Rev 1.6

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09/2016

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PI3749-x0

Fault Monitoring

The fault bits in the FLT2 and FLT3 registers are only latched when the regulator first stops operating due to a given fault type. If the

regulator is already not operating (perhaps due to a fault protection or being disabled) then should a new fault condition occur, the fault bit

associated with the new fault will not be registered.

Both versions of the PI3749-x0 will auto recover from any fault protection mechanism, once the fault is corrected. However in order to aid in

monitoring of the regulator via the I2C fault monitoring registers, when a fault occurs, the associated fault bit(s) will set and latch until they

A write to the FLTREG_CLR register address will clear all latched fault register bits.

Register

Name

Register

Address

Bit <7>

Bit <6>

Bit <5>

Bit <4>

Bit <3>

Bit <2>

Bit <1>

Bit <0>

FLT2

2

TRISE

OTP

VOUT_NEG

VOUT_OV

EAIN_HI

VIN_OV

VIN_UV

VCC_UV

FLT3

3

0

0

0

0

Q1_FIL

Q3_SIL

Q3_FIL

SLOW_IL

FLTREG_CLR

4

Write only, data ignored

Table 4 — PI3749-20 Fault Readback/Clear Registers

Fault Bit

Name

Fault Bit

Location

Fault Destination

TRISE

FLT2, Bit<7>

Overtemperature Protection: The predicted maximum hot-spot temperature, based on measured temperature and loading,

exceeded the maximum safe operating temperature.

OTP

FLT2, Bit<6>

Overtemperature Protection: The internal measured temperature exceeded the maximum safe operating temperature.

VOUT_NEG

FLT2, Bit<5>

VOUT_OV

FLT2, Bit<4>

Output Overvoltage protection.

EAIN_HI

FLT2, Bit<3>

Current Limit: Overload Timeout.

VIN_OV

FLT2, Bit<2>

Input Overvoltage Lockout.

VIN_UV

FLT2, Bit<1>

Input Undervoltage Lockout.

VCC_UV

FLT2, Bit<0>

Q1_FIL

FLT3, Bit<3>

Current Limit: Fast current limit (Q1) The peak current through Q1 and the inductor was higher than

the maximum current allowed.

Q3_SIL

FLT3, Bit<2>

Current Limit: Slow current limit (Q3)

Q3_FIL

FLT3, Bit<1>

Current Limit: Fast current limit (Q3) The peak current through Q3 and the inductor was higher than

the maximum current allowed.

SLOW_IL

FLT3, Bit<0>

Current Limit: Slow current limit.

Register

Name

Register

Address

Readback

capable?

Bit <3>

Bit <2>

Bit <1>

Bit <0>

MRGN

5

Yes

MRGN_ENA

MRGN<2>

MRGN<1>

MRGN<0>

Table 6 — PI3749-20 Parameter Programming Volatile Registers

Table 5 — Fault register bit summary