CHERRY CS3972YDW16

CS3972
CS3972
1.25A High Efficiency Switching Regulator
Features
Description
The CS3972 is a 1.25A, 60V, current
mode, high efficiency, switching
regulator circuit. It can be configured in buck, boost, forward, isolated and non-isolated topologies,
using a single-ended switch.
The IC contains a 1.25A high efficiency output switch, precision
bandgap reference, voltage regulator, error amplifier, oscillator, control, and protection circuitry.
Output transistor efficiency is
achieved by keeping the switch in
quasi-saturation when it is on. This
minimizes the switch turn-off
delay time and power dissipation,
an important consideration for
applications with wide ranging
loads.
The precision reference is internally
trimmed to 1.24V, while the oscillator frequency is internally trimmed
to 40kHz. The on board 2.3V regulator powers the internal circuitry.
By keeping the voltage regulator at
2.3V, the IC is able to operate down
to 3V and maintain a constant input
supply current of 6mA(typ).
Synchronization mode is achieved
by applying a pulsating VC voltage
of less than 0.2V with a duration of
about 0.5µs to VC pin. The switching frequency can be adjusted from
50kHz to 70kHz. The IC's synchronization mode is set externally.
Protection circuitry includes a variable current limit with external
voltage clamp, under-voltage and
over-temperature protection.
■ 75VMAX, 2APEAK Internal
Switch
■ 3V to 60V Input Voltage
Range
■ 6mA Input Supply
Current
■ 1.24V Precision Reference
■ 40kHz Switching
Frequency
■ Variable Current Limit
with External Voltage
Clamp
■ Under-Voltage Protection
■ Over-Temperature
Protection
■ External Synchronization
Package Options
Block Diagram
16L SO Wide
NC
VSW
Output
Protection
2.3V
Reg
VIN
40kHz
OSC
Logic
+
1.25A,
75V
Switch
Driver
Gnd
1
VC
NC
VFB
E2
NC
VSW
NC
NC
NC
E1
NC
NC
NC
VIN
8L PDIP
COMP
5L TO-220
Tab (Gnd)
-
VC
Gnd 1
Error
Amp
VFB
+
E2
VC
+
Current
Amp
-
0.22Ω
0.22Ω
1.24V
Ref
VSW
VFB
E1
NC
VIN
1 VC
E2 *
2 VFB
E1 *
3 Gnd
Gnd
4 VSW
5 VIN
*Always connect E1 to Ground Pin on DIP package. Both emitters are tied to ground on TO-220 Package.
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Cherry Semiconductor Corporation
2000 South County Trail, East Greenwich, RI 02818
Tel: (401)885-3600 Fax: (401)885-5786
Email: info@cherry-semi.com
Web Site: www.cherry-semi.com
Rev. 6/23/99
1
A
®
Company
CS3972
Absolute Maximum Ratings
Input Voltage Range ........................................................................................................................................................3V to 60V
Output Switching Voltage.........................................................................................................................................................75V
Voltage Transient (tr=10µs, tf=400ms) ......................................................................................................................................60V
ESD (Human Body Model; R=1.5kΩ, C=100pF) ...................................................................................................................2kV
Junction Temperature Range...............................................................................................................................-40°C to +150°C
Storage Temperature Range ................................................................................................................................-65°C to +150°C
Lead Temperature Soldering
Wave Solder (through hole styles only)......................................................................................10 sec. max, 260°C peak
Reflow (SMD styles only) ......................................................................................60 sec. max above 183°C, 230°C peak
Feedback Pin Voltage (1ms transient)...................................................................................................................................±15V
Electrical Characteristics: For 3V≤VCC≤60V, -40°C≤TA≤125°C unless otherwise specified.
PARAMETER
TEST CONDITIONS
MIN
TYP
1.214
1.244
MAX
UNIT
■
Reference Voltage
Line Regulation
Feedback Input Current
Minimum Input Voltage
Supply Current
Supply Current Increase
during switch on time
Switching Frequency
Maximum Duty Cycle
VC Threshold
■ Error Amplifier
Transconductance
Source/Sink Current
High Voltage Clamp
Low Voltage Clamp
Gain
■ Output Switch
Breakdown Voltage
On Resistance
Control Voltage to Switch
Current Transconductance
Current Limit
VC=0.8V; VFB=VREF
VC=0.8V; VFB=VREF, 3V≤VIN≤60V
VC=0.8V; VFB=VREF
1.274
V
0.03
%/V
350
1100
nA
VC=VFB=VREF
VC=0.6V; 3V≤VIN≤60V
2.6
6.0
3.0
9.0
V
mA
VC=open, 1.0V≤VFB≤1.5V
VC=VFB=VREF; VSW=15V
VC=2V; VFB=open, VSW=15V
VFB=open; VSW =15V,
duty cycle=0%
25
40
92
0.90
33
0.60
VC=0.8V; VFB=VREF, ∆IC=±25µA
VC=1.5V
VFB=1.0V
VFB=1.5V
0.9V≤VC≤1.4V, VFB=VREF
2400
120
4400
200
2.0
0.38
800
VC=0.5V; 3V≤VIN≤60V, IOUT=5mA
VC=open, VFB=0.8V, IOUT=1.25A
1.2V≤VC≤1.8V
75
90
0.6
2
Duty Cycle≤50%, TJ≥25°C
Duty Cycle≤50%, TJ<25°C
Duty Cycle=80%
Duty Cycle=80% (Note 1)
1.25
1.25
1.00
0.50
Note 1: 16 lead SO wide package only.
2
47
1.25
7000
400
mA/A
kHz
%
V
µmho
µA
V
V
V/V
1.0
V
Ω
A/V
3.00
3.50
2.50
2.50
A
A
A
A
CS3972
Package Pin Description
PACKAGE PIN #
PIN SYMBOL
FUNCTION
16L
SO Wide
5L
TO-220
8L
PDIP
16
3
1
Gnd
Logic and power ground on TO-220. Logic ground only on 8L
PDIP.
2
1
2
VC
Control voltage can be used for frequency compensation, current limit threshold, frequency synchronization, and soft start.
3
2
3
VFB
Feedback voltage is the negative input to the error amplifier.
4
NC
No connection.
5
VIN
Supply input voltage with a range of 3V to 60V.
6
E1
Emitter One is a power ground which should always be connected to logic ground since it is used as the negative input to
the current sense amp.
7
VSW
8
E2
1,4,5,6,7,8,
10,12,15
9
5
11
13
4
14
Collector of internal 75V NPN power switch.
Emitter Two is a power ground which can be left disconnected
to reduce the switch rating to 625mA.
Typical Performance Characteristics
Switching Frequency vs. Temperature
1.274
47
1.264
45
Driver Current vs. Switch Current
100
90
80
1.254
1.244
1.234
1.224
43
Driver Current (mA)
Frequency (kHz)
Reference Voltage (V)
Reference Voltage vs. Temperature
41
39
37
35
70
60
50
40
30
20
10
1.214
-50
-25
-0
25
50
75
100
125
33
-50
150
-25
-0
Temperature (°C)
25
50
75
100
125
150
Temperature (°C)
1.6
97
Switch Saturation Voltage (V)
Tj=25°C
Duty Cycle (%)
96
95
93
92
91
90
-50
-25
-0
25
50
75
100
Junction Temperature (°C)
125
150
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
0
0.25
0.50
0.75
1.00
1.25
1.50
Switch Current (A)
3
0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
Switch Current (A)
Switch Saturation Voltage
Maximum Duty Cycle
0
1.75
2.0
1.6
1.8
2.0
CS3972
Circuit Description
The CS3972 has an on board, high current NPN transistor
in its output stage. The output transistor is switched on
every 25µs by the on board 40 kHz oscillator. The output
is switched off as soon as the output current reaches a
dynamically controlled level. That level is determined by
three factors: the current drawn by the load, the input
voltage, and the output voltage. This control scheme has
several benefits. The IC reacts quickly to overvoltage and
short circuit conditions and it is less sensitive to input
voltage fluctuation.
Current drawn by the load influences when the output
stage turns off. The voltage across the internal high precision resistor (0.11Ω) in the emitter of the output transistor
generating the input to the current sensing amplifier. The
output of the current sensing amplifier provides one of the
inputs to the comparator.
The other input to the comparator connected to the output of the error amplifier whose inverting input is connected to the output voltage through the feedback circuitry while its noninverting input is set to an internal reference voltage of 1.24V. When the current sensing amplifier
output exceeds the error amplifier output, the comparator
switches off, triggering the logic which turns off the output stage.
All on board amplifier, logic and protection circuitry uses
the internal 2.3V reference to minimize quiescent current
drain (6mA) and permits IC operation down to 3V.
The anti-saturation circuitry minimizes output switch
turn off time and power dissipation, by keeping the
power NPN at the edge of saturation.
Application Diagrams
L1
VIN
D1
VOUT
VIN
L1
Q1
R2
VOUT
R1
R3
VSW
VSW
VIN
VIN
VFB
CS3972
VC
(1.24V)
Gnd
C3
VC
(1.24V)
VFB
CS3972
+
+
C3
Gnd
+
+
C1
C1
R3
R1
R4
R2
D1
C2
C2
Figure 1: Boost Regulator
Figure 2: Buck Regulator with the External Switch
VOUT1
+
TR1
VIN
L1
D1
+VIN
VOUT
TR1
C5
+
C4
C3
D2
VOUT2
R1
C1
+
D3
C6
C5
1/2
OC1
R4
VSW
VIN
CS3972
VC
+
C2
VFB
(1.24V)
C2
+
R5
VSW
VIN
VC
R6
VFB
CS3972
R1
C4
Gnd
Gnd
–VIN
C3
Figure 3: Flyback Multiple Output Regulator
U1
1/2
OC1
R2
R5
R2
C3
D1
R7
R3
Figure 4: Isolated Forward Regulator
4
R4
CS3972
Package Specification
PACKAGE THERMAL DATA
PACKAGE DIMENSIONS IN mm (INCHES)
D
Lead Count
Metric
Max Min
10.16 9.02
10.50 10.10
8 Lead PDIP
16 Lead SO Wide
Thermal Data
English
Max Min
.400 .355
.413 .398
RΘJC
RΘJA
typ
typ
5L
TO-220
1.7
50
8L
PDIP
52
100
Plastic DIP (N); 300 mil wide
7.11 (.280)
6.10 (.240)
8.26 (.325)
7.62 (.300)
1.77 (.070)
1.14 (.045)
2.54 (.100) BSC
3.68 (.145)
2.92 (.115)
.356 (.014)
.203 (.008)
0.39 (.015)
MIN.
.558 (.022)
.356 (.014)
REF: JEDEC MS-001
Some 8 and 16 lead
packages may have
1/2 lead at the end
of the package.
All specs are the same.
D
Surface Mount Wide Body (DW); 300 mil wide
7.60 (.299)
7.40 (.291)
10.65 (.419)
10.00 (.394)
0.51 (.020)
0.33 (.013)
1.27 (.050) BSC
2.49 (.098)
2.24 (.088)
1.27 (.050)
0.40 (.016)
2.65 (.104)
2.35 (.093)
0.32 (.013)
0.23 (.009)
D
REF: JEDEC MS-013
5
0.30 (.012)
0.10 (.004)
16L
SO Wide
23
105
˚C/W
˚C/W
CS3972
Package Specification
5 Lead TO-220 (T) Straight
5 Lead TO-220 (TVA) Vertical
4.83 (.190)
4.06 (.160)
10.54 (.415)
9.78 (.385)
2.87 (.113)
6.55 (.258) 2.62 (.103)
5.94 (.234)
4.83 (.190)
4.06 (.160)
10.54 (.415)
9.78 (.385)
1.40 (.055)
1.14 (.045)
3.96 (.156)
3.71 (.146)
1.40 (.055)
1.14 (.045)
6.55 (.258)
5.94 (.234)
3.96 (.156)
3.71 (.146)
2.87 (.113)
2.62 (.103)
14.99 (.590)
14.22 (.560)
14.99 (.590)
14.22 (.560)
1.78 (.070)
2.92 (.115)
2.29 (.090)
8.64 (.340)
7.87 (.310)
14.22 (.560)
13.72 (.540)
4.34 (.171)
1.68
(.066) typ
1.70 (.067)
1.02 (.040)
0.76 (.030)
7.51 (.296)
0.56 (.022)
0.36 (.014)
6.80 (.268)
.94 (.037)
.69 (.027)
1.83(.072)
1.57(.062)
1.02(.040)
0.63(.025)
0.56 (.022)
0.36 (.014)
6.93(.273)
6.68(.263)
2.92 (.115)
2.29 (.090)
5 Lead TO-220 (THA) Horizontal
4.83 (.190)
10.54 (.415)
9.78 (.385)
2.87 (.113)
2.62 (.103)
1.40 (.055)
4.06 (.160)
1.14 (.045)
3.96 (.156)
3.71 (.146)
14.99 (.590)
14.22 (.560)
6.55 (.258)
5.94 (.234)
2.77 (.109)
6.83 (.269)
1.68
(.066)
TYP
1.70 (.067)
0.81(.032)
2.92 (.115)
2.29 (.090)
0.56 (.022)
0.36 (.014)
6.60 (.260)
5.84 (.230)
6.81(.268)
Ordering Information
Part Number
CS3972YN8
CS3972YDW16
CS3972YDWR16
CS3972YT5
CS3972YTVA5
CS3972YTHA5
Rev. 6/23/99
Description
8L PDIP
16L SO Wide
16L SO Wide (tape & reel)
TO-220 Straight
TO-220 Vertical
TO-220 Horizontal
Cherry Semiconductor Corporation reserves the
right to make changes to the specifications without
notice. Please contact Cherry Semiconductor
Corporation for the latest available information.
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© 1999 Cherry Semiconductor Corporation