VIPER28

Pin settings

5/29

3

Pin settings

3.1

Connection diagram

Figure 3.

Connection diagram (top view)

3.2

Pin description

GND

FB

CONT

VDD

DRAIN

DRAIN

BR

EPT

Table 3.

Pin description

N.

Name

Function

1

GND

This pin represents the device ground and the source of the power section.

2VDD

Supply voltage of the control section. This pin also provides the charging

current of the external capacitor during start-up time.

3CONT

Control pin. The following functions can be selected:

1. current limit set point adjustment. The internal set default value of the cycle-

by-cycle current limit can be reduced by connecting to ground an external

resistor.

2. output voltage monitoring. A voltage exceeding 3 V shuts the IC down

reducing the device consumption. This function is strobed and digitally filtered

for high noise immunity.

4FB

Control input for duty cycle control. Internal current generator provides bias

current for loop regulation. A voltage below 0.6 V activates the burst-mode

operation. A level close to 3.3 V means that the device is approaching the

cycle-by-cycle over-current set point.

5

EPT

This pin allows the connection of an external capacitor for the extra power

management. If the function is not used, the pin has to be connected to GND.

7,8

DRAIN

High voltage drain pin. The built-in high voltage switched start-up bias current is

drawn from this pin too.