PT7778—3.3V
32 Amp Programmable Integrated
Switching Regulator
SLTS115
(Revised 8/31/2000)
Description
ble with Intel’s Pentium II Processors.
The 32A capability provides the
ideal power source for the industry’s
latest high-speed, low-voltage µPs,
DSPs, and custom VLSI devices.
For additional current, the PT7778
may be paralleled with up to two
PT7740 32A current boosters.
A differential remote sense is
The PT7778 is a high-output 32A
Integrated Switching Regulator (ISR),
housed in a 27-pin SIP package, The
PT7778 is the 3.3V-input bus version
of the PT7779. It includes short
circuit protection and requires only
330µF of output capacitance for
proper operation.
The output voltage of the PT7778
is programmable from 1.3V to 2.05V
using a 4-bit input, which is compati-
provided to compensate for voltage
drop between the ISR and load.
Pin-Out Information
Standard Application
Pin Function
15 GND
16 GND
Pin Function
1
2
3
4
5
6
7
8
VID0
PROGRAMMING PINS
VID1
REMOTE SENSE (+)
VID0
VID1
VID2
VID3
17 GND
VID2
VID3
18 GND
19 GND
4
VID3
3
-
2
VID0
1
26
STBY*- Stand-by
SNS(+)
N/C
Vin
VOUT
20
21
22
23
24
25
V
V
V
V
V
V
out
out
out
out
out
out
L1
7-11
20-25
Vo
Vin
VIN
PT7778
1µH
Vin
Synch
Out
STBY
5
GND
SNS(-)
+
+
9
Vin
LOAD
27
13-19
12
C IN
COUT
SYNC OUT
G N D
10 Vin
11 Vin
12 Remote Sense Gnd (3)
13 GND
G N D
REMOTE SENSE (–)
26 Remote Sense V
27 Sync Out
out
STBY*
14 GND
C
C
= Required 2400µF electrolytic
Required 330µF electrolytic
in
out
For STBY* pin; open = output enabled;
ground = output disabled.
=
L1 = Optional 1µH input choke
Specifications
PT7778
Characteristics
(T a = 25°C unless noted)
Symbols
Conditions
Min
Typ
Max
Units
(1)
(1)
Output Current
Io
Ta = +60°C, 200 LFM, pkg N
Ta = +25°C, natural convection
0.1
0.1
—
—
32
31
A
V
V
Input Voltage Range
Vin
0.1A ≤ Io ≤ 32A
3.1
—
3.6
Output Voltage Tolerance
∆Vo
Vin = +3.3V, Io = 32A
Vo-0.03
—
Vo+0.03
–40°C ≤ Ta ≤ +85°C
Line Regulation
Regline
Regload
Vn
3.1V ≤ Vin ≤ 3.6V, Io = 32A
Vin = +3.3V, 0.1 ≤ Io ≤ 32A
Vin = +3.3V, Io = 32A
—
—
—
±10
±10
50
—
—
—
mV
mV
mV
Load Regulation
Vo Ripple/Noise pk-pk
Transient Response
with Cout = 330µF
ttr
Io step between 16A and 32A
Vo over/undershoot
—
—
100
200
—
—
µSec
mV
Vos
Efficiency
η
Vin = +3.3V, Io = 20A, Vo = 1.8V
—
90
—
%
Switching Frequency
ƒo
3.1V ≤ Vin ≤ 3.6V
0.1A ≤ Io ≤ 32A
300
350
400
kHz
Absolute Maximum
Ta
Ts
Over Vin Range
–40
-40
—
—
+85 (2)
+125
—
°C
Operating Temperature Range
Storage Temperature
Mechanical Vibration
—
—
°C
Per Mil-STD-883D, Method 2007.2
20-20,000Hz, Soldered in a PC board
10/15
53/66
G’s
Weight
—
Vertical/Horizontal
—
—
grams
Notes: (1) ISR-will operate down to no load with reduced specifications.
(2) Consult the Safe Operating Area curves, or contact the factory for the appropriate derating.
(3) If the remote sense ground is not used, pin 12 must be connected to pin13 for optimum output voltage accuracy.
External Capacitors: The PT7778 requires a minimum output capacitance of 330µF for proper operation. The PT7778 also requires an input capacitance of 2400µF,
which must be rated for a minimum of 2.0Arms of ripple current. For transient or dynamic load applications, additional capacitance may be required. For further infor-
mation, see the accompanying application note on capacitor selection for this product.
Input Filter: An input filter inductor is optional for most applications. The input inductor must be sized to handle 32ADC with a typical value of 1µH.
For technical support and more information, see inside back cover or visit www.ti.com/powertrends