AAT1102 Datasheet, PDF (12/18 Pages) Advanced Analog Technology, Inc. – ADVANCED PWM DC-DC CONVERTER WITH INTERNAL SWITCH AND SOFT-START

Advanced Analog Technology, Inc.
R_c
= ^Vo
V_FB
2πf _ciCR_cs
kg _m
(R_L + 2r_c )
^{(1 −}

D)R_L
−
r
(1− D)^
AAT1102
V_FB is equal to reference voltage,V_REF .
V_REF =1.24V, k is the correct factor, and
k = (6 − 8)
5. The output filter capacitor is chosen so C .
R_L pole cancels R_c . C_c zero
R_cC_c
=
(1
C
−
3)


R_L
2
+
r_c


,
and
C_c
=
C
(1− 3)R_c
 ^RL
²
+
r_c


Example:
V_IN =5V, V_O =9.6V, I_O =250mA, f _s =600 kHz,
V_FB =1.25V, L = 6.8uH , g_m = 105uS , R_cs = 0.275
V/A,
r_L
= 0.1Ω , r_DS
= 0.23Ω , r
C
= 50mΩ ,
k =7
R_F = 1.4Ω , f_ci = 21.4 kHz, C_c =1.3nF, R_c = 27k
Ó¨, C =4.7uF
Fig.5. Bode diagram using Matlab simulation
Fig.4. CH1: PWM waveform, CH2, v _{p− p}
for Vo
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