Datasheet

FS98O22

Rev. 1.6 38/146

4.5. Low Battery Comparator

Figure 4-6 low battery comparator function block

Low Battery Comparator is used for VDD low voltage detection. FS98O22 embeds a voltage divider which can

generate 1/2 VDD and the 1/3 VDD. A multiplexer is used to connect the voltage divides to component input.

The multiplexer’s output is compares with 1.2V. The Control register flags are SILB[1:0] and the ENLB. The

Output flag is LBOUT which is for read only. Please see Figure 4-6.

Table 4-7 low battery comparator register table

Address Name

Referenced

Section

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

Value on Power on

Reset

1CH NETE 4/10/11 ENVS SILB[1:0] ENLB 00000000

1FH SVD 4.5 LBOUT uuuuuuuu

Operation:

1. Operate as Section 4.1 to get the VGG (2 times VDD or external Power Supply).

2. Operate as Section 4.2 to get the VDDA (3.6V)

3. Operate as Section 4.3 to active the Analog Bias Circuit

4. Set SILB to choose the Comparator input. Please see Table 4-8

Table 4-8 low battery comparator voltage detection selection table

SILB [1:0] Detection

oltage if LBOUT = 1

00 1/2 VDD VDD > 2.3 volt

01 1/3 VDD VDD > 3.5 volt

10 AIN AIN > 1.2 volt

5. Set the ENLB register flag, and the Low Battery Comparator is enabled.

6. The output, LBOUT, is the result of the comparator.

FORTUNE'

Properties

For Reference Only