Dual Synchronous Voltage Mode
Controller with Current Sharing Circuitry
POWER MANAGEMENT
Description
The SC1176 is a versatile 2 phase, synchronous, volt-
age mode PWM controller that may be used in two dis-
tinct ways. First, the SC1176 is ideal for applications
where point of use output power exceeds any single in-
put power budget. Alternatively, the SC1176 can be used
as a dual switcher. The SC1176 features a temperature
compensated voltage reference, over current protection
with 50% fold-back and internal level-shifted, high-side
drive circuitry.
In current sharing configuration, the SC1176 can pro-
duce a single output voltage from two separate voltage
sources (which can be different voltage levels) while
maintaining current sharing between the channels. Cur-
rent sharing is programmable to allow loading each input
supply as required by the application.
In dual switcher configuration, two feedback paths are
provided for independent control of the separate out-
puts. The device will provide a regulated output from
flexibly configured inputs (3.3V, 5V, 12V), provided 5V is
present for V
CC
. The two switchers are 180° out of phase
to minimize input and output ripple.
The SC1176A has the phases of the Master and the Slave
inverted.
It offers a different pattern for ripple cancellation and
prevents phase fold back during current limit.
The two chips are pin compatible.
SC1176/SC1176A
Features
300kHz fixed frequency operation
Soft Start and Enable function
Power Good output provided
Over current protection with 50% fold-back
Phase-shifted switchers minimize ripple
High efficiency operation, >90%
Programmable output(s) as low as .9V
Industrial temperature range
SOIC-20 or TSSOP-20 pin Lead free package. This
product is fully WEEE and RoHS compliant
Two Phase, Current Sharing Controller
Flexible, same or separate V
IN
Programmable current sharing
Combined current limit with fold-back
2 phases operating opposed for ripple reduction
Thermal distribution via multi-phase output
Two Independent PWM Controllers
Flexible, same or separate V
IN
Independent control for each channel
Independent and separate current limit
2 phases operating opposed for ripple reduction (if
same V
IN
used)
Applications
Graphics cards
DDR Memory
Peripheral add-in card
SSTL Termination
Dual-Phase power supply
Power supplies requiring two outputs
Revision: June 29, 2006
1
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SC1176/SC1176A
POWER MANAGEMENT
Typical Application Circuit
2 Channels with Current Sharing
2006 Semtech Corp.
2
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SC1176/SC1176A
POWER MANAGEMENT
Absolute Maximum Rating
Exceeding the specifications below may result in permanent damage to the device, or device malfunction. Operation outside of the parameters specified
in the Electrical Characteristics section is not implied.
Parameter
V
CC
to GND
PGND to GND
BST to GND
Thermal Resistance Junction to Case
SOIC
TSSOP
Thermal Resistance Junction to Ambient
SOIC
TSSOP
Operating Ambient Temperature Range
Operating Junction Temperature Range
Storage Temperature Range
Lead Temperature (Soldering) 10 sec
Symbol
V
IN
Limits
-0.3 to 15
±1
-0.3 to 26
Units
V
V
V
°C/W
θ
JC
24
27
65
85
0 to 70
0 to 125
-65 to +150
300
θ
JA
T
A
T
J
T
STG
T
LEAD
°C/W
°C
°C
°C
°C
Electrical Characteristics
Unless Specified: V
CC
= 4.75 to 5.25V, GND = PGND = 0V, FB = V
O
, 0mV < (CS(+) - (CS(-)) < 60mV , T
J
= 25°C
Parameter
Output Voltage
Supply Voltage
Supply Current
Reference Voltage
Reference Voltage Line Regulation
Reference Voltage Load Regulation
Output Line Regulation
Output Load Regulation
Gain (A
OL
)
Current Limit Voltage
Oscillator Frequency
Oscillator Max Duty Cycle
DH Sink Current
DH Sink Current
DH Source Current
DH Source Current
Conditions
I
O
= 2A
(1)
, V
OUT
set to 2.75V
V
CC
V
CC
= 5.0
I
REF
= 0µA
5V < V
CC
< 15V
I
REF
= 0µA to 30µA
5V < V
IN
< 15V
I
O
= 0.3A to 15A
(1)
V
OSENSE
to V
O
Min
2.65
4.2
Typ
2.75
Max
2.85
15
Units
V
V
mA
15
0.89
0.9
0.91
0.5
-12
0.5
1
35
60
270
90
70
300
95
80
330
V
%
mV
%
%
dB
mV
kHz
%
A
A
A
A
DH - PGND = 3.0V
DH - PGND = 2.0V
BSTH - DH = 3.5V
BSTH - DH = 2.5V
1.3
0.85
1.3
0.85
2006 Semtech Corp.
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SC1176/SC1176A
POWER MANAGEMENT
Electrical Characteristics (Cont.)
Unless Specified: V
CC
= 4.75 to 5.25V, GND = PGND = 0V, FB = V
O
, 0mV < (CS(+) - (CS(-)) < 60mV , T
J
= 25°C
PARAMET ER
DL Sink Current
DL Sink Current
DL Source Current
DL Source Current
Dead Time
Soft Start Charge Current
(2)
Soft Start Enable
Soft Start End
Soft Start Transition
(2)
Power Good Window
(3)
Fold Back Current
Fold Back Voltage Knee
Input Bias Current
BSTH to DH Leakage
DH to PGND Leakage
BSTL to DL Leakage
DL to PGND
CONDIT IONS
DL - PGNG = 3.0V
DL - PGND = 2.0V
BSTL - DL = 3.5V
BSTL - DL = 2.5V
Note 5
MIN
1.3
0.85
1.3
0.85
50
T YP
MAX
UNIT S
A
A
A
A
100
25
150
ns
µA
V
V
V
%V
OUT
I
LIM
0% duty cycle
100% duty cycle
Synchronous mode
1.4
2.5
3.3
+10
V
OUT
= 0V
I=
ILIM
50%
0.9
V
OUT
1
10
10
10
10
V
µA
µA
µA
µA
µA
-IN1, +IN2, -IN2
BSTH - DH = 5V
DH - PGND = 5V
BSTL - DL = 5V
DL - PGND = 5V
Notes:
(1) Specification refers to application circuit.
(2) The soft start pin sources 25µA to an external capacitor. The converter operates in synchronous mode above the soft
start transition threshold and in asynchronous mode below it.
(3) Power good is an open collector pulled low when the output voltage is outside the ±10% window.
(4) This device is ESD sensitive. Use of standard ESD handling precautions is required.
(5) 200ns maximum at 75°.
Marking Information
(SOIC-20)
(TSSOP-20)
6
TOP
yyww = Date Code (Example: 9908)
xxxx = Semtech Lot # (Example: 90101)
2006 Semtech Corp.
4
nnnn = Part Number (Example: 1471)
yyww = Date Code (Example: 0012)
xxxxxx = Semtech Lot # (Example: P94A01)
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SC1176/SC1176A
POWER MANAGEMENT
Pin Configuration
Top View
Ordering Information
Device
(1)
SC1176CSWTR
SC1176CSWTRT
SC1176ASWTR
SC1176ASWTRT
SC1176TSTR
SC1176TSTRT
SC1176ATSTR
SC1176EVB-1
SC1176-2EVB-2
Current Share Version Evaluation
Board
Dual Channel Version Evaluation
TSSOP-20
SOIC-20
Package
(2)
(SOIC-20 and TSSOP-20 Pin)
Notes:
(1) Only available in tape and reel packaging. A reel
contains 1000 (SOIC) or 2500 (TSSOP) devices.
(2) Lead free product. This product is fully WEEE and
RoHS compliant.
Pin Descriptions
EXPANDED PIN DESCRIPTION
Pin 1:
(VREF)
Internal .9V reference
Connected to the + input of the master channel error
amplifier.
Pin 2:
(+IN2)
+ Input of slave channel error amplifier.
Connected to .9V reference (Pin 1) for
2 independent channel configuration.
Pin 3, 18:
(-IN2, -IN1)
- Inputs of close loop error amplifiers.
Works as a feedback inputs (For both modes).
Pin 4:
(VCC)
VCC chip supply voltage.
15V maximum, 15mA typical.
Needs a 1µF ceramic multilayer decoupling capacitor
to GND (Pin 20).
Pin 5, 6,15, 16:
(CL2-, CL2+, CL1+, CL1-)
Pins (-) and (+) of the current limit amplifiers for both
channels.
Connected to output current sense resistors. Com-
pares that sense voltage to internal 75mV reference.
Needs RC filter for noise rejection.
Pin 7, 14:
(BST2, BST1)
BST signal. Supply for high side driver.
Can be connected to a high enough voltage source.
Usually connected to bootstrap circuit.
2006 Semtech Corp.
5
Pin 8, 13:
(DH2, DH1)
DH signal (Drive High).
Gate drive for top MOSFETs.
Requires a small serie resistor.
Pin 9, 12:
(DL2, DL1)
DL signal (Drive Low).
Gate drive for bottom MOSFETs.
Requires a small serie resistor.
Pin 10:
(PGND)
Power GND. Return of gate drive currents.
Pin 11:
(BSTC)
Supply for bottom MOSFETs gate drive.
Pin 17:
(SS/ENA)
Soft start pin. Internal current source connected to
external capacitor.
Inhibits he chip if pulled down.
Pin 19:
(PWRGD)
Power good signal.
Open collector signal .
Turns to 0 if output voltage is outside the power good
window.
Pin 20:
(GND)
Analog GND.
Return of analog signals and bias of chip.
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