Datasheet
ADS8634
ADS8638
www.ti.com
SBAS541A –MAY 2011– REVISED AUGUST 2011
PAGE 1 REGISTER DESCRIPTIONS: ADS8638
This section provides bit-by-bit descriptions of each page 1 register. As described earlier, the device registers are
mapped to two pages. Page 0 is selected by default at power-up and after reset. Page 1 can be selected by
writing 01h to register address 7Fh. After selecting page 1, any register read/write action addresses the page 1
registers. Writing 00h to register address 7Fh selects page 0 for any further register operations.
Alarm Threshold Setting Registers for the ADS8638
The ADS8634/8 feature high and low alarms individually for the temperature sensor and each of the eight
channels. Each alarm threshold is 12 bits wide with a 4-bit hysteresis. This 16-bit setting is accomplished through
two 8-bit registers associated with every high/low alarm.
TLA MSB to THA LSB: Temperature Alarm Registers (Address = 00h to 03h; Page 1)
ADDRESS ON
REGISTER PAGE 1 Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
TLA MSB TLA Hysteresis[3:0] TLA[11:8]
TLA LSB TLA[7:0]
THA MSB THA Hysteresis[3:0] THA[11:8]
THA LSB THA[7:0]
THA/LA MSB REGISTER
Bits[7:4] THA/LA Hysteresis[3:0]
These bits set the temperature high/low alarm hysteresis.
0000 = No hyeteresis
0001 = ±1LSB hystetesis
0010 to 1110 = ±2LSB to ±14LSB hystetesis
1111 = ±15LSB hystetesis
Bits[3:0] THA/LA[11:8]
These bits set the MSB nibble for the 12-bit temperature high/low alarm.
For example, the temperature high alarm threshold is AFFh when the THA MSB register (address 02h, page 1)
setting is Ah and the THA LSB register (address 03h, page 1) register setting is FFh.
0000 = MSB nibble is 0h
0001 = MSB nibble is 1h
0010 to 1110 = MSB nibble is 2h to Eh
1111 = MSB nibble is Fh
THA/LA LSB REGISTER
Bits[7:0] THA/LA[7:0]
These bits set the LSB byte for the 12-bit temperature high alarm.
For example, the temperature low alarm threshold is F02h when the TLA LSB register (address 01h) setting is 02h
and the TLS MSB register (address 00h, page 1) register setting is Fh.
0000 0000 = LSB byte is 0h
0000 0001 = LSB byte is 1h
0000 0010 to 1110 1111 = LSB byte is 02h to EFh
1111 1111 = LSB byte is FFh
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