19-0182; Rev 3; 9/95 5V/3.3V/3V 5A Step-Down, PWM, Switch-Mode DC-DC Regulators 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. _______________________Applications Distributed Power from High-Voltage Buses High-Current, High-Voltage Step-Down Multiple-Output Buck Converter ___________________________Features ♦ Input Range: Up to 40V ♦ 5A On-Chip Power Switch ♦ Fixed Outputs: 5V (MAX787) 3.3V (MAX788) 3V (MAX789) ♦ 100kHz Switching Frequency ♦ Excellent Dynamic Characteristics ♦ Few External Components ♦ 8.5mA Quiescent Current ♦ TO-220 Package ______________Ordering Information PART TEMP. RANGE PIN-PACKAGE MAX787CCK 0°C to +70°C 5 TO-220 MAX787ECK -40°C to +85°C 5 TO-220 MAX788CCK 0°C to +70°C 5 TO-220 MAX788ECK -40°C to +85°C 5 TO-220 MAX789CCK 0°C to +70°C 5 TO-220 MAX789ECK -40°C to +85°C 5 TO-220 ___________Product Selection Guide __________Typical Operating Circuit INPUT 8V TO 40V 50µH VIN VSW OUTPUT 5V AT 5A 220µF MAX787 VC MBR745 SENSE 2.7k GND 0.01µF PART VOUT (V) MAX724 Adjustable IOUT MAX (A) 5 MAX726 Adjustable 2 MAX727 5 2 MAX728 3.3 2 MAX729 3 2 MAX787 5 5 MAX788 3.3 5 MAX789 3 5 __________________Pin Configuration FRONT VIEW 470µF MAX787 MAX788 MAX789 5 4 VIN 3 2 GND 1 SENSE VSW VC 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 Call toll free 1-800-998-8800 for free samples or literature. 1 MAX787/MAX788/MAX789 _______________General Description MAX787/MAX788/MAX789 5V/3.3V/3V 5A Step-Down, PWM, Switch-Mode DC-DC Regulators 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 CONDITIONS MIN Input Supply Voltage Range 8.0 ISW = 1A Switch-On Voltage (Note 1) ISW = 5A Switch-Off Leakage Supply Current (Note 3) Minimum Supply Voltage TYP MAX UNITS 40.0 V Tj ≥ 0°C 1.85 Tj < 0°C 2.10 Tj ≥ 0°C 2.30 Tj < 0°C 2.50 VIN = ≤ 25V, VSW = 0V Tj = +25°C 5 300 VIN = 40V, VSW = 0V Tj = +25°C 10 500 VIN ≤ 40V, VSENSE = 5.5V 8.5 11 Normal Mode 7.3 8.0 Tj ≥ 0°C 3.5 4.8 Tj < 0°C 3.5 5.0 5.5 85 6.5 90 8.5 Tj = +25°C 90 100 Tj ≤ +125°C 85 Start-Up Mode (Note 4) Switch-Current Limit (Note 5) Maximum Duty Cycle Switching Frequency VOUT = VSENSE = 0V (Note 5) Switching Frequency Line Regulation 8V ≤ VIN ≤ 40V Error-Amplifier Voltage Gain 1V ≤ VC ≤ 4V Error-Amplifier Transconductance V Tj = +25°C 20 Tj = +25°C 2000 0.03 µA mA V A % 110 120 kHz 0.10 %/V µmho V/V Tj = +25°C 3000 5000 9000 Error-Amplifier Source Current VSENSE = VOUT - 10% Tj = +25°C 100 140 225 µA Error-Amplifier Sink Current VSENSE = VOUT + 10% Tj = +25°C 0.6 1.0 1.7 mA 2 _______________________________________________________________________________________ 5V/3.3V/3V 5A Step-Down, PWM, Switch-Mode DC-DC Regulators MAX787/MAX788/MAX789 ELECTRICAL CHARACTERISTICS (continued) (VIN = 25V, Tj = TMIN to TMAX, unless otherwise noted.) PARAMETER CONDITIONS MAX787 MAX788 MAX789 MAX787 MAX788 MAX789 SENSE Voltage VC = 2V SENSE Pin Divider Resistance Tj = +25°C Output Voltage Tolerance VOUT (nominal) = 5V (MAX787), 3.3V (MAX788), or 3V (MAX789); Tj = +25°C all conditions of input voltage, Tj = TMIN to output voltage, and load TMAX current Output Voltage Line Regulation VC Voltage VC Voltage Temperature Coefficient 8V ≤ VIN ≤ 40V 0% duty cycle 0% duty cycle Tj = +25°C Tj = TMIN to TMAX Thermal Resistance Junction to Case (Note 6) MIN TYP MAX 4.85 3.20 2.90 3.0 2.5 2.2 5.00 3.30 3.00 5.0 4.2 3.8 5.15 3.40 3.10 8.0 7.0 6.5 UNITS ±0.5 ±2.0 ±1.0 ±3.0 0.005 1.5 -4 0.020 %/V V mV/°C 2.5 °C/W V kΩ % Note 1: Do not exceed switch-to-input voltage limitation. Note 2: For switch currents between 1A and 5A, maximum switch-on voltage can be calculated via linear interpolation. Note 3: By setting the SENSE pin to 5.5V, the VC pin is forced to its low clamp level and the switch duty cycle is forced to zero, approximating the zero load condition. Note 4: For proper regulation, total voltage from VIN to GND must be ≥ 8V after start-up. Note 5: To avoid extremely short switch-on times, the switch frequency is internally scaled down when VSENSE is less than 2.6V (MAX787), 2.0V (MAX788), or 1.8V (MAX789). Switch-current limit is tested with VSENSE adjusted to give a 1µs minimum switch-on time. Note 6: Guaranteed, not production tested. ______________________________________________________________Pin Description PIN NAME FUNCTION 1 SENSE 2 VC 3 GND Ground requires a short, low-noise connection to ensure good load regulation. The internal reference is referred to GND, so errors at this pin are multiplied by the error amplifier. 4 VSW Internal Power Switch Output. The Switch output can swing 35V below ground and is rated for 5A. 5 VIN VIN supplies power to the internal circuitry and also connects to the collector of the internal power switch. VIN must be bypassed with a low-ESR capacitor, typically 200µF or 220µF. SENSE Input is the internal error amplifier's input, and should be directly connected to VOUT. SENSE also aids current limiting by reducing oscillator frequency when VOUT is low. Error-Amplifier Output. A series RC network connected to this pin compensates the MAX787/MAX788/ MAX789. Output swing is limited to about 5.8V in the positive direction and -0.7V in the negative direction. VC can also synchronize the MAX787/MAX788/MAX789 to an external TTL clock in the 115kHz to 170kHz range. See MAX724/MAX726 data sheet. _______________________________________________________________________________________ 3 MAX787/MAX788/MAX789 5V/3.3V/3V 5A 2A Step-Down, PWM, Switch-Mode DC-DC Regulators ________________________________________________________Package Information DIM A E F φP Q H1 D L2 J1 A B C1 D E e F H1 J1 J2 J3 L L1 L2 φP Q INCHES MAX MIN 0.190 0.140 0.040 0.015 0.022 0.014 0.650 0.560 0.420 0.380 0.067 BSC 0.055 0.045 0.270 0.230 0.115 0.080 0.185 0.170 0.335 0.327 0.200 0.170 0.340 0.260 0.720 0.700 0.161 0.139 0.120 0.100 MILLIMETERS MIN MAX 3.56 4.82 0.38 1.01 0.41 0.50 14.23 16.51 9.66 10.66 1.70 BSC 1.14 1.39 5.85 6.85 2.04 2.92 4.32 4.70 8.31 8.51 4.32 5.08 6.60 8.64 17.78 18.29 3.54 4.08 2.54 3.04 21-005- L L1 5-PIN TO-220 (STAGGERED LEAD) PACKAGE C1 B J2 e J3 DIM A E F φP Q H1 D J1 A B C1 D E e F H1 J1 L φP Q INCHES MAX MIN 0.190 0.140 0.040 0.015 0.022 0.014 0.650 0.560 0.420 0.380 0.067 BSC 0.055 0.045 0.270 0.230 0.115 0.080 0.580 0.500 0.161 0.139 0.120 0.100 MILLIMETERS MIN MAX 3.56 4.82 0.38 1.01 0.41 0.50 14.23 16.51 9.66 10.66 1.70 BSC 1.14 1.39 5.85 6.85 2.04 2.92 12.70 14.73 3.54 4.08 2.54 3.04 21-4737- L B C1 e 5-PIN TO-220 (STRAIGHT LEAD) PACKAGE CONTACT FACTORY FOR AVAILABILITY Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. 4 ___________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600 © 1995 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.