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Cherry Semiconductor Corporation

CS52845 Datasheet Preview

CS52845 Datasheet

Current Mode PWM Control Circuit with 50% Max Duty Cycle

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CS52845
Current Mode PWM Control Circuit
with 50% Max Duty Cycle
Description
The CS52845 provides all the nec-
essary features to implement off-
line fixed frequency current-mode
control with a minimum number
of external components.
The CS52845 incorporates a new
precision temperature-controlled
oscillator to minimize variations in
frequency. An internal toggle flip-
flop, which blanks the output
every other clock cycle, limits the
duty-cycle range to less than 50%.
An undervoltage lockout ensures
that VREF is stabilized before the
output stage is enabled. In the
CS52845 turn on is at 8.4V and
turn off at 7.6V.
Other features include low start-up
current, pulse-by-pulse current lim-
iting, and a high-current totem pole
output for driving capacitive loads,
such as gate of a power MOSFET.
The output is low in the off state,
consistent with N-channel devices.
Absolute Maximum Ratings
Supply Voltage (ICC<30mA) ..........................................................Self Limiting
Supply Voltage (Low Impedance Source)...................................................30V
Output Current ...............................................................................................±1A
Output Energy (Capacitive Load) .................................................................5µJ
Analog Inputs (VFB, VSENSE)...........................................................-0.3V to 5.5V
Error Amp Output Sink Current...............................................................10mA
Lead Temperature Soldering
Reflow (SMD styles only) ...........60 sec. max above 183°C, 230°C peak
Block Diagram
VCC VCC Undervoltage Lock-out
34V
Gnd
VFB
COMP
OSC
Sense
8.4V/7.6V
Set/ 5.0 Volt
Reset Reference
Error
Amplifier
-
+
2.50V
Oscillator
VREF
R Undervoltage
Lockout
R
Toggle
Flip-Flop
2R
R
S
R
1V
Current PWM
Sensing Latch
Comparator
NOR
Internal
Bias
VCC Pwr
VREF
VOUT
Pwr Gnd
Features
s Optimized for Off-line
Control
s Temperature
Compensated Oscillator
s 50% Maximum Duty-cycle
Clamp
s VREF Stabilized before
Output Stage is Enabled
s Low Start-up Current
s Pulse-by-pulse Current
Limiting
s Improved Undervoltage
Lockout
s Double Pulse Suppression
s 1% Trimmed Bandgap
Reference
s High Current Totem Pole
Output
Package Options
8L SO Narrow
COMP 1
VFB 2
Sense 3
OSC 4
8 VREF
7 VCC
6 VOUT
5 Gnd
14L SO Narrow
COMP 1
NC 2
VFB 3
NC 4
Sense 5
NC 6
OSC 7
14 VREF
13 NC
12 VCC
11 VCC Pwr
10 VOUT
9 Gnd
8 Pwr Gnd
Rev. 3/4/99
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
1
A Company
®




Cherry Semiconductor Corporation

CS52845 Datasheet Preview

CS52845 Datasheet

Current Mode PWM Control Circuit with 50% Max Duty Cycle

No Preview Available !

Electrical Characteristics: -40 TA 85˚C; VCC = 15V (Note 1); RT = 10k; CT = 3.3nF for sawtooth mode.unless otherwise stated.
PARAMETER
s Reference Section
Output Voltage
Line Regulation
Load Regulation
Temperature Stability
Total Output Variation
Output Noise Voltage
Long Term Stability
Output Short Circuit
TEST CONDITIONS
TJ=25˚C, IREF=1mA
12VCC25V
1IREF20mA
(Note 2)
Line, Load, Temp. (Note 2)
10Hzf10kHz, TJ=25˚C (Note 2)
TA=125˚C, 1000 Hrs. (Note 2)
TA=25˚C
MIN
4.95
4.90
-30
TYP
5.00
6
6
0.2
50
5
-100
MAX
5.05
20
25
0.4
5.10
25
-180
UNIT
V
mV
mV
mV/˚C
V
µV
mV
mA
s Oscillator Section
Initial Accuracy
Voltage Stability
Temperature Stability
Amplitude
Sawtooth Mode, TJ=25˚C
12VCC25V
Sawtooth Mode TMINTATMAX
(Note 2)
VOSC (peak to peak)
47 52 57 kHz
0.2 1.0 %
5%
1.7 V
s Error Amp Section
Input Voltage
Input Bias Current
AVOL
Unity Gain Bandwidth
PSRR
Output Sink Current
Output Source Current
VOUT HIGH
VOUT LOW
VCOMP=2.5V
VFB=0V
2VOUT4V
(Note 2)
12VCC25V
VFB=2.7V, VCOMP=1.1V
VFB=2.3V, VCOMP=5V
VFB=2.3V, RL=15kto Gnd
VFB=2.7V, RL=15kto VREF
2.45 2.50 2.55 V
-0.3 -1.0 µA
65 90
dB
0.7 1.0
MHz
60 70
dB
26
mA
-0.5 -0.8
mA
56
V
0.7 1.1 V
s Current Sense Section
Gain
Maximum Input Signal
PSRR
Input Bias Current
Delay to Output
(Notes 3 & 4)
VCOMP=5V (Note 3)
12VCC25V (Note 3)
VSense=0V
TJ=25˚C (Note 2)
2.85 3.00 3.15 V/V
0.9 1.0 1.1 V
70 dB
-2 -10 µA
150 300 ns
s Output Section
Output Low Level
ISINK=200mA
Output High Level
Rise Time
Fall Time
ISINK=20mA
ISOURCE=20mA
ISOURCE=200mA
TJ=25˚C, CL=1nF (Note 2)
TJ=25˚C, CL=1nF (Note 2)
0.1 0.4 V
1.5 2.2 V
13.0 13.5
12.0 13.5
V
V
50 150 ns
50 150 ns
2


Part Number CS52845
Description Current Mode PWM Control Circuit with 50% Max Duty Cycle
Maker Cherry Semiconductor Corporation
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CS52845 Datasheet PDF






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