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IND(ripple)

OCTRIP

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DS on

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8

TPS51916

www.ti.com

SLUSAE1D – DECEMBER 2010 – REVISED JUNE 2012

The undervoltage protection (UVP) latch is set when the VDDQSNS voltage remains lower than 68% (typ) of the

REFIN voltage for 1 ms or longer. In this fault condition, the controller latches DRVH low and DRVL low and

discharges the VDDQ, VTT and VTTREF outputs. UVP detection function is enabled after 1.2 ms of SMPS

operation to ensure startup.

To release the OVP and UVP latches, toggle S5 or adjust the V5IN voltage down and up beyond the

undervoltage lockout threshold.

VDDQ Out-of-Bound Operation

When the output voltage rises to 8% above the target value, the out-of-bound operation starts. During the out-of-

bound condition, the controller operates in forced PWM-only mode. Turning on the low-side MOSFET beyond the

zero inductor current quickly discharges the output capacitor. During this operation, the cycle-by-cycle negative

overcurrent limit is also valid. Once the output voltage returns to within regulation range, the controller resumes

to auto-skip mode.

VDDQ Overcurrent Protection

The VDDQ SMPS has cycle-by-cycle overcurrent limiting protection. The inductor current is monitored during the

is larger than the overcurrent trip level. The current monitor circuit inputs are PGND and SW pins so that those

should be properly connected to the source and drain terminals of low-side MOSFET. The overcurrent trip level,

has 4700ppm/°C temperature coefficient to compensate the temperature dependency of the low-side MOSFET

(5)

where

•

(6)

In an overcurrent condition, the current to the load exceeds the current to the output capacitor, thus the output

voltage tends to fall down. Eventually, it crosses the undervoltage protection threshold and shuts down.

VTT Overcurrent Protection

The LDO has an internally fixed constant overcurrent limiting of 3-A (typ) for both sink and source operation.

V5IN Undervoltage Lockout Protection

The TPS51916 has a 5-V supply undervoltage lockout protection (UVLO) threshold. When the V5IN voltage is

lower than UVLO threshold voltage, typically 3.9 V, VDDQ, VTT and VTTREF are shut off. This is a non-latch

protection.

Thermal Shutdown

The TPS51916 includes an internal temperature monitor. If the temperature exceeds the threshold value, 140°C

(typ), VDDQ, VTT and VTTREF are shut off. The state of VDDQ is open, and that of VTT and VTTREF are high

impedance (high-Z) at thermal shutdown. The discharge functions of all outputs are disabled. This is a non-latch

protection and the operation is restarted with soft-start sequence when the device temperature is reduced by

10°C (typ).

Copyright © 2010–2012, Texas Instruments Incorporated

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