I

R

ISET1

50

R

ISENSE1

TPS2320

TPS2321

www.ti.com

SLVS276F – MARCH 2000 – REVISED JULY 2013

SETTING THE CURRENT-LIMIT CIRCUIT-BREAKER THRESHOLD

determine the current limit of the channel, and can be calculated by the following equation:

(2)

The above information and calculation also apply to channel 2. Table 4 shows some of the current sense

resistors available in the market.

Table 4. Some Current Sense Resistors

CURRENT RANGE (A)

PART NUMBER

DESCRIPTION

MANUFACTURER

0 to 1

WSL-1206, 0.05 1%

0.05

Ω, 0.25 W, 1% resistor

1 to 2

WSL-1206, 0.025 1%

0.025

Ω, 0.25 W, 1% resistor

2 to 4

WSL-1206, 0.015 1%

0.015

Ω, 0.25 W, 1% resistor

Vishay Dale

4 to 6

WSL-2010, 0.010 1%

0.010

Ω, 0.5 W, 1% resistor

6 to 8

WSL-2010, 0.007 1%

0.007

Ω, 0.5 W, 1% resistor

8 to 10

WSR-2, 0.005 1%

0.005

Ω, 0.5 W, 1% resistor

UNDERVOLTAGE LOCKOUT (UVLO)

The TPS2320/TPS2321 includes an undervoltage lockout (UVLO) feature that monitors the voltage present on

the VREG pin. This feature will disable both external MOSFETs if the voltage on VREG drops below 2.78 V

(nominal) and will re-enable normal operation when it rises above 2.85 V (nominal). Since VREG is fed from IN1

through a low-dropout voltage regulator, the voltage on VREG will track the voltage on IN1 within 50 mV. While

the undervoltage lockout is engaged, both GATE1 and GATE2 are held low by internal PMOS pulldown

transistors, ensuring that the external MOSFET transistors remain off at all times, even if all power supplies have

fallen to 0 V.

SINGLE-CHANNEL OPERATION

Some applications may require only a single external MOS transistor. Such applications should use GATE1 and

the associated circuitry (IN1, ISENSE1, ISET1, DISCH1). The IN2 pin should be grounded to disable the circuitry

associated with the GATE2 pin.

POWER-UP CONTROL

The TPS2320/TPS2321 includes a 500

μs (nominal) startup delay that ensures that internal circuitry has

sufficient time to start before the device begins turning on the external MOSFETs. This delay is triggered only

upon the rapid application of power to the circuit. If the power supply ramps up slowly, the undervoltage lockout

circuitry will provide adequate protection against undervoltage operation.

3-CHANNEL HOT-SWAP APPLICATION

Some applications require hot-swap control of up to three voltage rails, but may not explicitly require the sensing

of the status of the output power on all three of the voltage rails. One such application is device bay, where dv/dt

control of 3.3 V, 5 V, and 12 V is required. By using Channel 2 to drive both the 3.3-V and 5-V power rails and

Channel 1 to drive the 12-V power rail, as is shown below, TPS2320/01 can deliver three different voltages to

three loads while monitoring the status of two of the loads.

Copyright © 2000–2013, Texas Instruments Incorporated

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