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UNISEM |
US1261
DUAL 6A AND 1A LOW DROPOUT
POSITIVE FIXED OUTPUT REGULATOR
FEATURES
Guaranteed to provide 1.5V and 2.5V Sup-
plies with 3.1V input.
Fast Transient Response
1% Voltage Reference Initial Accuracy
Built in Thermal Shutdown
APPLICATIONS
Pentium II Processor Applications
DESCRIPTION
The US1261 product using a proprietary process com-
bines a dual low dropout regulators with fixed outputs of
1.5V and 2.5V in a single package with the 1.5V out-
put having a minimum of 6A and the 2.5V having a 1A
output current capability. This product is specifically de-
signed to provide well regulated supplies from 3.3V to
generate 1.5V for GTL+ termination resistor supply
and 2.5V clock supply for the new generation of
the Pentium II processor applications.
TYPICAL APPLICATION
1261app1-1.3
3.3V
C1
Vout1 5
US1261
Vin 4
Gnd 3
Vout2 2
Vctrl 1
5V
R1
C2
2.5V / 1A
C3
1.5V / 6A
C4
Typical application of US1261 in a Pentium II processor application
PACKAGE ORDER INFORMATION
Tj (°C)
0 TO 150
5 PIN PLASTIC
TO220(T)
US1261CT
5 PIN PLASTIC
TO263(M)
US1261CM
5 PIN PLASTIC
POWER FLEX(P)
US1261CP
Rev. 1.7
3/22/99
3-1
US1261
ABSOLUTE MAXIMUM RATINGS
Input Voltage (Vin) ............................................................. 10V
Power Dissipation ............................................ Internally Limited
Storage Temperature Range ................................ -65°C TO 150°C
Operating Junction Temperature Range ...................... 0°C TO 150°C
PACKAGE INFORMATION
7 PIN PLASTIC TO220
7 PIN PLASTIC TO263
FRONT VIEW
5
4
3
2
1
Vout1
Vin
Gnd
Vout2
Vctrl
FRONT VIEW
5
4
3
2
1
Vout1
Vin
Gnd
Vout2
Vctrl
θJT =2.7°C/W θJA =60°C/W θJA =30°C/W for 1"sq pad
7 PIN POWER FLEX (P)
FRONT VIEW
5
4
3
2
1
Vout1
Vin
Gnd
Vout2
Vctrl
θJA =30°C/W for 1"sq pad
ELECTRICAL SPECIFICATIONS
Unless otherwise specified ,these specifications apply over ,Cin=1 uF,Cout=100uF,and Tj=0 to 150°C.Typical
values refer to Tj=25°C. Ifl=6A for output #2 & 1A for output #1.Vctrl=5V,Vin=3.3V.
PARAMETER
SYM TEST CONDITION
MIN TYP MAX UNITS
Vctrl Input Voltage
3.0 V
Output Voltage #2
Vo2 Io=10mA, Tj=25°C
1.485 1.500 1.515
V
Io=10mA
1.470 1.500 1.530
Output Voltage #1
Vo1 Io=10mA, Tj=25°C
2.462 2.500 2.537
V
Io=10mA
2.425 2.500 2.575
Line Regulation
Io=10mA, 3.1V<Vin<3.6V
0.2 %
Load Regulation (note 1)
10mA<Io<Ifl
0.4 %
Dropout Voltage (output #2)
Note 2,
Io=6A, Vctrl=4.75V
1.3 V
Dropout Voltage (output #1)
Note 2,
Io=1A, Vctrl=4.75V
0.4 0.6
V
Current Limit (output #2)
dVo=100mV
6.1
A
Current Limit (output #1)
dVo=100mV
1.1
A
Minimum Load Current
5 10 mA
(note 3)
Thermal Regulation
30 mS PULSE,Io=Ifl
0.01 0.02 %/W
Ripple Rejection
f=120HZ ,Co=25uF Tan
Io=0.5*Ifl
70 dB
Temperature Stability
Io=10mA
0.5 %
Long Term Stability
Tj=125°C,1000 Hrs
0.3 %
RMS Output Noise
10hz<f<10khz
0.003
%Vo
Note 1 : Low duty cycle pulse testing with Kelvin con-
nections are required in order to maintain accurate data.
Note 2 : Drop-out voltage is defined as the minimum
differential voltage between Vin and Vout required to main-
tain regulation at Vout. It is measured when the output
voltage drops 1% below its nominal value.
Note 3 : Minimum load current is defined as the mini-
mum current required at the output in order for the out-
put voltage to maintain regulation. Typically the resistor
dividers are selected such that it automatically main-
tains this current.
3-2
Rev. 1.7
3/22/99
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