AAT1164 Datasheet, PDF (17/24 Pages) Advanced Analog Technology, Inc. – TRIPLE-CHANNEL TFT LCD POWER SOLUTION

Advanced Analog Technology, Inc.
April 2007
AAT1164/AAT1164B/AAT1164C
V_RIPPLE (C_OUT )
≈
I_OD
f_S C_OUT
β
V_RIPPLE (ESR) ≈ I_L(peak)r_C
I_C(rms)
=
V_O
R_L
D ₊ D _[(1− D)R_{L ]2}
1− D 12 Lf_S
( )²
P_ESR = I_C(rms) r_C
ESR: Equivalent Series Resistance
Figure 4. Closed-Current Loop for Boost with PCM
Example 2: C_OUT = 38µF, r_C = 20 mΩ
V_RIPPLE (C_OUT ) = 4.1mV
V_RIPPLE (ESR) = 21.5mV
V_RIPPLE = 25.6mV
I_C(rms) = 0.411A
+
+
−
−
P_ESR = 0.00338W or 0.08% power loss
Boost Converter Power loss
The largest portions of power loss in the boost
converter are the internal power MOSFET, the inductor,
the Schottky diode, and the output capacitor. If the
boost converter has 90% efficiency, there is
approximately 7.89% power loss in the internal
MOSFET, 1.34% power loss in the inductor, 0.68%
power loss in the Schottky diode, and 0.08% power loss
in the output capacitor.
Loop Compensation Design
The voltage-loop gain with current loop closed sets the
stability of steady state response and dynamic
performance of transient response. The loop
compensation design is as follows:
−^β
+
Figure 5. Block Diagram of Boost Converter with
Peak Current Mode (PCM)
Power Stage Transfer Functions
The duty to output voltage transfer function T_p is:
T_p (s) =
V_O
d
=
T_p0
(s + ω_esr )(s
s² + 2ξω_ns
−
+
ω_z2
ω_n2
)
Where T_p0
=
V_O
−r_C
(1− D)(R_L
+ r_C )
, ω_esr
=
1
C_OUTr_C
And
ω_z2
=
R_L
(1− D)²
L
−r
, ω_n
=
(1− D)² R_L + r
LC_OUT (R_L + r_C )
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