1

VDD

8

RESET

2

CWD

7

WDO

3

MR

6

WDI

4

GND

5

SET1

Not to scale

Thermal

Pad

3

TPS3851

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SBVS300 – NOVEMBER 2016

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5 Pin Configuration and Functions

DRB Package: TPS3851

3-mm × 3-mm VSON-8

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 this pin and

watchdog timeouts; see the CWD Functionality section.

The TPS3851 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

RESET timeout-counter starts. At completion, RESET goes high. During startup, the state of RESET is undefined

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

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

impedance state.

Thermal pad

—

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