TCV7104FN

2010-03-23

7

Output Filter Capacitor Selection

Use a low-ESR electrolytic or ceramic capacitor as the output filter capacitor. Since a capacitor is generally

sensitive to temperature, choose one with excellent temperature characteristics. As a rule of thumb, its

capacitance should be 10

μF or greater for applications. The capacitance should be set to an optimal value that

meets the system’s ripple voltage requirement and transient load response characteristics. The phase margin

tends to decrease as the output voltage is getting low. Enlarge a capacitance for output flatness when phase

margin is insufficient, or the transient load response characteristics cannot be satisfied. Since the ceramic

capacitor has a very low ESR value, it helps reduce the output ripple voltage; however, because the ceramic

capacitor provides less phase margin, it should be thoroughly evaluated.

Soft-Start Feature

The TCV7104FN has a soft-start feature.

soft-start time can be calculated as follows:

SS

SS2

C

1

.

0

t

⋅

=

···························· (4)

connected between SS and SGND.

The soft-start feature is activated when the TCV7104FN exits the undervoltage lockout (UVLO) state after

power-up and when the voltage at the EN pin has changed from logic low to logic high.

Overcurrent Protection（OCP）

The TCV7104FN has maximum current limiting. The TCV7104FN limits the ON time of high side switching

Undervoltage Lockout (UVLO)

The TCV7104FN has undervoltage lockout (UVLO) protection circuitry. The TCV7104FN does not provide

Figure 4 Undervoltage Lockout Operation

Soft start

Hysteresis:

Undervoltage lockout

Switching operation

stops

GND

GND

Undervoltage lockout

Switching operation starts