NOT RECOMMENDED FOR NEW DESIGN
SC412A
Synchronous Buck Controller
POWER MANAGEMENT
Description
The SC412A is a versatile, constant on-time synchronous
buck, pseudo
fi
xed-frequency, PWM controller intended
for notebook computers and other battery operated
portable devices. The SC412A contains all the features
needed to provide cost-effective control of switch-mode
power outputs.
The output voltage is programmable from 0.75 to 5.25
volts using external resistors. Switching frequency is
internally preset to 325kHz. Additional features cycle-
by-cycle current limit, voltage soft-start, under-voltage
protection, programmable over-current protection, soft
shutdown, automatic power save and non-overlapping
gate drive. The SC412A also provides an enable input
and a power good output.
Features
V
BAT
Range 3V to 25V
Soft-Shutoff at Output
Current Sense Using Low-Side R
DS(ON)
or Resistor
Sensing with Adjustable Cycle-by-Cycle Current Limit
Fixed-Frequency 325kHz
Constant On-Time for Fast Dynamic Response and
Reduced Output Capacitance
Automatic Smart Power Save
†
Internal Soft-Start
Over-Voltage/Under-Voltage Fault Protection
Power Good Output
1μA Typical Shutdown Current
Tiny 3x3mm, 16 Pin MLP, Lead-free Package
Low External Part Count
Industrial Temperature Range
1% Internal Reference
1A/3A Non-Overlapping Gate Drive with SmartDrive™
High Efficiency > 90%
Fully WEEE and RoHS Compliant
The constant on-time topology provides fast, dynamic
response. The excellent transient response means that
SC412A based solutions require less output capacitance
than competing
fi
xed-frequency converters. Switching
frequency is constant until a step in load or line voltage
occurs, at which time the pulse density and frequency
will increase or decrease to counter the change in
output voltage. After the transient event, the controller
frequency returns to steady state operation. At light loads,
the automatic power save mode reduces the switching
frequency for improved efficiency.
Typical Application Circuit
VCC
VBAT
CIN
Q1
N
O
T
FO R
R EC
N O
EW M
M
D EN
ES D
IG ED
N
†
Patent pending
Applications
Notebook and Sub-Notebook Voltage Controllers
Tablet PCs
Embedded Applications
C1
D1
RLIM
VCC
16
15
14
DH
L1
VOUT
ILIM
NC
NC
C2
1
2
LX
BST
VCC
DL
PAD
13
R1
EN
12
11
10
9
EN
PGOOD
VOUT
FB
U1
PGOOD
VOUT
FB
COUT
Q2
VCC
3
4
SC412A
GND
RTN
NC
NC
R2
17
7
5
6
8
R3
October 25, 2007
1
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NOT RECOMMENDED FOR NEW DESIGN
SC412A
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. Exposure to Absolute Maximum rated conditions for extended periods of time
may affect device reliability.
Parameter
D
H
, B
ST
to G
ND
(DC)
D
H
, B
ST
to G
ND
(transient - 100nsec max)
D
L
to G
ND
(DC)
D
L
to G
ND
(transient - 100nsec max)
L
X
to G
ND
(DC)
L
X
to G
ND
(transient - 100nsec max)
B
ST
to L
X
R
TN
to G
ND
V
CC
to R
TN
Symbol
Min
-0.3
-2.0
-0.3
-2.0
-0.3
-2.0
-0.3
-0.3
-0.3
-0.3
-40
-60
45
Max
+30
+33
+6.0
+6.0
+25
+28
+6.0
+0.3
+6.0
V
CC
+ 0.3
+125
+150
o
Units
V
V
V
V
V
V
V
o
o
E
N
, F
B
, I
LIM
, P
GOOD
, V
CC
, V
OUT
to R
TN
Storage Temperature Range
Operating Junction Temperature Range
N
O
T
FO R
R EC
N O
EW M
M
D EN
ES D
IG ED
N
T
J
C
C
T
STG
θ
JA
Thermal Resistance, Junction to Ambient
(1)
C/Watt
o
Peak IR Reflow Temperature, 10-40 Second
ESD Rating (Human Body Model)
T
PKG
+260
C
2
kV
Note:
(1) Calculated from package in still air, mounted 3” to 4.5”, 4 layer FR4 PCB with thermal vias under the exposed pad per JESD51 standards.
Electrical Characteristics
Test Conditions: V
BAT
= 15V, V
OUT
= 1.5V, T
A
= 25
o
C, 0.1% resistor dividers; V
CC
= 5.0V, unless otherwise noted.
25°C
Typ
-40° to 85°C
Units
Min
Max
Parameter
Input Supplies
VBAT Input Voltage
Conditions
Min
Max
3.0
EN = 0V
FB > REF
1
500
25
5
1000
V
μA
μA
VCC Shutdown Current
VCC Operating Current
Controller
FB On-Time Threshold
Regulation
Line Regulation Error
Load Regulation Error
0.75
Typical Application Circuit
Typical Application Circuit
0.04
0.3
0.7425
0.7575
V
%/V
%
© 2006 Semtech Corp.
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NOT RECOMMENDED FOR NEW DESIGN
SC412A
POWER MANAGEMENT
Electrical Characteristics
(continued)
25°C
Parameter
Logic Inputs/Outputs
(continued)
EN Input Bias Current
FB Input Bias Current
Power Good Output
Low Voltage
Gate Drivers
Shoot-Through
Protection Delay
(1)
EN = V
CC
or R
TN
FB = V
CC
or R
TN
R
PWRGD
= 10kΩ to V
CC
-1
-1
+1
+1
0.4
μA
μA
V
Conditions
Min
Typ
Max
Min
Max
-40° to 85°C
Units
N
O
T
FO R
R EC
N O
EW M
M
D EN
ES D
IG ED
N
DH or DL Rising
DL Low
30
ns
1.6
Ω
A
4
Ω
A
4
4
Ω
Ω
A
DL Pull-Down Resistance
DL Sink Current
0.8
V
DL
= 2.5V
DL High
3.1
2
DL Pull-Up Resistance
DL Source Current
V
DL
= 2.5V
1.3
2
DH Pull-Down Resistance
DH Pull-Up Resistance
(2)
DH Sink/Source Current
DH Low, B
ST
- L
X
= 5V
DH High, B
ST
- L
X
= 5V
V
DH
= 2.5V
2
1.3
Notes:
(1) Guaranteed by design.
(2) Semtech’s SmartDriver™ FET drive
fi
rst pulls DH high with a pull-up resistance of 10Ω (typical) until LX = 1.5V (typical). At this point,
an additional pull-up device is activated, reducing the resistance to 2Ω (typical). This negates the need for an external gate or boost
resistor.
© 2006 Semtech Corp.
4
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NOT RECOMMENDED FOR NEW DESIGN
SC412A
POWER MANAGEMENT
Pin Configuration
ILIM
DH
NC
NC
Ordering Information
Device
SC412AMLTRT
(1)
SC412AEVB
12
11
10
Package
(2)
MLPQ-16 3X3
Evaluation Board
16
15
14
13
LX
BST
VCC
DL
1
2
3
4
5
TOP VIEW
EN
PGOOD
VOUT
FB
T
6
7
8
9
Notes:
1) Available in tape and reel packaging only. A reel contains 3000
devices.
2) Available in lead-free packaging only. This product is fully WEEE,
RoHS and J-TD-020B compliant. This component and all homog-
enous sub-components are RoHS compliant.
MLPQ16: 3X3 16 LEAD
Marking Information
Marking for the 3 x 3mm MLPQ 16 Lead Package
nnnn = Part Number (example: 412A)
yyww = Date Code (example: 0652)
xxxx = Semtech Lot No. (example: E901)
© 2006 Semtech Corp.
N
O
T
FO R
R EC
N O
EW M
M
D EN
ES D
IG ED
N
NC
RTN
GND
412A
yyww
xxxx
NC
5
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