Low Power Dual Synchronous DC/DC
Controller With Current Sharing Circuitry
POWER MANAGEMENT
Description
The SC1175 is a versatile 2 phase, synchronous, volt-
age mode PWM controller that may be used in two dis-
tinct ways. First, the SC1175 is ideal for applications
where point of use output power exceeds any single in-
put power budget. Alternatively, the SC1175 can be used
as a dual switcher. The SC1175 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 SC1175 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.
SC1175
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 1.25V
Industrial temperature range
20 pin SOIC or TSSOP package
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: September 22, 2004
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SC1175
POWER MANAGEMENT
Typical Application Circuit
2 Channels with Current Sharing
2004 Semtech Corp.
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SC1175
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
Thermal Resistance Junction to Ambient
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
°C/W
°C
°C
°C
°C
θ
JC
θ
J A
T
A
T
J
T
STG
T
LEAD
30
90
0 to 85
0 to 125
-65 to +150
300
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
Load Regulation
Reference Line Regulation
Output Line 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
MIN
2.65
4.2
TYP
2.75
MAX
2.85
15
UNITS
V
V
mA
10
1.2375
1.25
1
.5
.5
35
60
270
90
70
300
95
80
330
1.2625
V
%
%
%
dB
mV
kHz
%
A
A
A
A
I
O
= 0.3A to 15A
(1)
5V < V
C C
< 15V
5V < V
IN
< 15V
V
OSENSE
to V
O
DH - PGND = 3.5V
DH - PGND = 1.75V
BSTH - DH = 5.0V
BSTH - DH = 2.5V
1
.5
1
.5
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SC1175
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
PARAMETER
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
CONDITIONS
DL - PGND = 3.5V
DL - PGND = 1.75V
BSTL - DL = 5V
BSTL - DL = 2.5V
Note 5
MIN
1
.5
1
.5
50
TYP
MAX
UNITS
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 = I
LIM
-IN1, +IN2, -IN2
1.25
50%
V
OUT
1
V
µA
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 70
°.
2004 Semtech Corp.
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SC1175
POWER MANAGEMENT
Pin Configuration
Top View
Ordering Information
Device
(1)
SC1175CSW.TR
SC1175CSWTRT
(2)
SC1175TS.TR
SC1175TSTRT
(2)
SC1175EVB-1
SC1175EVB-2
Current Share Version Evaluation
Board
Dual Channel Version Evaluation
Board
TSSOP-20
P ackag e
SOIC-20
(SOIC-20 and TSSOP-20 Pin)
Pin Descriptions
Expanded Pin Description
Pin 1: (VREF)
Internal 1.25V reference
Connected to the + input of the master channel error
amplifier.
Pin 2: (+IN)
+ Input of slave channel error amplifier.
Connected to 1.25V reference (Pin 1) for the two
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, 10mA typical.
Needs a 1µF ceramic multilayer decoupling capacitor
to GND (Pin 20).
6,1 16:
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.
Pin 8, 13: (DH2, DH1)
DH signal (Drive High).
Gate drive for top MOSFETs.
Requires a small series resistor.
2004 Semtech Corp.
Notes:
(1) Only available in tape and reel packaging. A reel
contains 1000 (SOIC) and 2500 (TSSOP) devices.
(2) Lead free product. This product is fully WEEE and
RoHS compliant.
Pin 9, 12: (DL2, DL1)
DL signal (Drive Low).
Gate drive for bottom MOSFETs.
Requires a small series resistor.
Pin 10: (PGND)
Power GND. Return of gate drive currents.
Pin 11: (BSTC)
Supply for bottom MOSFETs gate drive.
17
Pin 17: (SS/ENA)
Soft start pin. Internal current source connected to
external capacitor.
Inhibits the 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.
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