CS2841B Datasheet, PDF (7/10 Pages) Cherry Semiconductor Corporation – Automotive Current Mode PWM Control Circuit

CS2841B
ǒ Ǔ tc + RTCT ln
VREF * Vlower
VREF * Vupper
ǒ Ǔ td + RTCT ln
VREF * IdRT * Vupper
VREF * IdRT * Vlower
Substituting in typical values for the parameters in the
above formulas:
VREF + 5.0 V
Vupper + 2.7 V
Vlower + 1.0 V
Id + 8.3 mA
tc [ 0.5534RTCT
ǒ Ǔ td + RTCT ln
2.3 * 0.0083RT
4.0 * 0.0083RT
The frequency and maximum duty cycle can be
determined from the Typical Performance Characteristic
graphs.
Grounding
High peak currents associated with capacitive loads
necessitate careful grounding techniques. Timing and
bypass capacitors should be connected close to GND pin in
a single point ground.
The transistor and 5.0 kW potentiometer are used to
sample the oscillator waveform and apply an adjustable
ramp to Sense.
VPR
GND
Q1
2n4401
C1
68 mF
C2
68 mF
C3
4.7 pF
100 V
R1
4.7 k
MURS120T3
D1
DZ1
13 V
1N5243B
20T
R2
47
D2 MBR360
C4
9T
0.1 mF
L1 2.2 mH
C5
C6
1000 mF 1000 mF
C7
V_CC
0.1 mF
V_CC−GND
V_CC = 5.0 V @ 750 mA
C8
10 mF
C10
0.1 mF
R5
2.0 k
VC
C9
0.1 mF
V_CC
PV_CC
V_REF
V_OUT
CS2841B
SENSE
R3
4.99 k
1.0 %
R4
C12 ₁₀
10 nF
OSC
GND
C13
4.7 nF
COMP
PGND ^VFB
R8
4.99 k
1.0 %
R7 C11
22.1 k _{0.33 mF}
C14
47 pF
Q2
MTDISN06VTL4
R6
1.0 k
R9
0.2
1.0 %
Figure 8. Flyback Application
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