1

VDD

8

RESET

2

CWD

7

WDO

3

MR

6

WDI

4

GND

5

SET1

Not to scale

Thermal

Pad

3

TPS3851-Q1

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SBVS286 – MARCH 2017

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5 Pin Configuration and Functions

DRB Package

3-mm × 3-mm, 8-Pin VSON

Top View

Pin Functions

NAME

NO.

I/O

DESCRIPTION

CWD

2

I

Programmable watchdog timeout input. The watchdog timeout is set by connecting a capacitor between

selection of the preset watchdog timeouts; see the CWD Functionality section.

The TPS3851-Q1 determines the watchdog timeout using either Equation 1 or Equation 2 with standard or

extended timing, respectively.

GND

4

—

Ground pin

MR

3

I

RESET

8

O

operating range, the RESET timeout-counter starts. At completion, RESET goes high. During startup, the

RESET goes low and remains low until the monitored voltage is within the correct operating range (above

SET1

5

I

Logic input. Grounding the SET1 pin disables the watchdog timer. SET1 and CWD select the watchdog

timeouts; see the SET1 section.

VDD

1

I

Supply voltage pin. For noisy systems, connecting a 0.1-μF bypass capacitor is recommended.

WDI

6

I

When the watchdog is not in use, the SET1 pin can be used to disable the watchdog. WDI is ignored when

RESET or WDO are low (asserted) and when the watchdog is disabled. If the watchdog is disabled, WDI

cannot be left unconnected and must be driven to either VDD or GND.

WDO

7

O

WDO goes low (asserts) when a watchdog timeout occurs. WDO only asserts when RESET is high. When

goes low, WDO is in a high-impedance state.

Thermal pad

—

Connect the thermal pad to a large-area ground plane. The thermal pad is internally connected to GND.