VDD

Cap

Control

375 nA

CWD

VDD

CWD

CWD

User Programmable

Capacitor to GND

10 NŸ 5HVLVWRU

to VDD

CWD

Unconnected

TPS3851-Q1

TPS3851-Q1

TPS3851-Q1

VDD

VDD

Cap

Control

375 nA

VDD

Cap

Control

375 nA

VDD

Copyright © 2016, Texas Instruments Incorporated

15

TPS3851-Q1

www.ti.com

SBVS286 – MARCH 2017

Product Folder Links: TPS3851-Q1

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Copyright © 2017, Texas Instruments Incorporated

8 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component

specification, and TI does not warrant its accuracy or completeness. TI’s customers are

responsible for determining suitability of components for their purposes. Customers should

validate and test their design implementation to confirm system functionality.

8.1 Application Information

The following sections describe in detail proper device implementation, depending on the final application

requirements.

8.1.1 CWD Functionality

The TPS3851-Q1 features three options for setting the watchdog timer: connecting a capacitor to the CWD pin,

connecting a pullup resistor to VDD, and leaving the CWD pin unconnected. Figure 24 shows a schematic

drawing of all three options. If this pin is connected to VDD through a 10-k

Ω pullup resistor or left unconnected

(high impedance), then the factory-programmed watchdog timeouts are enabled; see the Factory-Programmed

Timing Options section. Otherwise, the watchdog timeout can be adjusted by placing a capacitor from the CWD

pin to ground.

Figure 24. CWD Charging Circuit

8.1.1.1 Factory-Programmed Timing Options

If using the factory-programmed timing options (listed in Table 2), the CWD pin must either be unconnected or

pulled up to VDD through a 10-kΩ pullup resistor. Using these options enables high-precision, 15% accurate

watchdog timing.

Table 2. Factory Programmed Watchdog Timing

INPUT

UNIT

CWD

SET1

MIN

TYP

MAX

NC

0

Watchdog disabled

NC

1

1360

1600

1840

ms

10 kΩ to VDD

0

Watchdog disabled

10 kΩ to VDD

1

170

200

230

ms