°C
Junction Temperatures:
MAX75_AC_ _/AE_ _......................................................+150°C
MAX75_AMJA................................................................+175°C
Storage Temperature Range.............................-65°C to +160°C
Lead Temperature (soldering, 10sec).............................+300°C
ELECTRICAL CHARACTERISTICS(Circuit of Figure 3, V+ = 9V for the MAX750A, V+ = 12V for the MAX758A, VOUT= 5V, R2 = 40.20kΩ, R3 = 13.0kΩ, ILOAD= 0mA, = TMINto TMAX, 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.
PARAMETERUNITSLoad Regulation0.0005
%/VLine Regulation0.15
Input Voltage Range4.011.0V
%/mA
Efficiency92%
Supply Current1.73.0mA
Output Voltage
(Note 1)V
6.0100.0μA
2.0Shutdown Input
Threshold0.25V
1.0μA
Short-Circuit Current1.5A
CONDITIONSSHDN= 0V
ILOAD= 0mA to 450mA
VIH
V+ = 4.0V to 16.0V
V+ = 4.0V to 11.0V
ILOAD= 0mA to 750mA
V+ = 9.0V, ILOAD= 300mA
VIL
V+ = 12V, ILOAD= 750mA
ABSOLUTE MAXIMUM RATINGSV+ = 6.0V to 11.0V;
0mA < ILOAD< 450mA for MAX750AC,
0mA < ILOAD< 450mA for MAX750AE,
0mA < ILOAD< 300mA for MAX750AM
V+ = 6.0V to 16.0V;
0mA < ILOAD< 450mA for MAX758AC/AE,
0mA < ILOAD< 350mA for MAX758AM
V+ = 10.2V to 16.0V,
0mA < ILOAD< 750mA
Shutdown Supply
Current (Note 2)
Shutdown Input
Leakage Current
MAX750A
MINTYPMAX
MAX758A
MINTYPMAX4.755.005.25
Adjustable, Step-Down,
Current-Mode PWM Regulators
_______________________________________________________________________________________3
Note 1:Output voltage tolerance over temperature is ±4.5% plus the tolerances of R3 and R4 in Figure 3.
Note 2:The standby current typically settles to 25μA (over temperature) within 2 seconds; however, to decrease test time, the part
is guaranteed at a 100μA maximum value.
PARAMETERMAX758A
MINTYPMAX
MAX750A
MINTYPMAXUNITS3.754.00Undervoltage
Lockout3.5VOn Resistance0.5Ω
LX Leakage Current1.0μA
Reference Voltage1.151.221.30V
Reference Drift50ppm/°C
Oscillator FrequencykHz
Compensation Pin
Impedance7500Ω
CONDITIONSV+ rising
V+ falling
ILX= 500mA= +25°C
ELECTRICAL CHARACTERISTICS (continued)(Circuit of Figure 3, V+ = 9V for the MAX750A, V+ = 12V for the MAX758A, VOUT= 5V, R2 = 40.20kΩ, R3 = 13.0kΩ, ILOAD= 0mA, = TMINto TMAX, unless otherwise noted.)
__________________________________________Typical Operating Characteristics(Circuit of Figure 3, VOUT= 5V, TA= +25°C, unless otherwise noted.)
MAX750A
EFFICIENCY vs. OUTPUT CURRENT
MAX750A/58A-1
OUTPUT CURRENT (mA)
(%
V+ = 5.5V
V+ = 7V
V+ = 9V
V+ = 11V
(NOTES 3, 6)
MAX758A
EFFICIENCY vs. OUTPUT CURRENT
MAX750A/58A-2
OUTPUT CURRENT (mA)
(%
V+ = 6V
V+ = 8V
V+ = 12V
V+ = 16V
(NOTES 3, 6)
130170210
Adjustable, Step-Down,
Current-Mode PWM Regulators_______________________________________________________________________________________
MAX758A
PEAK INDUCTOR CURRENT
vs. OUTPUT CURRENTMAX1750A/58A-4
OUTPUT CURRENT (mA)
IN
T (m
V+ = 6.6V
V+ 8.0V TO 16.0V
L1 = 100µH
C4 = 300µF
MAX758A
PEAK INDUCTOR CURRENT
vs. OUTPUT CURRENTAX1750A/58A-5
OUTPUT CURRENT (mA)
IN
(m
L1 = 18µH
C4 = 1000µF600
V+ = 10.2V
V+ = 8.0V
V+ = 6.6V
V+ = 6.0V
OSCILLATOR FREQUENCY
vs. SUPPLY VOLTAGE
MAX1750A/58A-6
SUPPLY VOLTAGE (V)
ILL
FR
(k
MAX750A
MAX758A
(NOTE 3)
MAX758A
NO-LOAD SUPPLY CURRENT vs. SUPPLY VOLTAGEMAX1750A/58A-7
SUPPLY VOLTAGE (V)
-LO
(m
UNDERVOLTAGE
LOCKOUT V+ FALLING
(OPERATION ENDS)
UNDERVOLTAGE
LOCKOUT V+ RISING
(OPERATION BEGINS)
(NOTES 3, 5)
NO-LOAD SUPPLY CURRENT
vs. TEMPERATURE
MAX750A/58A-8
TEMPERATURE (°C)
(m
MAX750A, V+ = 9.0V
MAX758A, V+ = 12.0V
(NOTES 4, 5)
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
MAX750A/58A-9
TEMPERATURE (°C)
T (m
MAX758A ONLY, V+ = 16V
MAX758A ONLY, V+ = 12V
V+ = 9V
V+ = 6V
(NOTES 4, 5)
_____________________________Typical Operating Characteristics (continued)(Circuit of Figure 3, VOUT= 5V, TA= +25°C, unless otherwise noted.)
TEMPERATURE (°C)
ILL
R FR
(k
MAX750A
OSCILLATOR FREQUENCY vs. TEMPERATURE140 V+ = 9.0V
V+ = 7.0V
(NOTE 4)
V+ = 5.5V
V+ = 11.0V
TEMPERATURE (°C)
ILL
(kH
MAX758A
OSCILLATOR FREQUENCY vs. TEMPERATURE V+ = 6.0V
V+ = 16.0V
V+ = 12.0V
V+ = 9.0V
(NOTE 4)
Adjustable, Step-Down,
Current-Mode PWM Regulators
_______________________________________________________________________________________5MAXIMUM OUTPUT CURRENT
vs. SUPPLY VOLTAGE
MAX750A/58A-10
SUPPLY VOLTAGE (V)
(m12
MAX750A
MAX758A
(NOTES 3, 6)
MAXIMUM OUTPUT CURRENT
vs. SUPPLY VOLTAGE, R1 OMITTED
MAX750A/58A-11
SUPPLY VOLTAGE (V)
(m12
MAX750A
MAX758A
(NOTES 3, 6)
MAX758A
SWITCHING WAVEFORMS
CONTINUOUS CONDUCTIONs/div
A: SWITCH VOLTAGE (LX PIN), 5V/div, 0V TO +12V
B: INDUCTOR CURRENT, 200mA/div
C: OUTPUT VOLTAGE RIPPLE, 50mV/div
COUT= 390mF, V+ = 12V, IOUT= 150mA
MAX758A
SWITCHING WAVEFORMS
DISCONTINUOUS CONDUCTIONs/div
A: SWITCH VOLTAGE (LX PIN), 5V/div, 0V TO +12V
B: INDUCTOR CURRENT, 100mA/div
C: OUTPUT VOLTAGE RIPPLE, 50mV/div
COUT= 390mF, V+ = 12V, IOUT= 20mA
12V
200mA
0mA
12V
100mA
0mA
_____________________________Typical Operating Characteristics (continued)(Circuit of Figure 3, VOUT= 5V, TA= +25°C, unless otherwise noted.)
Adjustable, Step-Down,
Current-Mode PWM Regulators_______________________________________________________________________________________
MAX750A
LOAD-TRANSIENT RESPONSE50ms/div
A: VOUT, 50mV/div, AC-COUPLED
B: IOUT, 200mA/div, 20mA TO 300mA
V+ = 9V
MAX758A
LOAD-TRANSIENT RESPONSE50ms/div
A: VOUT, 50mV/div, AC-COUPLED
B: IOUT, 500mA/div, 50mA TO 750mA
V+ = 12V
300mA
20mA
750mA
50mA
MAX750A
LINE-TRANSIENT RESPONSE100ms/div
A: VOUT, 50mV/div, AC-COUPLED
B: V+, 5V/div, 6.0V TO 11.0V
IOUT= 300mA
MAX758A
LINE-TRANSIENT RESPONSE100ms/div
A: VOUT, 50mV/div, AC-COUPLED
B: V+, 5V/div, 10.2V TO 16.0V
IOUT= 750mA
11V
16V
10.2V
_____________________________Typical Operating Characteristics (continued)(Circuit of Figure 3, VOUT= 5V, TA= +25°C, unless otherwise noted.)
Note 3:Commercial temperature range external component values in Table 2.
Note 4:Wide temperature range external component values in Table 2.
Note 5:Supply current includes all external component leakage currents. External capacitor leakage currents dominate at TA> +85°C.
C3 and C4 = Sanyo Oscon through-hole capacitors.
Note 6:Operation beyond the specifications listed in the Electrical Characteristicsmay exceed the power dissipation ratings of the device.
Adjustable, Step-Down,
Current-Mode PWM Regulators
_______________________________________________________________________________________7
NAMEFUNCTIONSHDNShutdown—active low. Ground to power-down chip, tie to V+ for normal operation.
Output voltage falls to 0V when SHDNis low.REFSSSoft-Start. Capacitor between SS and GND provides soft-start and short-circuit protec-
tion. 510kΩresistor from SS to SHDNprovides current boost.CCI.C.Internal Connection. Make no external connection to this pin.GNDGround*LXDrain of internal P-channel power MOSFET*V+N.C.No Connect—not internally connected.
10, 11
12, 13, 14
1, 15, 16
4, 5, 6
______________________________________________________________Pin Description
PIN
8-PIN 16-PIN
DIP/SO WIDE SOReference Voltage Output (+1.22V) supplies up to 100μA for external loads. Bypass to
GND with a capacitor that does not exceed 0.047μF.
External voltage divider feedback point. When an external voltage divider is connected from
the output voltage to CC and GND, this pin becomes the feedback input for adjusting the
output voltage. Connect a 330pF compensation capacitor between the output and CC.
Supply Voltage Input. Bypass to GND with 1.0μF ceramic and large-value electrolytic capaci-
tors in parallel. The 1μF capacitor must be as close to the V+ and GND pins are possible.*
*16-Pin Wide SO: All pins with the same name must be connected together externally.
_______________Detailed DescriptionThe MAX750A/MAX758A switch-mode regulators use a
current-mode pulse-width-modulation (PWM) control
system coupled with a simple step-down (buck) regula-
tor topography. Input voltages range from 4V to 11V for
the MAX750A, and from 4V to 16V for the MAX758A.
The current-mode PWM architecture provides cycle-by-
cycle current limiting, improved load transient response
characteristics, and simpler outer-loop design.
The controller consists of two feedback loops: an inner
(current) loop that monitors the switch current via the
current-sense resistor and amplifier, and an outer (volt-
age) loop that monitors the output voltage through the
error amplifier (Figure 1). The inner loop performs
cycle-by-cycle current limiting, truncating the power-
transistor on-time when the switch current reaches a
predetermined threshold. This threshold is determined
by the outer loop. For example, a sagging output volt-
age produces an error signal that raises the threshold,
allowing the circuit to store and transfer more energy
during each cycle.
Programmable Soft-StartFigures 1 and 2 show a capacitor and a resistor connect-
ed to the soft-start (SS) pin to ensure an orderly power-
up. Typical values are 0.1μF and 510kΩ. SS controls
both the soft-start timing and the maximum output cur-
rent that can be delivered while maintaining regulation.
The charging capacitor slowly raises the clamp on the
error-amplifier output voltage, limiting surge currents at
power-up by slowly increasing the cycle-by-cycle current-
limit threshold. The 510kΩresistor sets the soft-start
clamp at a value high enough to maintain regulation, even
at currents exceeding 1A. This resistor is not necessary
for lower current loads. Refer to the Maximum Output
Current vs. Supply Voltage, No. R1 graph in the Typical
Operating Characteristics. Table 1 lists timing character-
istics for selected capacitor values and circuit conditions.
The overcurrent comparator trips if the load exceeds
approximately 1.5A. A soft-start cycle begins when
either an undervoltage or overcurrent fault condition
triggers an internal transistor to discharge the soft-
start capacitor to ground. A soft-start cycle also
begins at power-up and when coming out of the shut-
down mode.
Adjustable, Step-Down,
Current-Mode PWM Regulators_______________________________________________________________________________________
Overcurrent LimitingThe overcurrent comparator triggers when the load cur-
rent exceeds approximately 1.5A. On each clock
cycle, the output FET turns on and attempts to deliver
current until cycle-by-cycle or overcurrent limits are
exceeded. Note that the soft-start capacitor must be
greater than 0.01μF for overcurrent protection to func-
tion properly. A typical value is 0.1μF. A soft-start
cycle is initiated when the overcurrent comparator is
triggered.
Undervoltage LockoutThe undervoltage lockout feature monitors the supply
voltage at V+ and allows operation to start when V+
rises above 3.75V. When V+ falls, operation continues
until the supply voltage falls below 3.50V. When an
undervoltage condition is detected, control logic turns
off the output power FET and discharges the soft-start
capacitor to ground. This prevents partial turn-on of
the power MOSFET and avoids excessive power dissi-
pation. The control logic holds the output power FET
off until the supply voltage rises above approximately
3.75V, at which time a soft-start cycle begins.
Shutdown ModeThe MAX750A/MAX758A are shut down by keeping
SHDNat ground. In shutdown mode, the output power
FET is held off and the output drops to 0V. The internal
reference also turns off, which causes the soft-start
capacitor to discharge. The 6μA typical standby cur-
rent includes external-component leakage currents. As
temperature increases past +85°C, the external capaci-
1.23V
BANDGAP
1M
±35%
C6
0.01µF
R1
510K
C1
0.1µF
C5
330pF
F/F
RAMP
GEN
CURRENT
SENSE AMP
OSC
RSENSE
OVERCURRENT COMPARATOR
VUVLO
SLOPE COMPENSATION
VIN
BIAS
GEN
ERROR
AMP
SS CLAMP
UNDERVOLTAGE
LOCKOUT
PWM
COMPARATOR
SHDN
GND
D1
1N5817
C4*
C2
1µF
C3*
VOUT
* SEE TABLE 3 FOR COMPONENT VALUES AND SUPPLIERS.
MAX750A
MAX758A
REF
Figure 1. Detailed Block Diagram with External Components
