SC2603SKTRT [SEMTECH]
Simple PWM Boost Controller; 简单的PWM升压控制器
| 型号： | SC2603SKTRT |
| 厂家： | 
SEMTECH CORPORATION |
| 描述： | Simple PWM Boost Controller |
| 文件： | 总11页 (文件大小：225K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
SC2603
Simple PWM Boost Controller
POWER MANAGEMENT
Description
Features
The SC2603 is a versatile, low-cost, voltage-mode PWM
controller designed for 16V input DC/DC power supply
applications. A simple, fixed-voltage boost regulator can
be implemented using the SC2603 with a minimum of
external components. The small device footprint
allows for compact circuit design.
u Low cost / small size
u Switch mode efficiency up to 95%
u 1% reference voltage accuracy
u Over-current protection
u 800mA output drive
u 5V to 16V input power source
u No need for external compensation network
u SOT23-6 is fully WEEE and RoHS compliant
SC2603 features include a temperature compensated
voltage reference, triangle wave oscillator, current limit
comparator, frequency shift over-current protection, and
an internally compensated error amplifier. Pulse by pulse
current limiting is implemented by sensing the
differential voltage across an external resistor, or an
appropriately sized PC board trace.
Applications
u Portable Devices
u Flat Panel TV
u TV Set Top Box
u Auxiliary Supplies
The SC2603 operates at a fixed frequency of 200kHz,
providing an optimum compromise between efficiency,
external component size, and cost.
u Peripheral Card Supplies
u Industrial Power Supplies
u High Density DC/DC Conversion
Typical Application Circuit
D1
L1
VIN
VOUT
R1
R2
C1
C2
Q1
D2
C3
U2
GND
optional
R3
5
3
1
4
6
2
VIN
Gate
Enable
EN/SS CS
FB
GND
R4
Open Drain with < 100Ω
pull down impedance
C4
C5
R5
SC2603
1
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Revision: Nov 14, 2006
SC2603
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.
Parameter
Symbol
VIN to GND
TSTG
Maximum
-0.3 to 20
-45 to +150
150
Units
V
Input Voltage
Storage Temperature Range
Maximum Junction Temperature
Lead Temperature (Soldering) 10 Sec.
Thermal Resistance, Junction to Ambient(1)
Thermal Resistance, Junction to Case
°C
TJ
°C
TLEAD
θJA
300
°C
165
°C/W
°C/W
KV
102
θJC
Electrical Surge Discharge(2)
ESD
2
Note:
(1) Mounting pad has to be larger than one square inch on two sided printed circuit board with minimum 1 ounce copper
(2) Human model.
Electrical Characteristics
VIN= 12V; VO = 25V; TA = TJ = -40°C to 125°C unless otherwise specified.
Parameter
Symbols
Conditions
Min
Typ
1.250
2.0
5.0
0.5
1.4
73
Max
1.275
8.0
Units
V
Reference
VREF
IFB
1.225
Feedback Bias Current
Quiescent Current
Load Regulation
VFB = VEN/SS, VIN = 12V
Current into VIN pin
µA
mA
%
IQ
8.0
VO=25V ; IO = 0.1A to 1A
VIN=5V to 15V ; VO=25V ; IO = 100mA
CS
1.0
Line Regulation
2
%
Current Limit Threshold
Oscillator Frequency
Oscillator Frequency Shift
Max Duty Cycle
68
78
mV
kHz
kHz
%
O
TA = 25 C
190
200
50
210
VFB < VREF/2
90
95
UVLO Threshold
VUVLO
VIN ramping up
4.2
400
0.8
0.8
60
4.5
V
UVLO Hysteresis
Driver Source Current
Driver Sink Current
Soft Start Charge Current
Internal Ramp Peak
Internal Ramp Valley
mV
A
ISOURCE
ISINK
VIN = 12V, CGATE = 10nF
VIN = 12V, CGATE = 10nF
0.5
0.5
1.1
1.1
A
ISS
µA
V
VR_PEAK
VR_VALLEY
1.4
0.4
V
Pull down below this level
to disable the output
Enable Threshold
VTH_EN
0.09
0.12
V
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2
SC2603
POWER MANAGEMENT
Pin Configuration
Ordering Information
Part Numbers
SC2603SKTRT(1)(2)
SC2603EVB
Package
SOT23-6
Top View
FB
CS
1
2
6
5
4
GND
VIN
GATE
EN/SS
3
Note:
(1) Only available in tape and reel packaging. A reel
contains 3000 devices.
(2) Lead free product. This product is fully WEEE and
RoHS compliant
SOT23-6
Pin Descriptions
Pin #
Pin Name
Pin Function
1
2
3
4
5
6
FB
GND
EN/SS
Gate
VIN
Error amplifier input (-).
Device ground.
Enable/Soft Start Pin.
Gate driver output.
Device Input Voltage.
Current Sense Input .
CS
Block Diagram
OSCILLATOR
VIN
S
PWM
Q
FB
Gate
R
GND
25K
Current
Limit
CS
EN/SS
1.25V
REF
70mV
UV
VIN
UVLO
1.25V
REF
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3
SC2603
POWER MANAGEMENT
Theory of Operation
Application Information
The SC2603 is a versatile, low-cost, voltage-mode PWM
controller designed for DC/DC power supply applications.
In normal condition, the SC2603 operats at a fixed
200KHz. One exception is that when the FB pin voltage
drops to one half, the frequency will be shifted to one
fouth of 200KHz.
Soft-Start
Soft-start prevents a DC-DC converter from drawing
excessive current from the power source during start up.
If the soft-start time is made sufficiently long, then the
output will enter regulation without overshoot. An external
capacitor is connected from the EN/SS pin to the ground.
After the part’s input voltage surpasses the UVLO, the
EN/SS pin is allowed to charge its capacitor with 60µA.
When 100mV is reached at the EN/SS pin, the internal
comp node is at 0.4V. The SC2603 will start switching,
and the converter output comes into regulation. Because
the FB pin voltage follows EN/SS pin voltage, finally, the
EN/SS pin voltage will be clamped at 1.25V same as the
refernece voltage.
SC2603 features include a temperature compensated
voltage reference, triangle wave oscillator, current limit
comparator, frequency shift over-current protection, and
an internally compensated error amplifier. Pulse by pulse
current limiting is implemented by sensing the
differential voltage across an external resistor, or an
appropriately sized PC board trace.
Setting the Output Voltage
An external resistive divider R1 and R2 with its center
tap tied to the FB pin sets the output voltage.
VOUT
V
SC2603
OUT
R1
R2
R1 = R
− 1
2
1.25
1
FB
Under Voltage Lockout
The under voltage lockout circuit of the SC2603 assures
that the gate driver output remains in the off state when-
ever the supply voltage drops below set parameters. Lock-
out occurs if VIN falls below 3.8V. Normal operation re-
sumes once VIN rises above 4.2V.
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SC2603
POWER MANAGEMENT
Application Information
Over Current Protection
The over-current protection is implemented by a sensing
resistor and an internal current-limit comparator with a
threshold of 70mV. If the switching current through the
sensing resistor causing voltage to drop at the CS pin
reachs 70mV, the SC2603 will immediately turn the gate
pulse off to limit the current through the power switch.
The figure below shows over-current waveforms. At t1,
the input current IIN begins to increase as the load IOUT
builds up until it hits the OCP threshold at t2. At t2, VOUT
begins to drop as IOUT starts increasing toward t3 while VIN
and IIN remain the same. At t3, there two events are
happening. 1) VOUT is at half of its regulating voltage. At
this point, the internal oscillator runs into frequency shift
mode and shifts the frequency to one fourth of the oper-
ating frequency. 2) The diode starts conducting current
without limit causing VIN to fall due to supply current limit.
Finally, VIN and VOUT both drops to zero and IIN becomes the
input supply current limit.
A RC filter at the CS pin is necessary to filter out noise to
ensure accurate sensing.
The value of the sensing resistor can be caculated by
the following equation:
RS = 70 mV / I PEAK
Where IPEAK is the input peak current through the power
MOSFET.
IIN
IOUT
VOUT
VIN
t0
t2
t3
t1
t4
Over Current Waveforms
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SC2603
POWER MANAGEMENT
Applications Information
Layout Guidelines
5) The SC2603 is best placed over an isolated ground
plane area. The soft-start capacitor, the VIN decoupling
capacitor, and the current sensing filter capacitor should
also connected to this ground pad area. This isolated
ground area should be connected to the main ground by
a trace that runs from the GND pin to the ground side of
the output capacitor. If this is not possible, the GND pin
may be connected to the ground path between the Out-
put Capacitor and the Cin, Q1, D1 loop. Under no cir-
cumstances should GND be returned to a ground inside
the Cin, Q1, D1 loop.
Careful attention to layout requirements are necessary
for successful implementation of the SC2603 PWM con-
troller. High currents switching at 200kHz are present in
the application and their effect on ground plane voltage
differentials must be understood and minimized.
1) The high power parts of the circuit should be laid out
first. A ground plane should be used, the number and
position of ground plane interruptions should be such as
to not unnecessarily compromise ground plane integrity.
Isolated or semi-isolated areas of the ground plane may
be deliberately introduced to constrain ground currents
to particular areas, for example the input capacitor and
bottom Schottky ground.
6) Input voltage of the SC2603 should be supplied from
the power rail through a 2.2~10Ω resistor, the VIN pin
should be decoupled directly to GND by a 0.1µF~1µf
ceramic capacitor, trace lengths should be as short as
possible.
2) The loop formed by the output Capacitor(s) (Cout), the
FET (Q1), the current sensing resistor, and the Schottky
(D1) must be kept as small as possible. This loop con-
tains all the high current, fast transition switching. Con-
nections should be as wide and as short as possible to
minimize loop inductance. Minimizing this loop area will
reduce EMI, lower ground injection currents, resulting in
electrically “cleaner” grounds for the rest of the system
and minimize source ringing, resulting in more reliable
gate switching signals.
7) An RC low pass filter is required to filter out leading
edge current spikes on the current sensing resistor. The
filter capacitor needs to be very close to the CS and
GND to reduce noise pickup.
3) The connection between the junction of Q1, D1 and
the output capacitor should be a wide trace or copper
region. It should be as short as practical. Since this con-
nection has fast voltage transitions, keeping this con-
nection short will minimize EMI.
4) The Output Capacitor(s) (Cout) should be located as
close to the load as possible, fast transient load cur-
rents are supplied by Cout only, and connections be-
tween Cout and the load must be short, wide copper
areas to minimize inductance and resistance.
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SC2603
POWER MANAGEMENT
Applications Information (Cont.)
Layout diagram for the SC2603
Vout
12VIN
Ra
20uH
D1
Q1
Cin
+
2.2
SC2603
VIN
Cout
Rb
1
5
3
FB
Gate
GND
4
EN/SS
CS
0.1uF
0.1uF
Rs
2
6
Heavy lines indicate the critical loop carrying high pulsating current.
The inductance of this loop needs to be minimized.
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SC2603
POWER MANAGEMENT
Applications Circuit
12V to 25V @ 1A boost converter
D1
L1
VOUT=25V
VIN = 12V
18uH
R1
2.2
C1
3A, 40V
R2
470u
34K
C2
C11
1u
Q1
AO4442
C3
1u
330u/35V
U2
R4
5
3
1
4
6
2
VIN
Gate
1.78K
R5
1K
Enable
EN/SS CS
FB GND
Open Drain with < 100Ω
R6
C4
pull down impedance
0.1u
C5
20m
120p
SC2603
Bill of Material
Item
1
Quantity
Reference
C1
Part
footprint
Vendor
SANYO
SANYO
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
470u/Alum
330u/Alum
1uF
2
C2
3
C3
603
603
603
805
4
C4
0.1u
5
C5
120p
6
C11
D1
1u
7
1N5819
18uH
AO4442
2.2
8
L1
COOPER
9
Q1
Alpha & Omega
10
11
12
13
14
15
16
R1
603
603
603
603
603
R2
34K
R3
0
R4
1.78K
1K
R5
R6
20m
U1
SC2603
SOT23-6
SEMTECH
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2005 Semtech Corp.
8
SC2603
POWER MANAGEMENT
Typical Characteristics
Load Regulation (VIN = 12V, VO = 25V)
Error Amplifier: Gain and Phase
40
35
30
25
20
180
135
90
26
25.5
25
15
24.5
24
Gain
10
45
Phase
5
0
23.5
0
23
-5
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
-10
-45
Output Current - (A)
100.0E+0
1.0E+3
10.0E+3
100.0E+3
1.0E+6
10.0E+6
Frequency (Hz)
Efficiency (VIN = 12V, VO = 25V)
Line Regulation (VO = 25V, IO = 1A)
26.000
25.500
25.000
98
96
94
92
90
88
86
84
82
80
24.500
24.000
23.500
23.000
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
4
6
8
10
12
14
16
Input Voltage - (V)
Output Current - (A)
Frequency Shift (VFB vs. FSW)
OCP (VIN = 12V, VO = 25V)
25.6
25.4
25.2
25
24.8
24.6
24.4
24.2
0
0.5
1
1.5
2
2.5
3
Output Current - (A)
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9
SC2603
POWER MANAGEMENT
Typical Characteristics
UVLO Hysteresis vs Temperature
Reference Voltage vs Temperature
0.55
0.5
1.26
1.255
VIN=12V
1.25
1.245
1.24
0.45
0.4
0.35
0.3
VIN=5V
1.235
1.23
0.25
0.2
1.225
1.22
0.15
-50
-25
0
25
50
75
100
125
150
-50
0
50
TEMPERATURE ( C)
100
150
TEMPERATURE (oC)
O
Oscillator Frequency vs Temperature
Current Limit Threshold vs Temperature
210
205
200
195
190
185
180
75
74
73
72
71
70
69
68
-50
-25
0
25
50
75
100
125
150
O
-50
-25
0
25
50
75
100
125
150
TEMPERATURE ( C)
O
TEM PER ATURE ( C)
UVLO Threshold vs Temperature
4.30
4.28
4.25
4.23
4.20
4.18
4.15
4.13
4.10
4.08
4.05
-50
-25
0
25
50
75
100
125
150
O
T EM PE RA T UR E
(
C)
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2005 Semtech Corp.
10
SC2603
POWER MANAGEMENT
Outline Drawing - SOT23-6
DIMENSIONS
INCHES MILLIMETERS
DIM
A
MIN NOM MAX MIN NOM MAX
-
-
-
-
A
A1
A2
b
.057 0.90
.006 0.00
1.45
0.15
.035
.000
e1
D
E
.035 .045 .051 .90 1.15 1.30
-
-
-
-
.010
.003
.110
.020 0.25
.009 0.08
0.50
0.22
N
2X E/2
c
EI
D
E1
E
e
e1
L
L1
N
01
aaa
bbb
ccc
2.80
.114 .118
2.90 3.00
.060 .063 .069 1.50 1.60 1.75
1
2
2.80 BSC
0.95 BSC
1.90 BSC
.110 BSC
.037 BSC
.075 BSC
ccc C
2X N/2 TIPS
.012 .018 .024 0.30 0.45 0.60
e
(.024)
(0.60)
B
6
-
6
-
0°
10°
0°
10°
.004
.008
.008
0.10
0.20
0.20
D
aaa C
A2
A
SEATING
PLANE
C
H
H
A1
c
bxN
bbb
GAGE
PLANE
C A-B D
0.25
L
01
(L1)
A
DETAIL
SEE DETAIL A
SIDE VIEW
NOTES:
1. CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES).
2. DATUMS -A- AND -B- TO BE DETERMINED AT DATUM PLANE -H-
3. DIMENSIONS "E1" AND "D" DO NOT INCLUDE MOLD FLASH, PROTRUSIONS
OR GATE BURRS.
Land Pattern - SOT23-6
X
DDIIMMEENNSSIIOONNSS
DDIIMM
IINNCCHHEESS
(.098)
.055
.037
.024
MMIILLLLIIMMEETTEERRSS
(2.50)
1.40
0.95
0.60
1.10
3.60
CC
GG
PP
XX
(C)
G
Z
Y
Y
.043
.141
Y
ZZ
P
NOTES:
1. THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY.
CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR
COMPANY'S MANUFACTURING GUIDELINES ARE MET.
Contact Information
Semtech Corporation
Power Management Products Division
200 Flynn Road, Camarillo, CA 93012
Phone: (805)498-2111 FAX (805)498-3804
www.semtech.com
2005 Semtech Corp.
11
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