Simple, Synchronous
Voltage Mode PWM Controller
POWER MANAGEMENT
Description
The SC1104A/B is a versatile voltage-mode PWM con-
troller designed for use in single ended DC/DC power
supply applications. A simple, fixed frequency high effi-
ciency buck regulator can be implemented using the
SC1104A/B with a minimum of external components.
Internal level shift and drive circuitry eliminates the need
for an expensive P-channel, high-side switch. The small
device footprint allows for compact circuit design.
SC1104A/B features include temperature compensated
voltage reference, triangle wave oscillator, current limit
comparator and an externally compensated error
amplifier. Current limit is implemented by sensing the
voltage drop across the top .ETs R
DS(ON).
.
The SC1104A/B operates at a fixed frequency of 300/
600 kHz, providing an optimum compromise between
efficiency, external component size, and cost. 600kHz
switching frequency is typically reserved for the 5V
operation only.
SC1104A/B has a thermal protection circuit, which is
activated if the junction temperature exceeds 150°C.
SC1104A/B
PRELIMINARY
.eatures
K
K
K
K
K
K
K
K
+5V or +12V operation
High efficiency (>90%)
1% Reference voltage accuracy
Hiccup mode over current protection
Robust output drive
R
DS(ON)
Current sensing
Industrial temperature range
SO-8 package
Applications
K
K
K
K
K
Termination supplies
Low cost microprocessor supplies
Peripheral card supplies
Industrial power supplies
High density DC/DC conversion
Typical Application Circuit
Typical Distributed Power Supply
R2
10
C3
0.1
D1
MBRA130L
U1
SC1104A/B
1
COMP/SS
SENSE
8
R3
1.00k
R5
200-1k
C8
0.1-0.22
2.32k
+
C4
10.0
C5
47/16V
C6
47/16V
C7
47/16V
C1
220-680pF
Vin 5 to 12V
_
R1
2k
C2
0.01
R4
2
GND
VCC
7
3
DL
PHASE
6
4
DH
BST
5
R8
10
R6
1-5.1
Q1
Si4884DY
C9
0.1
L1
1.5-3uH
Q2
Si4874DY
R7
1-5.1
D2
(opt)
C10
220/4V
C11
220/4V
C12
220/4V
C13
220/4V
C14-17
1.0
+
3.3V
_
.igure 1
Revision 3, October 2001
1
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SC1104A/B
POWER MANAGEMENT
Absolute Maximum Ratings
Parameter
V
CC
to GND
BST to PHASE
PHASE to GND
DH to PHASE
DL to GND
COMP/SS to GND
SENSE to GND
Thermal Resistance Junction to Case
Thermal Resistance Junction to Ambient
Operating Temperature Range
Storage Temperature Range
Lead Temperature (Soldering) 10 Sec.
θ
JC
θ
J A
T
A
T
STG
T
Lead
Symbol
Maximum
15
15
-1 to 15
15
15
7
7
40
160
-40 to +85
-65 to +150
300
PRELIMINARY
Units
V
V
V
V
V
V
V
°C/W
°C/W
°C
°C
°C
Electrical Characteristics
Unless specified:
A:
V
CC
= 12 ± 0.6V, V
BST
= 23 ± 1V, V
OUT
= 3.3V, T
A
= 25
o
C.
B:
V
CC
= 5 ± 0.25V, V
BST
= 12 ± 0.6V, V
OUT
= 2.0V, T
A
= 25
o
C
Parameter
Pow er Supply
Supply Voltage
Symbol
Conditions
Min
Typ
Max
Units
V
CC
V
CC
F
SW
= 300kHz (nom.), (SC1104A)
F
SW
= 600kHz (nom.), (SC1104B)
V
COMP
≤
0.4V
4.2
4.2
11
12.6
V
7
14
mA
Supply Current
Error Amplifier
E/A Transconductance
Input Bias Current
Output Sink Current
Source Current
Oscillator
Switching Frequency
I
CC
g
m
I
FB
I
SIK
I
SC
V
SENSE
≥
1.1V; V
COMP
= 1.5V
V
SENSE
≥
0.9V; V
COMP
= 1.5V
10
1
0.7
3
mS
µA
mA
1.1
F
OSC
V
CC
= 12V ± 0.6V
V
CC
= 5V ± 0.25V
270
540
300
600
2.0
330
660
kHz
V
Ramp Peak Voltage
V
P-K
4.75V
≤
VCC
≤
12.6V
©
2001 Semtech Corp.
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SC1104A/B
POWER MANAGEMENT
Pin Configuration
Top View
PRELIMINARY
Ordering Information
Device
(2)
P ackag e
SOIC-8
Temp Range (T
J
)
-40° to 125°C
SC1104XISTR
(1)
Note:
(1) In place of “X”: A = 300kHz; B = 600kHz.
(2) Only available in tape and reel packaging. A reel
contains 2500 devices.
(8-Pin SOI
C)
Pin Descriptions
Pin
#
1
2
3
4
5
6
7
8
Pin Name
COMP/SS
GND
DL
DH
BST
PHASE
VC C
SENSE
Pin Function
Error amplifier output. Compensation, soft start/enable.
Ground.
Low side driver output
High side driver output
Bootstrap, high side driver.
Input from the phase node between the MOSFETs.
Chip bias supply voltage.
Output voltage sense input.
©
2001 Semtech Corp.
5
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