
For technical support and more information, see inside back cover or visit www.ti.com/powertrends
Standard Application
Cin = Required 2400F electrolytic
Cout = Required 2400F electrolytic
L1
= Optional 1H input choke
32 Amp “Sledge Hammer”
Programmable ISR
PT7771—5V
The PT7771 is a high-output Inte-
grated Switching Regulator (ISR)
housed in a 27-pin SIP package. The
PT7771 operates off a standard 5V bus
to provide a 32 amp low-voltage power
source for the industry’s latest high-
speed Ps, ASICs, DSPs.
The PT7771 has been designed to
work in parallel with one or more of
the PT7746 -32A current boosters to
increase the load current capability in
increments of 32A.
The output voltage is program-
mable from 1.3V to 3.5V via a 5-bit
input, compatible with Intel’s Pentium
Pro Processor. A differential remote
sense is also provided to compensate
for voltage drop between the ISR and
load.
An output capacitance of 2400F is
required for proper operation.
Note that this product does not
include short circuit protection.
For STBY* pin; open = output enabled;
ground = output disabled.
Pin-Out Information
PT7770
7 - 11
13 - 19
20 - 25
27
V
IN
GND
1H
GND
V
OUT
C
OUT
+
C
IN
+
12
26
1
L1
SYNC OUT
LOAD
REMOTE SENSE (+)
REMOTE SENSE (-)
VID1
VID2
VID3
VID4
PROGRAMMING PINS
2
3
4
STBY*
5
6
VID0
Pin
Function
1 VID0
2 VID1
3 VID2
4 VID3
5 STBY*- Stand-by
6 VID4
7 V
in
8 V
in
9 V
in
10 V
in
11 V
in
12 Remote Sense Gnd
13 GND
Pin
Function
14 GND
15 GND
16 GND
17 GND
18 GND
19 GND
20 Vout
21 Vout
22 Vout
23 Vout
24 Vout
25 Vout
26 Remote Sense Vout
27 Sync Out
SLTS054A
(Revised 6/30/2000)
Specifications
Characteristics
PT7771
(T
a = 25°C unless noted)
Symbols
Conditions
Min
Typ
Max
Units
Output Current
Io
Ta = +60°C, 200 LFM, pkg N
0.1 (1)
—32
A
Ta = +25°C, natural convection
0.1 (1)
—26
A
Input Voltage Range
Vin
0.1A
≤ Io ≤ 32A
4.5 (2)
—
5.5
V
Output Voltage Tolerance
Vo
Vin = +5V, Io = 32A
Vo-0.03
—
Vo+0.03
V
0°C
≤ Ta ≤ +55°C
Line Regulation
Regline
4.5V
≤ Vin ≤ 5.5V, Io = 32A
—
±10
—
mV
Load Regulation
Regload
Vin = +5V, 0.1 ≤ Io ≤ 32A
—
±10
—
mV
Vo Ripple/Noise pk-pk
Vn
Vin = +5V, Io = 32A
—
50
—
mV
Transient Response
ttr
Io step between 16A and 32A
—
100
—
Sec
with Cout = 2400F
Vos
Vo over/undershoot
—
200
—
mV
Efficiency
η
Vin = +5V, Io = 20A, Vo = 3.3V
—
90
—
%
Switching Frequency
o
4.5V
≤ Vin ≤ 5.5V
650
700
750
kHz
0.1A
≤ Io ≤ 32A
Absolute Maximum
Ta
Over Vin Range
0
—
+85 (3)
°C
Operating Temperature Range
Storage Temperature
Ts
—
-40
—
+125
°C
Weight
—
Vertical/Horizontal
—
53/66
—
grams
Notes: (1) ISR-will operate down to no load with reduced specifications. Please note that this product is not short-circuit protected.
(2) The minimum input voltage is 4.5V or Vout +1.2V, whichever is greater.
(3) Consult the SOA curves or contact the factory for the appropriate derating.
Output Capacitors: The PT7771 regulator requires a minimum output capacitance of 2400F for proper operation. Do not use Oscon type capacitors.
The maximum allowable output capacitance is 30,000F.
Input Filter: An input filter is optional for most applications. The input inductor must be sized to handle 32ADC with a typical value of 1H.
The input capacitance must be rated for a minimum of 2.6Arms of ripple current. For transient or dynamic load applications, additional
capacitance may be required.