HI-8436

HOLT INTEGRATED CIRCUITS

8

REGISTER DESCRIPTIONS (cont.)

TABLE 7.

DATA WORD 1

Bit

Name

R/W Default

Description

7-6

-

R/W

0

Not Used.

5-0

SOHYS5-0

R/W

0

Supply/Open Hysteresis. For all inputs programmed to be Supply/Open sensors the hysteresis

is set by these 6 bits.

.

DATA WORD 0

7-6

-

R/W

0

Not Used.

5- 0

SOCVAL5-0 R/W

0

Supply/Open Threshold Center Value. For all inputs programmed to be Supply/Open sensors

the center threshold is set by these 6 bits.

.

VTHI = Threshold center value + ½ Hysteresis, Max limit = 5.2V, Min limit = 0.6V

VTLO = Threshold center value - ½ Hysteresis, Max limit = 5.0V, Min limit = 0.4V

Example: Supply/Open sensor with VTHI = 5V and VTLO = 2V:

a) Program SOHYS

Hysteresis = VTHI - VTLO = 0.2V x SOHYS

SOHYS = (5V - 2V)/(0.2V) = 15 LSB

b) Program SOCVAL

Center Value = (VTHI + VTLO)/2= 0.1V x SOCVAL

SOCVAL = (5V + 2V) / (2 x 0.1) = 35 LSB

c) write 0x3C 0x0F 0x23 to SPI

0x3C writes to the Supply/Open Threshold and Hysteresis Registers.

0x0F = 15 LSB x 0.2V/LSB = 3V Hysteresis

0x23 = 35 LSB x 0.1V/LSB = 3.5V Center Value

VTHI = 3.5+½(3)=5V

VTLO=3.5-½(3)=2V

Hysteresis = 0.2V x SOHYS

Center Threshold = 0.1V x SOCVAL

Note: The maximum value for VTHI = 5.2V and the minimum value for VTLO = 0.4V. Also VTHI - VTLO >= 0.2V.

76543210

MSB

LSB

SUPPLY/OPEN THRESHOLD CENTER VALUE AND HYSTERESIS REGISTER: SOCENHYS

Read: SPI Op-code 0xBC

Write: SPI Op-code 0x3C

Reset Value 00

[Opcode, DB1, DB0]

76543210

MSB

LSB

DATA BYTE 1

DATA BYTE 0

X X

X

X