Simple, Synchronous
Voltage Mode PWM Controller
POWER MANAGEMENT
Description
The SC2608A is a versatile voltage-mode PWM control-
ler designed for use in step down DC/DC power supply
applications. A simple, fixed frequency, highly efficient
buck regulator can be implemented using the SC2608A
with minimal external components. The input voltage
range is from +5V to +12V. Internal level shift and drive
circuitry eliminates the need for an expensive P-channel,
high-side MOSFET. The small device footprint allows for
compact circuit design.
SC2608A features include temperature compensated
voltage reference, triangle wave oscillator, current limit
comparator, and an externally compensated error ampli-
fier. Current limit is implemented by sensing the voltage
drop across the bottom MOSFET R
DS(ON)
.
The SC2608A operates at a fixed frequency of 250kHz
providing an optimum compromise between efficiency ,
external component size, and cost.
SC2608A has a thermal protection circuit, which is
activated if the junction temperature exceeds 150
O
C.
SC2608A
Features
+5V or +12V input voltage
250kHz operation
High efficiency (>90%)
1.5% Reference voltage accuracy
Hiccup mode over current protection
Robust output drive
R
DS(ON)
Current sensing for protection
Industrial temperature range
SO-8 package
Integrated boot strap diode
Thermal Shut down
Fully WEEE and RoHS Compliant
Applications
Termination supplies
Low cost microprocessor supplies
Peripheral card supplies
Industrial power supplies
High density DC/DC conversion
Typical Application Circuit
SC2608
SC2608A
sense
COMP/SS SENSE
+12V/+5V/+3.3V
+12V
GND
VCC
DL
PHASE
DH
BST
VOUT
sense
Figure 1
Revision 2: April, 2006
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SC2608A
POWER MANAGEMENT
Absolute Maximum Ratings
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.
P ar am e t e r
V
CC
to GND
BST to PHASE
BST to GND
PHASE to GND
(note1)
DH to PHASE
(note1)
S y m b ol
M ax i m u m
+20
+15
+35
-1 to +24
+15
-1 to +15
+7
+7
Un i ts
V
V
V
V
V
V
V
V
O
O
DL to GND
(note2)
COMP/SS to GND
SENSE to GND
Thermal Resistance Junction to Case
Thermal Resistance Junction to Ambient
Op erating Temp erature Range
Storage Temp erature Range
ESD Rating (Human Body Model)
q
JC
q
JA
T
J
T
STG
ESD
40
120
-40 to +125
-65 to +150
2
C/W
C/W
O
O
C
C
kV
Note 1: Under pulsing condition, the peak negative voltage can not be lower than -3.6V with less than 20nS from 50% to 50%.
Note 2: Under pulsing condition, the peak negative voltage can not be lower than -5V with less than 20nS from 50% to 50%.
Electrical Characteristics
Unless specified: V
CC
= 12V, V
BST
- V
Phase
= 12 V, V
OUT
= 3.3V, T
J
= T
A
= 25
o
C.
P a r a m et er
P ow er Su p p l y
Supply Voltage
Supply Current
E r r or A m p l i f i er
Feedback Voltage
Sym b ol
C on d i t i on s
Mi n
Typ
Ma x
Un i ts
V
CC
I
CC
V
COMP
< 0.4V
4.5
6
14
V
mA
V
FB
4.75V<Vcc<12.6V
0
O
C < T
A
< 85
O
C
-4 0
O
C < T
A
< 1 2 5
O
C
0.788
0 .8
0.8
7
60
1
0.812
V
V
mS
dB
E/A Transconductance
Open Loop DC Gain
Input Bias Current
Output Sink Current
Output Source Current
G
m
A
O
I
FB
I
SINK
I
SOURCE
V
SENSE
> 0.9V; V
COMP
= 2.1V
V
SENSE
< 0.7V; V
COMP
= 2.1V
2
3
uA
uA
uA
-700
120
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2006 Semtech Corp.
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SC2608A
POWER MANAGEMENT
Electrical Characteristics
Unless specified: V
CC
= 12V, V
BST
- V
Phase
= 12 V, V
OUT
= 3.3V, T
J
= T
A
= 25
o
C.
P ar am e t e r
O s ci l l at o r
Switching Frequency
Ramp Peak Voltage
Ramp Valley Voltage
Maximum Duty Cycle
M O S F E T Dri v ers
DH Sink/Source Current
DL Sink/Source Current
DH Rise/Fall Time
DL Rise/Fall Time
Dead Time
DL Minimum On Time
Cu rren t L i m i t
Trip Voltage
S o f t - S t ar t
SS Source Current
SS Sink Current
U n d e r v o l t ag e L o ck o u t
UVLO Threshold
T h e r m al S h u t d o w n
Over Temp erature Trip Point
S y m b ol
Con d i t i on s
Mi n
Ty p
M ax
Un i ts
F
OSC
V
P -K
V
V
D
MAX
Vcc =12V
4.75V < V
CC
< 12.6V
4.75V < V
CC
< 12.6V
250kHz
225
250
1.8
0.8
85
275
kHz
V
V
%
I
DH
I
DL
tr, tf
tr, tf
t
d t
t
ON
t
PW
> 400nS
V
GS
= 4.5V (src)
V
GS
= 2.5V (snk)
C
L
= 3000p F, See Fig. 2
C
L
= 4000p F, See Fig. 2
See Fig. 2
4.75V < Vcc < 12.6V
0.6
0.6
0.8
0.7
50
50
80
400
A
A
ns
ns
ns
ns
V
T R IP
4.75V < Vcc < 12.6V
V
trip
= V
PHASE
- GND
-400
-350
-300
mV
I
SRC
I
SNK
V
COMP
< 2.5V
V
COMP
> 0.5V
6
-6
uA
uA
V
th
-40< T
J
< 85
O
C
3.9
4.1
4.3
V
T
OTP
150
o
C
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2006 Semtech Corp.
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SC2608A
POWER MANAGEMENT
Gate Drive Timing Diagram
Figure 2
Block Diagram
VCC
BST
DH
PHASE
OSC
S
+
REF
0.8V
R
-
Q
LEVEL
SHIFT
E/A
+
NON-OVERLAP
TIMING
0
PWM
VCC
OCP &
UVLO
SENSE
-
Vcc
DL
GND
0
OCP
PHASE
+
-
0
0
COMP/SS
Figure 3
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2006 Semtech Corp.
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SC2608A
POWER MANAGEMENT
Pin Configuration
Top View
Ordering information
Device
(1 )
Package
SO-8
Evaluation Board
Temp Range (T
J
)
-40 to 125
O
C
SC2608ASTRT
(2)
BST
DH
GND
DL
1
2
3
4
(8-Pin SO-8
)
8
7
6
5
PHASE
COMP/SS
SENSE
VCC
SC2608AEVB
Notes:
(1) Only available in tape and reel packaging. A reel con-
tains 2500 devices.
(2) This device is fully WEEE and RoHS Compliant
Pin Descriptions
Pin
#
1
2
3
4
5
6
P i n N am e
BST
DH
GN D
DL
VCC
Sense
COMP/SS
PHASE
Bootstrap for high side driver.
High side driver outp ut.
Ground.
Low side driver outp ut.
Chip bias sup p ly p in.
Outp ut voltage sense inp ut.
Error amp lifier outp ut. Connect comp ensation network to GN D. The comp ensation cap acitor
serves as soft star t cap acitor. By p ulling this p in low will disable the outp ut.
Connect this p in to the switching node between the MOSFETs.
P i n Fu n c t i o n
7
8
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2006 Semtech Corp.
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