MFS5600AMBA0ES datasheet(48/111 Pages) NXP

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NXP Semiconductors

FS5600

Automotive buck regulator and controller with voltage monitors and watchdog timer

17.6.1 Watchdog impact on PGOOD1/2

When OTP_WD_PGOODx = 1, a watchdog failure causes the PGOODx pin to toggle low

for 10 ms. The watchdog is stopped when PGOODx is low and is reset at the end of the

10 ms.

The FLT_ERR_CNT is incremented by 1 for every PGOODx toggle due to a watchdog

failure.

During the initial 1024 ms window, a single watchdog error (bad refresh or no refresh for

1024ms) is considered a Watchdog failure and the assigned PGOODx pin is toggled.

After the initial 1024 ms window, a 'watchdog failure' when WD_ERR_CNT >=

WD_ERR_LIMIT.

Example behavior: Suppose OTP_WD_PGOODx = 1; if a watchdog error occurs during

the 1024 ms initial period, PGOODx pin is toggled, the FLT_ERR_CNT incremented,

and the watchdog restarted. This allows the system MCU to reset and try refreshing the

watchdog again. If the MCU fails continuously, the FLT_ERR_CNT reaches its limit and

the FS5600 may transition to the deep fail-safe state (if enabled) to prevent a continuous

fault loop. While in the NORMAL STATE, if a watchdog failure occurs (watchdog error

count reaches limit), PGOODx is toggled, FLT_ERR_CNT incremented and the watchdog

restarted. The state machine will return to INIT_RUN state or Deep Fail-Safe based on

the watchdog fault impact settings (independent of PGOODx behavior).

17.7 FS0B pin

The FS0B pin indicates to the system status of the various safety mechanisms being

handled by the FS5600. This includes indication of health of internal circuitry (via ABIST),

a valid watchdog, valid SW1, SW2, VMON1, VMON2, VMON3, and VMON4, valid

ERRMON, valid FCCU, and monitoring of PGOOD1/2.

The FS0B pin is released high in the NORMAL state. It is asserted low in all other states.

The FS0B pin is internally held low when a valid VIN is present with EN1 and EN2 =

Low. It is also asserted low if the VIN pin has a disconnection, provided SW1IN pin is

connected.

FS0B is a global pin, and can be pulled up to VIN if required in the system.

17.7.1 FS0B pin electrical specifications

All parameters are specified at TA = –40 °C to 125 °C, VIN = 12 V, and typical external

component values, unless otherwise noted. Typical values are specified at 25 °C, unless

otherwise noted.

Parameter

Symbol

Min

Typ

Max

Unit

FS0B_VOH (10 kohm pullup to VDDIO)

FS0B_VOH —

—

VDDIO – 0.5

FS0B_VOL(10 kohm pullup to VDDIO)

FS0B_VOL

0.4

—

Table 46. FS0B pin electrical specifications

17.8 PGOOD1, PGOOD2, FS0B stuck at fault check

PGOOD1, PGOOD2, and FS0B pins are continually monitored by digital to catch 'stuck-

at' faults. The output at these pins is compared to the internal digital command in real

time.

FS5600

All information provided in this document is subject to legal disclaimers.

Product data sheet

Rev. 3 — 2 August 2022

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