ADP1055ACPZ-R7 datasheet(39/140 Pages) AD

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Data Sheet

ADP1055

Rev. A | Page 39 of 140

FAULT RESPONSES AND STATE MACHINE MECHANICS

When a potentially abnormal condition occurs in the power

supply that is regulated by the ADP1055, a flag is asserted and

the system waits for a programmed debounce time. If the flag is

continuously asserted until the end of the debounce time, it is

latched as a fault. The fault is then processed according to the

programmed fault response setting. The fault is cleared only when

the flag condition is removed. The debounce circuitry is reset when

the flag condition is removed; until then the fault remains set.

PRIORITY OF FAULTS

The response to each fault is configurable and is based on a priority

level (see Table 7). A higher number indicates a higher priority.

Table 7. Priority of Faults

Priority

Fault and Configured Fault Response

12 (highest)

Voltage fault: disable output

Voltage fault: shutdown with no retry

Current fault: shutdown with no retry

Voltage fault: shutdown with limited retry

Current fault: shutdown with limited retry

Voltage fault: shutdown with unlimited retry

Current fault: shutdown with unlimited retry

Voltage fault: wait delay and shutdown with

limited or unlimited retry

Current fault: constant current with wait delay

Current fault: constant current without tripping

VOUT_LV

Current fault: constant current mode

1 (lowest)

Voltage fault: ignore fault

FLAGS

The ADP1055 has an extensive set of flags that are set when

certain limits, conditions, and thresholds are exceeded. The

response to these flags is individually programmable. Flags can

be ignored or used to trigger actions such as turning off certain

PWM outputs or entering constant current mode. Flags can also

be used to turn off the power supply. The ADP1055 can be pro-

grammed to respond when these flags are reset.

The ADP1055 also has a set of latched fault registers (Register

0xFE8C to Register 0xFE93). The latched fault registers have the

same flags as the PMBus STATUS_x commands (Register 0x7A

to Register 0x80), but the flags in the latched registers remain set

so that intermittent faults can be detected. The CLEAR_FAULTS

command (Register 0x03) clears the latched fault registers and

resets all the flags.

FIRST FAULT ID (FFID)

The first fault ID (FFID) information is used to capture the first

fault that caused the system to shut down. Register 0xFE95 contains

the ID of the first fault that caused the system to shut down. Faults

captured in the first fault ID register have configured actions of

shutdown immediate, shutdown with retries, and disable PWM

outputs with watchdog timeout. The contents of Register 0xFE95

cannot be overwritten unless the information is first cleared.

The FFID can be cleared by the CLEAR_FAULTS command

(Register 0x03), by a power cycle of the device, or by a PSON

signal using Register 0x01, Register 0x02, or both. If the black

box feature is enabled, the FFID can also be cleared when the

information is saved into the black box.

Table 8. Example First Fault ID Scenarios

Test Setup

Condition

Result

OCP has retry/delay of 100 ms

with Priority 10, debounce = 0.

OVP has retry/delay of 200 ms

with Priority 9, debounce = 0.

OCP occurs at t = 0.

OVP occurs at t = 10 ms.

OCP fault is processed due to smaller debounce time (no retry time), as

well as higher priority.

OCP has retry/delay of 100 ms

with Priority 10, debounce = 0.

OVP has retry/delay of 0 ms with

Priority 11, debounce = 0.

OCP occurs at t = 0.

OVP occurs at t = 10 ms.

OCP fault is processed at t = 0; device waits 100 ms before action is taken.

OCP fault is replaced by OVP, and then OVP fault is processed at t = 10 ms

due to higher priority even though retry delay is larger.

OCP has retry/delay of 100 ms

with Priority 8, debounce = 5 ms.

OVP has retry/delay of 200 ms

with Priority 9, debounce = 100 ms.

OCP occurs at t = 50 ms.

OVP occurs at t = 0.

OVP is registered as a fault at t = 100 ms. OCP is registered as a fault at

t = 55 ms. However, at t = 100 ms, OCP loses priority and OVP is processed

due to higher priority. Exception: If delay of OCP was smaller (for example,

5 ms), then OCP action is processed.

OCP has retry/delay of 100 ms

with Priority 8, debounce = 0.

OVP has retry/delay of 200 ms

with Priority 7, debounce = 0.

OCP occurs at t = 0.

OVP occurs at t = 0.

OCP fault is processed due to higher priority.

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