TMP435
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SBOS495A –MARCH 2010–REVISED APRIL 2010
The LHIGH and RHIGH bit values depend on the
state of the AL/TH bit in the Configuration Register. If
the AL/TH bit is ‘0’, the LHIGH bit reads as ‘1’ if the
local high limit was exceeded since the last clearing
of the Status Register. The RHIGH bit reads as ‘1’ if
the remote high limit was exceeded since the last
clearing of the Status Register. If the AL/TH bit is ‘1’,
the remote high limit and the local high limit are used
to implement a THERM2 function. LHIGH reads as ‘1’
if the local temperature has exceeded the local high
limit and remains greater than the local high limit less
the value in the Hysteresis Register.
Configuration Register 1
Configuration Register 1 sets the temperature range,
controls shutdown mode, and determines how the
ALERT/THERM2 pin functions. This Configuration
Register is set by writing to pointer address 09h and
read by reading from pointer address 03h.
The MASK bit (bit 7) enables or disables the ALERT
pin output if ALERT/THERM2 = 0. If ALERT/THERM2
= 1 then the MASK bit has no effect. If MASK is set to
‘0’, the ALERT pin goes low when one of the
temperature measurement channels exceeds its high
or low limits for the chosen number of consecutive
conversions. If the MASK bit is set to ‘1’, the TMP435
retains the ALERT pin status, but the ALERT pin
does not go low.
The RHIGH bit reads as ‘1’ if the remote temperature
has exceeded the remote high limit and remains
greater than the remote high limit less the value in
the Hysteresis Register.
The shutdown (SD) bit (bit 6) enables or disables the
temperature measurement circuitry. lf SD = 0, the
TMP435 converts continuously at the rate set in the
conversion rate register. When SD is set to '1', the
TMP435 immediately stops converting and enters a
shutdown mode. When SD is set to '0' again, the
TMP435 resumes continuous conversions. A single
conversion can be started when SD = 1 by writing to
the One-Shot Register.
The LLOW and RLOW bits are not affected by the
AL/TH bit. The LLOW bit reads as ‘1’ if the local low
limit was exceeded since the last clearing of the
Status Register. The RLOW bit reads as ‘1’ if the
remote low limit was exceeded since the last clearing
of the Status Register.
The values of the LLOW, RLOW, and OPEN (as well
as LHIGH and RHIGH when AL/TH is ‘0’) are latched
and read as ‘1’ until the Status Register is read or a
device reset occurs. These bits are cleared by
reading the Status Register, provided that the
condition causing the flag to be set no longer exists.
The values of BUSY, LTHRM, and RTHRM (as well
as LHIGH and RHIGH when ALERT/THERM2 is ‘1’)
are not latched and are not cleared by reading the
Status Register. They always indicate the current
state, and are updated appropriately at the end of the
corresponding A/D conversion. Clearing the Status
Register bits does not clear the state of the ALERT
pin; an SMBus alert response address command
must be used to clear the ALERT pin.
The AL/TH bit (bit 5) controls whether the ALERT pin
functions in ALERT mode or THERM2 mode. If ALTH
= 0, the ALERT pin operates as an interrupt pin. In
this mode, the ALERT pin goes low after the set
number of consecutive out-of-limit temperature
measurements occur.
If AL/TH = 1, the ALERT/THERM2 pin implements a
THERM function (THERM2). In this mode, THERM2
functions similar to the THERM pin except that the
local high limit and remote high limit registers are
used for the thresholds. THERM2 goes low when
either RHIGH or LHIGH is set.
The TMP435 NORs, LHIGH, LLOW, RHIGH, RLOW,
and OPEN, so a status change for any of these flags
from ‘0’ to ‘1’ automatically causes the ALERT pin to
go low (only applies when the ALERT/THERM2 pin is
configured for ALERT mode).
The temperature range is set by configuring bit 2 of
Configuration Register 1. Setting this bit low
configures
the
TMP435
for
the
standard
measurement range (0°C to +127°C); temperature
conversions are stored in the standard binary format.
Setting bit 2 high configures the TMP435 for the
extended measurement range (–55°C to +150°C);
temperature conversions are stored in the extended
binary format (see Table 1).
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The remaining bits of Configuration Register 1 are
reserved and must always be set to ‘0’. The power-on
reset value for this register is 00h. Table
summarizes the bits of Configuration Register 1.
5
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