Datasheet

LOAD 1

POWER

SUPPLY 1

+12V

GND

MeterV

www.ti.com Setup

3 Setup

3.1 Basic Setup

Figure 1 shows the basic setup for performance bench testing using resistive loads on channel A. Channel

B can be configured the same way as well if dual channel testing is desired. In this set-up, the on board

capacitors (C4–C7) can be used to supply a capacitive load to check the output voltage ramp. A load can

be connected to the output of the TPS2456EVM as shown.

During the output voltage ramp-up, the current drawn from the input power supply is equal to the current

in the resistor plus the current required to charge the capacitance. The total current available for the

resistor and capacitors is fixed by the current limit of the TPS2456 which is set to a nominal 8.36A on the

EVM board. The 8.36A of available current must charge the capacitor and resistor combination up to 12V

before the fault timer expires. The fault timer is set to a nominal 2.97ms on the EVM board. This means

there is a minimum resistance value (maximum current draw) for the load for each selected output

capacitance value. Any lower resistance draws too much current and triggers the fault timer. The minimum

resistance value, based on nominal or typical circuit values, that can be supported is:

Output Capacitance Load Resistance

220 µF >1.43 Ω

440 µF >1.46 Ω

660 µF >1.56 Ω

880 µF >1.78 Ω

Each channel of the TPS2456EVM can be independently enabled. Each channel can also be configured

to latch-off during a fault or to periodically retry starting. The retry and enable functions are configured

using shunts on two pin jumper headers. The functionality of these jumpers is:

J21 J20 Function

OPEN OPEN Channel A Enabled, Latch off on fault

OPEN SHORT Channel A Enabled, Retry on fault

SHORT OPEN Channel A Disabled

SHORT SHORT Channel A Disabled

J23 J22 Function

OPEN OPEN Channel B Enabled, Latch off on fault

OPEN SHORT Channel B Enabled, Retry on fault

SHORT OPEN Channel B Disabled

SHORT SHORT Channel B Disabled

SLVU368–March 2010 TPS2456EVM

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