CM6901_12 Datasheet, PDF (10/15 Pages) Champion Microelectronic Corp. – SLS (SRC/LLC+SR) Controller with 1 FM+2 PWMs

CM6901
SLS (SRC/LLC+SR) Controller with 1 FM+2 PWMs
Light Load PWMING
In a typical Application, low gain configuration accomplished by connecting R_deao1 and R_deao2 in the closed loop
configuration . The gain for the PWM is determined by R_deao1 and R_deao2 where the gain is equal to - R_deao2/
R_deao1. The voltage of VR_set at which the controller goes into FM and PWM simultaneously is equal to :
VRset = D_IN+ × (1+ R_deao1/ R_deao2) - (R_deao1/ R_deao2) × 3 where 3 is the peak voltage of RTCT
Vary in R_set from VR_set to VR_set + 1.75 × R_deao1/ R_deao2 will cause the duty cycle to vary from 50% to 0%
while the frequency will vary propotionally according to 1.75* R_deao1/ R_deao2 where 1.75 is the peak-to-peak
voltage of the RTCT ramp. For proper operation, select R_deao2 value so that the current through R_deao2 {((D_IN+) -
1.2)/ R_deao2} should be less than 5uA.
Vout
Rf1
VFB
+
Rf3
2.5V ^-
FEAO
.
V Tol
Rest2
RSET
Vref
Rdeao1
Rset1
OSC
Vref
RT
CT
Vref
D_IN+
D_IN-
Rdeao2
-
DEAO
.
-
+
+
RTCT
.
PWM
2012/05/09 Rev2.0
Champion Microelectronic Corporation
Page 10