Technical Reference Notes

APC12 Centauri II

MODEL: APC12 SERIES

SHEET 9 OF 23

JANUARY 6, 2002 REVISION A (PRELIMINARY)

Enable Pin (Standard configuration)

Pin P5 is functioned to enable the output voltage of a

module. If this pin is left open or connected to ≥ 4.1Vdc

up to 14Vdc, the module is turned on. On the other hand,

if this pin is connected to ground or to a voltage potential

from 0 to 0.8Vdc, the module is turned off. The enable pin

can source current up to 60

µA max - suited for typical

open-collector transistors readily available in the market.

For TTL compatibility, Figure 3 shows a 7405 open

collector inverter IC utilized to function the Enable

feature. Other common chips that can do the function are

74S05; 74HCT05; non-inverting - 7407; 74S07; 74HC07.

If SMT packaging is preferred, Fairchild's Tiny Logic

NC7SZ05 or TI's Little Logic SN7SLVC1G06 comes in SOT23

or SC70 packages.

Special Feature Pins (Options):

Trim Function (-9):

Pin P4 is used for output voltage adjustment. The output voltage can be trimmed through an external resistor or through an

external DC supply as described in the succeeding sections.

Method 1: External Trim Resistor.

By connecting an external resistor across P4 and P3 (Gnd), the voltage appearing on pin P2 (Vo) is adjusted to a higher value.

The output voltage of a module can be adjusted up to a maximum value of 3.3V (nominal) or 83% of the input voltage,

whichever is lower. By connecting an external resistor across P4 and P2, Vo is adjusted to a lower value. Only small

reductions, 2%, in voltage are recommended, as adjustment to lower voltages tends to affect the loop compensation of the

module.

Full range adjustment (from 0.9V to 3.6V) can be obtained from a module with the lowest Vo setpoint (0.9Vo).

Figure 3. Output Voltage Enable function diagram.