US2076
4-1
Rev. 1.3
4/26/98
PWM SWITCHER CONTROLLER & 7.5A
ADJUSTABLE LOW DROPOUT REGULATOR COMBO
TYPICAL APPLICATION
TYPICAL APPLICATION
Typical application of US2076 in a flexible motherboard designed for Intel
P55
TM
,P54
TM
, AMD K5 & K6
TM
as well as Cyrix M1
TM
and M2
TM
applications.
Tj (C) 7 PIN PLASTIC 7 PIN PLASTIC
TO220 (T) TO263 (M)
0 TO 125 US2076CT US2076CM
DESCRIPTION
DESCRIPTION
The US2076 is a dual function IC combining a
switching controller and a 7.5A adjustable low
dropout regulator all in a compact 7 pin TO220 and
TO263 surface mount packages providing a total so-
lution for dual supply processor applications such as
an Intel P55C
TM
, AMD K6
TM
, as well as Cyrix 6X86L
TM
and the M2
TM
processors. Typically in these applications
a dual supply regulator converts 5V to 3.3V for I/O sup-
ply and a jumper programmable supply of 1.25V to 3.5V
for CORE supply.The linear regulator portion in the
US2076 is an adjustable one that can be programmed
to 3.30V output and has a minimum of 7.5A current ca-
pability designed to provide ample current for most ap-
plications. The US2076 uses an internal regulator gen-
erated from the 12V supply to power the switching con-
troller as well as the 12V supply to drive the power
MOSFET, allowing a low cost N channel MOSFET
switch to be used. The IC also includes an error com-
parator for fast transient response, a precise voltage ref-
erence for setting the output voltage as well as a direct
drive of the MOSFET for the minimum part count.
FEATURES
FEATURES
The US2076 eliminates the need for a
seperate switching controller IC
Minimum part count allows lower system cost
Adjustable 7.5A LDO on board
1.1V Dropout at 7.5A
On board MOSFET driver
Fastest transient response of any controller
method. ( 0 to 100% Duty Cycle in 100 nS )
1% internal voltage reference
Internal Thermal shutdown
Internal Under Voltage Lockout protects
MOSFET during start-up
APPLICATIONS
APPLICATIONS
Dual supply low voltage processor applications,
such as: P55C
TM
,CYRIX M2
TM
, POWER PC
TM
and
AMD K6
TM
PATENT PENDING
PRELIMINARY DATASHEET
Notes: P54C,P55C are trade marks of Intel Corp. K5 & K6 are trade marks of AMD corp. Cyrix 6X86L,M1,M2 are trade marks of Cyrix
Corp. Power PC is trade mark of IBM Corp.
PACKAGE ORDER INFORMATION
PACKAGE ORDER INFORMATION
2076app1-1.2
12V
5V
C1
L1
R1
Q2
D1
C3
C2
C7
L2
C6
R4
R7
R6
D2
CPU
I / O
Vcc2 Det
Core
R8
5V
R5
US2076
Drv
V12
Vfb1
Gnd
Vfb2
Vout
Vin
1
2
3
4
5
6
7
US2076
4-2
Rev. 1.3
4/26/98
ABSOLUTE MAXIMUM RATINGS
ABSOLUTE MAXIMUM RATINGS
12V Supply Voltage ............................................................. 14V
Vin Supply Voltage .............................................................. 7V
LDO Power Dissipation .................................... Internally Limited
FB Pin Voltage........................................................ -0.3V to 5V
Storage Temperature Range ................................. -65 TO 150
C
Operating Junction Temperature ............................... 0 TO 150
C
PACKAGE INFORMATION
PACKAGE INFORMATION
7 PIN PLASTIC TO220 (T)
7 PIN PLASTIC TO263 (M)
JT
=2.7
C/W
JA
=60
C/W
JA
=35
C/W for 1" Square pad
LDO Section
PARAMETER
SYM
TEST CONDITION
MIN TYP MAX UNITS
F.B Voltage Initial Accuracy
Vfb2
Tj=25
C
1.237
1.250
1.262
V
F.B Voltage Total Variation
Vfb2
1.225
1.250
1.275
V
F.B Input Bias Current
Ifb2
Vfb2=1.25V
-1
+1
uA
Dropout Voltage (note 2)
Vout=1.25V, Io=7.5A
1.1
V
Line Regulation
Vout=1.25V,Io=10mA, 3<Vin<6V
0.2
%
Load Regulation (note 1)
Vout=1.25V, 10mA<Io<7.5A
0.5
%
Thermal Regulation
30 mS Pulse
0.01
%/W
Minimum Load Current (note 3)
10
mA
Ripple Rejection
f=120HZ ,Co=25uF Tan,Io=1A 70 dB
V12 Supply Current
Icc2
Vfb2=1V, Vfb1=1.5V, Io=7.5A
75
mA
Switching Controller Section
PARAMETER
SYM TEST CONDITION
MIN TYP MAX UNITS
F.B Voltage Initial Accuracy
Vfb1
Tj=25
C
1.237
1.250
1.262
V
F.B Voltage Total Variation
Vfb1
1.225
1.250
1.275
V
F.B Input Bias Current
Ifb1
Vfb1=1.25V
-1
+1
uA
Min On Time
Vfb1 is sq wave with 300 ns on
800
nS
time and 2 uS off time
Min Off Time
Vfb1 is sq wave with 300 ns off
800
nS
time and 2 uS on time
V12 Supply Current
Icc1
Vfb1=1V, Vfb2=1.5V
10
mA
Maximum Duty Cycle
Dmax
Vfb1=1V
100
%
Minimum Duty Cycle
Dmin
Vfb1=1.5V
0
%
Gate Drive Rise/Fall Time
Vgate
Load=IRL3303
70
nS
F.B Hysterises
12
mV
ELECTRICAL SPECIFICATIONS
ELECTRICAL SPECIFICATIONS
Unless otherwise specified the following specification applies over,Vin=5V,V12=12V,and Tj=0 to 125
C.Low duty
cycle pulse testing are used which keeps junction and case temperatures equal to the ambient temperature.
FRONT VIEW
1
2
3
4
5
6
7
Drv
V12
Vfb1
Gnd
Vfb2
Vout
Vin
FRONT VIEW
1
2
3
4
5
6
7
Drv
V12
Vfb1
Gnd
Vfb2
Vout
Vin
US2076
4-3
Rev. 1.3
4/26/98
PIN DESCRIPTIONS
PIN DESCRIPTIONS
PIN # PIN SYMBOL
PIN DESCRIPTION
3
Vfb1
A resistor divider from this pin to the output of the switching regulator and
ground sets the Core supply voltage.
6
Vout
The output of the linear regulator. A minimum of a 100uF low ESR capacitor must be
connected from this pin to ground to insure stability.
7
Vin
The input pin of the linear regulator. Typically a large storage capacitor is connected
from this pin to ground to insure that the input voltage does not sag below the minimum
drop out voltage during the load transient response. This pin must always be higher than
Vout plus the maximum dropout voltage in order for the device to regulate properly.
4
Gnd
This pin is connected to the IC substrate and must be connected to the lowest
potential in the system. It is also connected to the Tab of the package.
1
Drv
The PWM output of the switching controller. This pin is a totem pole drive that is
connected to the gate of the power MOSFET. A resistor may be placed in series from
this pin to the gate in order to reduce switching noise.
5
Vfb2
A resistor divider from this pin to the output of the linear regulator and
ground sets the I/O supply voltage.
2
V12
This pin is connected to the 12V supply voltage. A high frequency cap must be
connected from this pin to the GND pin of the IC.
BLOCK DIAGRAM
BLOCK DIAGRAM
Figure 1 - Simplified block diagram of the US2076
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.
Vref
UVLO
1.25V
PWM Control
V12
Vout
Drv
Gnd
Vfb 1
Vin
4
1
2
3
6
7
2076blk1-1.1
Vfb2
5
5V Reg
US2076
4-4
Rev. 1.3
4/26/98
TYPICAL APPLICATION
TYPICAL APPLICATION
Figure2- Typical application of US2076 in a flexible motherboard with the 4 bit VID output voltage selection. This circuit
uses a single jumper that programs the output voltage in 16 steps with 0.1V steps from 2V to 3.5V, designed for Intel P55
TM
,P54
TM
,
AMD K5 & K6
TM
as well as Cyrix M1
TM
and M2
TM
applications. The Vcc2Det pin automatically shuts down the I/O when a single plane
processor is dropped in the socket.
Ref Desig
Description Qty
Part #
Manufacturer
U1
LDO/Switcher IC
1
US2076CT (TO220)
Unisem
US2076CM (TO263) (note 1)
Q1
MOSFET
1
IRL3303 (TO220)
International
IRL3103S (TO263) (note 1)
Rectifier
D1
Schottky Diode
1
MBR1045CT (TO220)
Motorola
MBRB1545CT (TO263) (note1)
D2
Diode, GP
1
1N4148
L2
Inductor
1
Core:T50-18,L=4 uH
Micro Metal
Turns: 10T, 18 AWG
(core)
L1
Inductor
1
L=2 uH
R1
Resistor
1
22 ohm,5%, SMT 1206 size
R2
Resistor
1
10 ohm, 5%, SMT 1206 size
R4A
Resistor
1
806 ohm,1%, SMT 0805 size
R4B
Resistor
1
90.9 kohm,1%, SMT 0805 size
R5A
Resistor
1
1.24 kohm,1%, SMT 0805 size
R5B
Resistor
1
2.49 kohm,1%, SMT 0805 size
R5C
Resistor
1
4.99 kohm,1%, SMT 0805 size
R5D
Resistor
1
10 kohm,1%, SMT 0805 size
R5E
Resistor
1
1.30 kohm,1%, SMT 0805 size
R6
Resistor
1
ohm,1%, SMT 0805 size
R7
Resistor
1
ohm,1%, SMT 0805 size
R8
Resistor
1
10 kohm,5%, SMT 0805 size
C3
Capacitor
1
1 uF,Ceramic, SMT 0805 size, Z5U
C1
Capacitor
1
EEUFA1A681L, 680uF,10V, Elect
Panasonic
C4
Capacitor
1
470pF,Ceramic, SMT 0805 size
C2
Capacitor
1
6MV1500GX, 1500uF,6.3V, Elect
Sanyo
C6
Capacitor
1
EEUFA1A681L, 680uF,10V, Elect
Panasonic
C7
Capacitor
4
6MV1500GX, 1500uF,6.3V, Elect
Sanyo
HS1
Heat Sink
1
For MOSFET , 577002
Aavid
HS2
Heat Sink
1
For Schottky Diode , 577002
Aavid
HS3
Heat Sink
1
For US2076 , 507222 (I/O Load Current<5A)
Aavid
576602 (I/O Load Current< 3.5A)
Note 1: For the applications where it is desirable to eliminate the heat sink, the US2076CM for U1 when load current is
less than 1.5A, the IRL3103S for Q2 and MBR1545CT for D1 in TO263 packages with minimum of 1" square copper pad
can be used.
U1
1
2076app2-1.2
12V
5V
C1
L1
R1
Q2
D1
C3
R2
C4
C2
R5A
R5B
R5C
R5D
R5E
C7
L2
C6
R4A
Drv
V12
Vfb1
Gnd
Vfb2
Vout
Vin
1
2
3
4
5
6
7
R7
R6
2
3
4
5
6
7
8
JP1
D2
CPU
I / O
Vcc2 Det
Core
R8
5V
R4B
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