Datasheet

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1.058

R 1.33 39.2 10 ƒ 7 ,

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TPS40140

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SLUS660H –SEPTEMBER 2005–REVISED JUNE 2013

5.17 OVERTEMPERATURE

If the temperature of the controller die is detected to be above 155°C, the upper and lower MOSFETs are

turned off and the 5-V regulator, VREG, is turned off. When the die temperature decreases 30°C the

controller performs a normal start up.

5.18 FAULT MASKING OPERATION

If the TRKx pin voltage is externally limited below the 1.4-V threshold, the controller does not respond to

an Undervoltage fault and the PGOOD output remains low. Other fault modes remain operational. The

overcurrent protection continues to terminate PWM cycle every time the threshold is exceeded, but the

hiccup mode is not entered.

5.19 PROTECTION AND FAULT MODES

There are modes of normal operation during start up and shut down as well various fault modes that may

be detected. It is often necessary to know the state of the upper and lower MOSFETs in these modes.

Table xx shows a summary of these modes and the state of the MOSFETs. A description of each mode

follows the table.

Table 5-1. Fault Mode Summary

MODE UPPER MOSFET LOWER MOSFET

Programmable UVLO_CEx = LOW OFF OFF

Power-on reset: fixed UVLO, BP5 < 4.25 V OFF OFF

Overcurrent OFF, hiccup mode OFF, hiccup mode

Output undervoltage OFF, hiccup mode OFF, hiccup mode

Output overvoltage OFF ON

CLKFLT, missing CLKIO at slave OFF OFF

PHSEL voltage > 4 V, or open to ground OFF OFF

Overtemperature OFF OFF

5.20 SETTING THE SWITCHING FREQUENCY

The clock frequency is programmed by the value of the timing resistor connected from the RT pin to

ground. See Equation 6. This equation gives the frequency for an 8-phase system. For a 6-phase system

the frequency is 1 1/3 times higher.

; (6)

is a single phase frequency, kHz. The R

resistor value is expressed in kΩ. See Figure 5-6.

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