SE95 PHILIPS [NXP Semiconductors], SE95 Datasheet - Page 8

• Manufacturer Part Number: SE95
• Description: Ultra high accuracy digital temperature sensor and thermal WatchdogE
• Manufacturer: PHILIPS [NXP Semiconductors]

Philips Semiconductors
FUNCTIONAL DESCRIPTION
General operation
The SE95 uses the on-chip band-gap sensor to measure the device
temperature with the resolution of 0.03125 C and stores the 13-bit
2’s complement digital data, resulted from 13-bit A-to-D conversion,
into the device Temp register. This Temp register can be read at any
time by a controller on the I
not affect the conversion in progress during the read operation.
The device can be set to operate in either mode: normal or
shut-down. In normal operation mode, by default, the temp-to-digital
conversion is executed every 100 ms and the Temp register is
updated at the end of each conversion. In shut-down mode, the
device becomes idle, data conversion is disabled and the Temp
register holds the latest result; however, the device I
still active and register write/ read operation can be performed. The
device operation mode is controlled by programming bit B0 of the
configuration register. The temperature conversion is initiated when
the device is powered up or returned to normal mode from
shut-down.
In addition, at the end of each conversion in normal mode, the
temperature data (or Temp) in the Temp register is automatically
compared with the over-temp shut-down threshold data (or Tos)
stored in the Tos register, and the hysteresis data (or Thyst) stored
in the Thyst register, in order to set the state of the device OS output
accordingly. The device Tos and Thyst registers are write/read
capable, and both operate with 9-bit 2’s complement digital data.
To match with this 9-bit operation, the temp register uses only the
9 MSB bits of its 13-bit data for the comparison.
The device temperature conversion rate is programmable and can
be chosen to be one of the four values: 0.125, 1.0, 10, and 30
conversions per second. The default conversion rate is 10
conversions per second. Furthermore, the conversion rate is
selected by programming bits B5 and B6 of the Configuration
Register as shown in Table 3. Note that the average supply current
as well as the device power consumption increase with the
conversion rate.
2004 Dec 21
Ultra high accuracy digital temperature sensor and
thermal Watchdog
2
C-bus. Reading temperature data does
2
C interface is
8
The way that the OS output responds to the comparison operation
depends upon the OS operation mode selected by configuration
bit B1, and the user-defined fault queue defined by configuration
bits B3 and B4.
In OS comparator mode, the OS output behaves like a thermostat. It
becomes active when the Temp exceeds the Tos, and is reset when
the Temp drops below the Thyst. Reading the device registers or
putting the device into shut-down does not change the state of the
OS output. The OS output in this case can be used to control
cooling fans or thermal switches.
In OS interrupt mode, the OS output is used for thermal interruption.
When the device is powered-up, the OS output is first activated only
when the Temp exceeds the Tos; then it remains active indefinitely
until being reset by a read of any register. Once the OS output has
been activated by crossing Tos and then reset, it can be activated
again only when the Temp drops below the Thyst; then again, it
remains active indefinitely until being reset by a read of any register.
The OS interrupt operation would be continued in this sequence:
Tos trip, Reset, Thyst trip, Reset, Tos trip, Reset, Thyst trip, Reset,
and etc. Putting the device into shut-down mode also resets the OS
output.
In both cases, comparator mode and interrupt mode, the OS output
is activated only if a number of consecutive faults, defined by the
device fault queue, has been met. The fault queue is programmable
and stored in the two bits, B3 and B4, of the Configuration register.
Also, the OS output active state is selectable as HIGH or LOW by
setting accordingly the configuration register bit B2.
At power-up, the device is put into normal operation mode, the Tos
is set to 80 C, the Thyst is set to 75 C, the OS active state is
selected LOW and the fault queue is equal to 1. The temp reading
data is not available until the first conversion is completed in about
33 ms.
The OS response to the temperature is illustrated in Figure 11.
Product data sheet
SE95