TPS54362-Q1_15 Datasheet, PDF (20/40 Pages) Texas Instruments – TPS54362-Q1 3-A, 60-V Step-Down DC-DC Converter With Low I(q)

TPS54362-Q1
SLVS845G – MARCH 2009 – REVISED AUGUST 2014
f_(p1)
=
2p
´
(C5 + C8)
R6 ´ (C5 ´
C8)
f_(p2)
=
2p
´
1
R9
´
C7
f_(z1)
=
2p
´
1
R6
´
C5
f_(z2) =
2p
´
1
(R4 + R9)
´
C7
7.3.23 Bode Plot of Converter Gain
Open-Loop
Error-Amplifier Gain
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(15)
(16)
(17)
(18)
f_(z1) f_(z2)
f_(p1) f_(p2)
20 log R6 (R4 + R9) / (R4 ´ R9)
20 log (10)
Modulator Gain
20 log (R6 / R4)
Compensation
Gain
Closed-Loop Gain
f_(LC)
f_(ESR)
Frequency - Hz
Figure 21. Bode Plot of Converter Gain
7.4 Device Functional Modes
7.4.1 Low-Power Mode (LPM)
The TPS54362-Q1 device automatically enters low-power mode once the regulation goes into discontinuous
mode. The internal control circuitry for any transition from low-power mode to high-power mode occurs within 5
μs (typical). In low-power mode, the converter operates as a hysteretic controller with the threshold limits set by
V_{(VReg_UV)} = 0.82 × (R1 + R2 +R3 / (R2 + R3) for the lower limit and approximately V_(VReg) for the upper limit. To
ensure tight regulation in the low-power mode, set the R2 and R3 values accordingly.
The device operates with both automatic and digitally controlled low-power mode. The digital low-power mode
can override the automatic low-power mode function by applying the appropriate signal on the LPM pin. The
device goes into active or normal mode for at least 100 μs on the tripping of RST_TH or VREG_UV. Operating in
active mode or normal mode enables all blocks, including the OV function.
Being in LPM disables the OV function.
Active or normal mode: When the device is in DCM with LPM = High or in CCM with LPM = High or Low
LPM: When part is in DCM with LPM = Low
Automatic and Digital
LPM high:
LPM high forces the device to normal mode at fixed frequency, even at light load
current (the device does pulse skipping to keep output voltage in regulation at light
loads).
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