Datasheet

Gain= A =
mod
VIN
V
ramp
=10
(C5 + C8)
fp1 =
2 R6 (C5 C8)p ´ ´ ´
1
fp2 =
2π × R9 × C7
1
fz1 =
2π × R6 × C5
Modulator Gain
Open Loop Error
Amp Gain
Closed Loop Gain
Compensation
Gain
20 log (10)
20 log (R6/R4)
20 log R6(R4+R9)/(R4*R9)
f
Z2
f
Z1
f
P1
f
P2
f
LC
f
ESR
f - Frequency - Hz
Gain - dB
f
C
TPS54262-Q1
www.ti.com SLVS996C –SEPTEMBER 2009–REVISED JUNE 2010
For VIN = 8 V to 50 V, the VIN/V
ramp
modulator gain is approximately 10 and has a tolerance of about 20%.
(19)
Therefore,
(20)
Also, V
ramp
is fixed for the following range of VIN. V
ramp
= 1 V for VIN < 8 V, and V
ramp
= 5 V for VIN > 48 V.
The frequencies for poles and zeros are given by following equations.
(21)
(22)
(23)
(24)
Guidelines for selecting compensation components selection are provided in the Application Information section
of this document.
Bode Plot of Converter Gain
Figure 29.
Short-Circuit Protection
The TPS54262 features an output short-circuit protection. Short-circuit conditions are detected by monitoring the
RST_TH pin, and when the voltage on this node drops below 0.2 V, the switching frequency is decreased and
current limit is folded back to protect the device. The switching frequency is folded back to approximately 25 kHz
and the current limit is reduced to 30% of the typical current limit value.
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