AMC80 Datasheet, PDF (14/23 Pages) Texas Instruments – System Hardware Monitor with Two-Wire/SMBus Serial Interface

AMC80
SBOS559 – MAY 2011
www.ti.com
TEMPERATURE MEASUREMENT
The AMC80 ΔV_BE-type temperature sensor, is a ΔΣ ADC that performs 9-bit or 12-bit twos complement
temperature conversions. An 8-bit comparator that compares the readings to the user-programmable hot and
overtemperature setpoints, and hysteresis values is also incorporated into the AMC80.
Temperature data can be read from the Temperature Reading Register (address 27h). Temperature limits can be
read from and written to the Hot Temperature (T_HOT), Hot Temperature Hysteresis (T_{HOT_HYST}), OS Temperature
(T_OS), and OS Temperature Hysteresis (T_{OS_HYST}) Limit Registers (addresses 38h to 3Bh). Each limit is
represented in 12-bit, 9-bit, or 8-bit resolution, as shown in Table 2.
TEMPERATURE
+125°C
+25°C
+1°C
0.0625°C
0°C
–0.0625°C
–1°C
–25°C
–55°C
Table 2. Temperature Lookup
12-BIT DIGITAL OUTPUT (HEX)
LSB = 0.0625°C
07D
019
010
001
000
FFF
FF0
E70
C90
9-BIT DIGITAL OUTPUT (HEX)
LSB = 0.5°C
0FA
032
003
—
000
—
1FF
1CE
192
8-BIT DIGITAL OUTPUT (HEX)
LSB = 1°C
7D
19
01
—
00
—
FF
E7
C9
When using a single-byte read, the eight MSBs of the temperature reading can be found in the Value RAM
Register (address 27h). The remainder of the temperature reading can be found in the OS
Configuration/Temperature Resolution Register (address 06h), bits 4 to 7. In 9-bit format, bit 7 is the only valid
bit. In addition, all nine or 12 bits can be read using a double-byte read at register address 27h.
There are four Value RAM Register limits for the temperature reading that affect the INT and OS outputs of the
AMC80. These are the T_HOT, T_{HOT_HYST,} T_OS, T_{OS_HYST} Limit Registers (addresses 38h to 3Bh); see Table 15.
There are three interrupt modes of operation: Default Interrupt, One-Time Interrupt, and Comparator. The OS
output of the AMC80 can be programmed for One-Time Interrupt mode and Comparator mode. INT can be
programmed for Default Interrupt mode and One-Time Interrupt mode. These modes are explained in the
following subsections.
Default Interrupt Mode
In Default Interrupt mode, exceeding T_HOT causes an interrupt that remains active indefinitely until reset by
reading Interrupt Status Register 1 (address 01h) or cleared by the INT_Clear bit in the Configuration Register
(address 00h, bit 3). When an interrupt event has occurred by exceeding T_HOT, and is then reset, another
interrupt occurs again when the next temperature conversion has completed. The interrupts continue to occur in
this manner until the temperature falls below T_{HOT_HYST}, at which time the interrupt output automatically clears.
One-Time Interrupt Mode
In One-Time Interrupt mode, exceeding T_HOT causes an interrupt that remains active indefinitely until reset by
reading Interrupt Status Register 1 or cleared by the INT_Clear bit in the Configuration Register. When an
interrupt event has occurred by exceeding T_HOT, and is then reset, an interrupt does not occur again until the
temperature falls below T_{HOT_HYST}.
Comparator Mode
In Comparator mode, exceeding T_OS causes the OS output to go low (default) and remain low until the
temperature falls below T_{OS_HYST}. When the temperature falls below T_{OS_HYST}, OS goes high.
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