EL7563

FN7296 Rev 2.00

Page 11 of 16

May 13, 2005

Reference

A 1.5% temperature compensated bandgap reference is

as the dominant pole of the amplifier and can be increased

in size to maximize transient noise rejection. A value of

0.1µF is recommended.

Oscillator

The system clock is generated by an internal relaxation

oscillator with a maximum duty-cycle of approximately 95%.

or can be driven by an external source. If the oscillator is

driven by an external source care must be taken in selecting

gain of the system.

When external synchronization is required, always choose

lower than that of sync source to accommodate component

and temperature variations. Figure 22 shows a typical

connection.

Junction Temperature Sensor

An internal temperature sensor continuously monitors die

temperature. In the event that die temperature exceeds the

thermal trip-point, the system is in fault state and will be shut

down. The upper and low trip-points are set to 135°C and

115°C respectively.

The VTJ pin is an accurate indication of the internal silicon

junction temperature (see performance curve.) The junction

relation:

Where VTJ is the voltage at VTJ pin in volts.

Power Good and Power On Reset

During power up the output regulator will be disabled until

hysteresis is present to eliminate noise-induced

oscillations.

Under-voltage and over-voltage conditions on the regulator

output are detected through an internal window comparator.

A logic high on the PG output indicates that the regulated

output voltage is within about +10% of the nominal selected

output voltage.

2

3

16

15

14

13

5

6

7

12

11

9

8

10

19

18

EL7563

1

20

EXTERNAL

OSCILLATOR

BAT54S

100pF

390pF

FIGURE 22. OSCILLATOR SYNCHRONIZATION

75 1.2 VTJ

–

0.00384

-------------------------

+

=