Texas Instruments PT7751A, PT7751C, PT7751N, PT7756A, PT7756C Datasheet

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P T 7 7 5 0 S e r i e s

Revised 1/12/99

Application Notes

15 AMP 24V INPUT “BIG-HAMMER III” Mechanical Outline

PROGRAMMABLE ISR

Product Selector Guide

The PT7750 series is a new +24V input, 15 Amp output, high-perfor- mance Integrated Switching Regulator (ISR) housed in a 27-pin SIP package. The 15A capability allows easy integration of the latest high-speed, low-voltage µPs and bus drivers into +24V distributed power systems.

The PT7750 series has been designed to work in parallel with one or

more of the PT7747 current boosters for increased Iout in increments of 15A.

The output voltage of the PT7750 series can be easily programmed over a wide range with a 5-bit input. A differential remote sense is provided which automatically compensates for any voltage drop from the ISR to the load.

2000µF of output capacitance is required for proper operation.

Pin-Out Information

Features

Standard Application

PROGRAMMING PINS

VID0

VID1

REMOTE SENSE (+)

VID2

VID3

VID4

6

4

3

2

1

26

V

IN

L1

PT7750

V

OUT

7 - 11

20

- 25

1µH

	+	27	13 - 19	5	12		+
C						C		LOAD
	IN						OUT
SYNC OUT
GND								GND
STBY*						REMOTE SENSE (-)

Cin = Required 560µF electrolytic (See input filter note)

Cout = Required 2000µF electrolytic L1 = Optional 1µH input choke

Specifications

	Pin	Function		Pin	Function	• +24V bus input
	1	VID0	14		GND	• High Efficiency
	2	VID1		15	GND	• Differential Remote
				16	GND
	3	VID2				Sense
	4	VID3		17	GND
						• 27-pin SIP Package
	5	STBY* - Stand-by		18	GND
						• Parallelable with
				19	GND
	6	VID4
						PT7747 15A current boosters
	7	Vin	20		Vout
	8	Vin		21	Vout
				22	Vout
	9	Vin
	10	Vin		23	Vout
	11	Vin		24	Vout
				25	Vout
	12	Remote Sense Gnd
	13	GND		26	Remote Sense Vout
	For STBY* pin:		27		Sync Out
	open = output enabled
	ground = output disabled.

Characteristics					PT7750 SERIES
(Ta = 25°C unless noted)	Symbols	Conditions			Min	Typ	Max		Units
Output Current	Io	Ta = +60°C, 200 LFM			0.1*	—	15**		A
		Ta = +25°C, natural convection			0.1*	—	15**		A
Input Voltage Range	Vin	0.1A ≤ Io ≤ Io max			20.0	—	28.0		V
Undervoltage Lockout Threshold	Vuvl	0.1A ≤ Io ≤ Io max			—	18.7	—		V
Output Voltage Tolerance	Vo	Vin	= +24V, Io = 15A	PT7751	—	—	±80		mV
		0°C	≤ Ta ≤ +55°C	PT7756	—	—	±160		mV
Line Regulation	Regline	20V ≤ Vin ≤ 28V, Io = Io max (w/remote sense)			—	±15	—		mV
Load Regulation	Regload	Vin = +24V, 0.1 ≤ Io ≤ Io max (w/remote sense)			—	±10	—		mV
Vo Ripple/Noise	Vn	Vin = +24V, Io = Io max			—	75	—		mV
Transient Response	ttr	Io step between 7.5A and 15A			—	100	—		µSec
with Cout = 2000µF	Vos	Vo over/undershoot			—	200	—		mV
Efficiency	η	Vin = +24V, Io = 10A		Vo = 5.0V	—	88	—	%
				Vo = 3.3V	—	84	—	%
				Vo = 2.5V	—	80	—	%
Switching Frequency	ƒo	20V ≤ Vin ≤ 28V			300	350	400		kHz
		0.1A ≤ Io ≤ 15A
Absolute Maximum	Ta				0	—	+85		°C
Operating Temperature Range
Recommended Operating	Ta	Forced Air Flow = 200 LFM			0	—	+65***		°C
Temperature Range		At Vin = +24V, Io = 12A
Storage Temperature	Ts	—			-40	—	+125		°C
Weight	—	Vertical/Horizontal			—	53/66	—		grams

*ISR-will operate down to no load with reduced specifications. Please note that this product is not short-circuit protected.

**The PT7750 series can be easily paralleled with one or more of the PT7747 Current Boosters to provide increased output current in increments of 15A.

***See safe operating area chart.

Output Capacitors: The PT7750 series requires a minimum output capacitance of 2000µF for proper operation. Do not use Oscon type capacitors. The maximum allowable output capacitance is (42,000 ÷ Vout)µF for the PT7751, (96,000 ÷ Vout)µF for the PT7756, or 15,000µF, whichever is less.

Input Filter: An input inductor is optional for most applications. The input inductor must be sized to handle 9ADC with a typical value of 1µH. The input capacitance must be rated for a minimum of 8.0 Arms of ripple current when operated at maximum output current and maximum output voltage. Contact an applications engineer for input capacitor selection for applications at other output voltages and output currents.

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