US2076
PWM SWITCHER CONTROLLER & 7.5A
ADJUSTABLE LOW DROPOUT REGULATOR COMBO
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
DESCRIPTION
PATENT PENDING
PRELIMINARY DATASHEET
APPLICATIONS
Dual supply low voltage processor applications,
such as: P55C™,CYRIX M2™, POWER PC™ and
AMD K6™
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
™,
AMD K6™, as well as Cyrix 6X86L™
and the M2™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.
TYPICAL APPLICATION
L1
5V
C1
Vin
Vout
Vfb2
C6
R6
5V
R7
D2
R8
I/O
US2076
Gnd
Vfb1
V12
Drv
7
6
5
4
3
2
1
CPU
Vcc2 Det
L2
R1
Q2
R4
C2
C7
Core
2076app1-1.2
12V
C3
D1
R5
Typical application of US2076 in a flexible motherboard designed for Intel
P55™,P54™, AMD K5 & K6™ as well as Cyrix M1™ and M2™ applications.
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
Tj (°C)
0 TO 125
Rev. 1.3
4/26/98
7 PIN PLASTIC
TO220 (T)
US2076CT
7 PIN PLASTIC
TO263 (M)
US2076CM
4-1
US2076
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
7 PIN PLASTIC TO220 (T)
FRONT VIEW
7
6
5
4
3
2
1
7 PIN PLASTIC TO263 (M)
FRONT VIEW
7
6
5
4
3
2
1
Vin
Vout
Vfb2
Gnd
Vfb1
V12
Drv
Vin
Vout
Vfb2
Gnd
Vfb1
V12
Drv
θ
JT
=2.7°C/W
θ
JA
=60°C/W
θ
JA
=35°C/W for 1" Square pad
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.
LDO Section
PARAMETER
SYM
F.B Voltage Initial Accuracy
Vfb2
F.B Voltage Total Variation
Vfb2
F.B Input Bias Current
Ifb2
Dropout Voltage (note 2)
Line Regulation
Load Regulation (note 1)
Thermal Regulation
Minimum Load Current (note 3)
Ripple Rejection
V12 Supply Current
Icc2
Switching Controller Section
PARAMETER
F.B Voltage Initial Accuracy
F.B Voltage Total Variation
F.B Input Bias Current
Min On Time
Min Off Time
V12 Supply Current
Maximum Duty Cycle
Minimum Duty Cycle
Gate Drive Rise/Fall Time
F.B Hysterises
Icc1
Dmax
Dmin
Vgate
TEST CONDITION
Tj=25°C
Vfb2=1.25V
Vout=1.25V, Io=7.5A
Vout=1.25V,Io=10mA, 3<Vin<6V
Vout=1.25V, 10mA<Io<7.5A
30 mS Pulse
f=120HZ ,Co=25uF Tan,Io=1A
Vfb2=1V, Vfb1=1.5V, Io=7.5A
MIN TYP
1.237 1.250
1.225 1.250
-1
1.1
0.2
0.5
0.01
70
75
MAX
1.262
1.275
+1
UNITS
V
V
uA
V
%
%
%/W
mA
dB
mA
10
SYM
Vfb1
Vfb1
Ifb1
TEST CONDITION
Tj=25°C
Vfb1=1.25V
Vfb1 is sq wave with 300 ns on
time and 2 uS off time
Vfb1 is sq wave with 300 ns off
time and 2 uS on time
Vfb1=1V, Vfb2=1.5V
Vfb1=1V
Vfb1=1.5V
Load=IRL3303
MIN
1.237
1.225
-1
TYP
1.250
1.250
800
800
10
MAX
1.262
1.275
+1
UNITS
V
V
uA
nS
nS
mA
%
%
nS
mV
100
0
70
12
4-2
Rev. 1.3
4/26/98
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.
PIN DESCRIPTIONS
PIN #
3
6
7
PIN SYMBOL
Vfb1
Vout
Vin
PIN DESCRIPTION
A resistor divider from this pin to the output of the switching regulator and
ground sets the Core supply voltage.
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.
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.
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.
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.
A resistor divider from this pin to the output of the linear regulator and
ground sets the I/O supply voltage.
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.
4
1
Gnd
Drv
5
2
Vfb2
V12
BLOCK DIAGRAM
V12
2
Vfb 1
3
Vin
7
Vout
6
Drv
1
UVLO
Vref
PWM Control
5V Reg
Gnd
4
1.25V
2076blk1-1.1
Vfb2
5
Figure 1 - Simplified block diagram of the US2076
Rev. 1.3
4/26/98
4-3
US2076
TYPICAL APPLICATION
5V
C1
Vin
Vout
Vfb2
C6
R6
5V
R7
D2
Vcc2 Det
L2
R1
Q2
R4A
R4B
C2
C7
Core
R8
L1
I/O
7
6
U1
5
Gnd
4
3
2
1
V12
Drv
CPU
Vfb1
2076app2-1.2
12V
C3
C4
R2
D1
R5A
JP1 1
2
R5B
3
4
R5C
5
6
R5D
7
8
R5E
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™,P54™,
AMD K5 & K6™ as well as Cyrix M1™ and M2™ applications. The Vcc2Det pin automatically shuts down the I/O when a single plane
processor is dropped in the socket.
Ref Desig
U1
Q1
D1
D2
L2
L1
R1
R2
R4A
R4B
R5A
R5B
R5C
R5D
R5E
R6
R7
R8
C3
C1
C4
C2
C6
C7
HS1
HS2
HS3
Description
LDO/Switcher IC
MOSFET
Schottky Diode
Diode, GP
Inductor
Inductor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Capacitor
Capacitor
Capacitor
Capacitor
Capacitor
Capacitor
Heat Sink
Heat Sink
Heat Sink
Qty
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
4
1
1
1
Part #
US2076CT (TO220)
US2076CM (TO263) (note 1)
IRL3303 (TO220)
IRL3103S (TO263) (note 1)
MBR1045CT (TO220)
MBRB1545CT (TO263) (note1)
1N4148
Core:T50-18,L=4 uH
Turns: 10T, 18 AWG
L=2 uH
22 ohm,5%, SMT 1206 size
10 ohm, 5%, SMT 1206 size
806 ohm,1%, SMT 0805 size
90.9 kohm,1%, SMT 0805 size
1.24 kohm,1%, SMT 0805 size
2.49 kohm,1%, SMT 0805 size
4.99 kohm,1%, SMT 0805 size
10 kohm,1%, SMT 0805 size
1.30 kohm,1%, SMT 0805 size
ohm,1%, SMT 0805 size
ohm,1%, SMT 0805 size
10 kohm,5%, SMT 0805 size
1 uF,Ceramic, SMT 0805 size, Z5U
EEUFA1A681L, 680uF,10V, Elect
470pF,Ceramic, SMT 0805 size
6MV1500GX, 1500uF,6.3V, Elect
EEUFA1A681L, 680uF,10V, Elect
6MV1500GX, 1500uF,6.3V, Elect
For MOSFET , 577002
For Schottky Diode , 577002
For US2076 , 507222 (I/O Load Current<5A)
576602 (I/O Load Current< 3.5A)
Manufacturer
Unisem
International
Rectifier
Motorola
Micro Metal
(core)
Panasonic
Sanyo
Panasonic
Sanyo
Aavid
Aavid
Aavid
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.
4-4
Rev. 1.3
4/26/98
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