Document
19-0182; Rev 3; 9/95
5V/3.3V/3V 5A Step-Down, PWM, Switch-Mode DC-DC Regulators
_______________General Description
The MAX787/MAX788/MAX789 are monolithic, bipolar, pulse-width modulation (PWM), switch-mode, step-down DC-DC regulators. Each is rated at 5A. Very few external components are needed for standard operation because the power switch, oscillator, feedback, and control circuitry are all on-chip. Employing a classic buck topology, these regulators perform high-current step-down functions. The MAX787/MAX788/MAX789 have excellent dynamic and transient response characteristics, while featuring cycle-by-cycle current limiting to protect against overcurrent faults and short-circuit output faults. They also have a wide 8V to 40V input range. Each regulator is available in a 5-pin TO-220 package. These devices have a preset 100kHz oscillator frequency and a preset current limit of 6.5A. See the MAX724/ MAX726 data sheet for more applications information.
___________________________Features
o Input Range: Up to 40V o 5A On-Chip Power Switch o Fixed Outputs: 5V (MAX787) 3.3V (MAX788) 3V (MAX789) o 100kHz Switching Frequency o Excellent Dynamic Characteristics o Few External Components o 8.5mA Quiescent Current o TO-220 Package
MAX787/MAX788/MAX789
______________Ordering Information
PART MAX787CCK MAX787ECK MAX788CCK MAX788ECK MAX789CCK MAX789ECK TEMP. RANGE 0°C to +70°C -40°C to +85°C 0°C to +70°C -40°C to +85°C 0°C to +70°C -40°C to +85°C PIN-PACKAGE 5 TO-220 5 TO-220 5 TO-220 5 TO-220 5 TO-220 5 TO-220
_______________________Applications
Distributed Power from High-Voltage Buses High-Current, High-Voltage Step-Down Multiple-Output Buck Converter
___________Product Selection Guide
PART MAX724 MAX726 MAX727 VOUT (V) Adjustable Adjustable 5 3.3 3 5 3.3 3 IOUT MAX (A) 5 2 2 2 2 5 5 5
__________Typical Operating Circuit
MAX728 MAX729 MAX787 MAX788
INPUT 8V TO 40V VIN 220µF VSW
50µH
OUTPUT 5V AT 5A
MAX789
__________________Pin Configuration
FRONT VIEW
MAX787
VC 2.7k GND 0.01µF SENSE
MBR745 470µF
MAX787 MAX788 MAX789
5 4 3 2 1
VIN VSW GND VC SENSE
5-PIN TO-220 STEP-DOWN CONVERTER
CASE IS CONNECTED TO GROUND. STANDARD PACKAGE HAS STAGGERED LEADS. CONTACT FACTORY FOR STRAIGHT LEADS.
________________________________________________________________ Maxim Integrated Products
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5V/3.3V/3V 5A Step-Down, PWM, Switch-Mode DC-DC Regulators MAX787/MAX788/MAX789
ABSOLUTE MAXIMUM RATINGS
Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45V Switch Voltage with Respect to Input Voltage. . . . . . . . . . . . . . . . 50V Switch Voltage with Respect to GND Pin (VSW negative) (Note 1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35V SENSE Pin Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V, +10V Operating Temperature Ranges MAX78_CCK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0°C to +70°C MAX78_ECK. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -40°C to +85°C Junction Temperature Ranges MAX78_CCK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0°C to +125°C MAX78_ECK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . - 40°C to +125°C Storage Temperature Range . . . . . . . . . . . . . . . . . . . -65°C to +160°C Lead Temperature (soldering, 10sec). . . . . . . . . . . . . . . . . . . . +300°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.
ELECTRICAL CHARACTERISTICS
(VIN = 25V, Tj = TMIN to TMAX, unless otherwise noted.) PARAMETER Input Supply Voltage Range ISW = 1A Switch-On Voltage (Note 1) ISW = 5A Switch-Off Leakage Supply Current (Note 3) Minimum Supply Voltage Switch-Current Limit (Note 5) Maximum Duty Cycle Tj = +25°C Switching Frequency VOUT = VSENSE = 0V (Note 5) Switching Frequency Line Regulation Error-Amplifier Voltage Gain Error-Amplifier Transconductance Error-Amplifier Source Current Error-Amplifier Sink Current VSENSE = VOUT - 10% VSENSE = VOUT + 10% 8V ≤ VIN ≤ 40V 1V ≤ VC ≤ 4V Tj = +25°C Tj = +25°C Tj = +25°C Tj = +25°C 3000 100 0.6 Tj ≤ +125°C Tj = +25°C VIN = ≤ 25V, VSW = 0V VIN = 40V, VSW = 0V VIN ≤ 40V, VSENSE = 5.5V Normal Mode Start-Up Mode (Note 4) Tj ≥ 0°C Tj < 0°C 5.5 85 90 85 20 0.03 2000 5000 140 1.0 9000 225 1.7 0.10 %/V V/V µmho µA mA Tj ≥ 0°C Tj < 0°C Tj ≥ 0°C Tj < 0°C Tj = +25°C Tj = +25°C 5 10 8.5 7.3 3.5 3.5 6.5 90 100 CONDITIONS MIN 8.0 TYP MAX 40.0 1.85 2.10 2.30 2.50 300 500 11 8.0 4.8 5.0 8.5 110 120 kHz A % V µA mA V UNI.