MCP98243 Datasheet, PDF (26/62 Pages) Microchip Technology – Memory Module Temperature Sensor w/ EEPROM for SPD

MCP98243
5.1.4 AMBIENT TEMPERATURE
REGISTER (T_A)
The MCP98243 uses a band gap temperature sensor
circuit to output analog voltage proportional to absolute
temperature. An internal ΔΣ ADC is used to convert the
analog voltage to a digital word. The converter
resolution is set to 0.25 °C + sign (11-bit data). The
digital word is loaded to a 16-bit read-only Ambient
Temperature register (T_A) that contains 11-bit
temperature data in two’s complement format.
The T_A register bits (bits 12 thru 0) are double-buffered.
Therefore, the user can access the register while, in the
background, the MCP98243 performs an analog-to-
digital conversion. The temperature data from the ΔΣ
ADC is loaded in parallel to the T_A register at t_CONV
refresh rate.
In addition, the T_A register uses three bits (bits 15, 14
and 13) to reflect the Event pin state. This allows the
user to identify the cause of the Event output trigger
(see Section 5.2.3 “Event Output Configuration”);
bit 15 is set to ‘1’ if T_A is greater than or equal to T_CRIT,
bit 14 is set to ‘1’ if T_A is greater than T_UPPER and bit 13
is set to ‘1’ if T_A is less than T_LOWER.
The T_A register bit assignment and boundary
conditions are described in Register 5-5.
REGISTER 5-5: AMBIENT TEMPERATURE REGISTER (T_A) → ADDRESS ‘0000 0101’b (NOTE 1)
R-0
R-0
R-0
T_A vs. T_CRIT T_A vs. T_UPPER T_A vs. T_LOWER
bit 15
R-0
SIGN
R-0
2⁷ °C
R-0
2⁶ °C
R-0
2⁵ °C
R-0
2⁴ °C
bit 8
R-0
2³ °C
bit 7
R-0
2² °C
R-0
2¹ °C
R-0
2⁰ °C
R-0
2^-1 °C
R-0
2^-2 °C
R-0
2^-3 °C
R-0
2^-4 °C
bit 0
Legend:
R = Readable bit
-n = Value at POR
W = Writable bit
‘1’ = Bit is set
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared
x = Bit is unknown
bit 15
bit 14
bit 13
bit 12
bit 11-0
T_A vs. T_CRIT ⁽¹⁾ Bit:
0 = T_A < T_CRIT
1 = T_A ≥ T_CRIT
T_A vs. T_UPPER ⁽¹⁾ Bit:
0 = T_A ≤ T_UPPER
1 = T_A > T_UPPER
T_A vs. T_LOWER ⁽¹⁾ Bit:
0 = T_A ≥ T_LOWER
1 = T_A < T_LOWER
SIGN Bit:
0 = T_A ≥ 0°C
1 = T_A < 0°C
Ambient Temperature (T_A) Bits: (Note 2)
12-bit Ambient Temperature data in two’s complement format.
Note 1: Bits 15, 14 and 13 are not affected by the status of the Event output configuration (bits 5 to 0 of CONFIG)
(Register 5-3).
2: Bits 2, 1, and 0 may remain clear '0' depending on the status of the resolution register (Register 5-8).
The Power-up default is 0.25°C/bit, bits 1 and 0 remain clear '0'.
DS22153B-page 26
© 2009 Microchip Technology Inc.