TCN75
DS21490D-page 6 2001-2012 Microchip Technology Inc.
3.0 DETAILED DESCRIPTION
A typical TCN75 hardware connection is shown in
Figure 3-1.
FIGURE 3-1: Typical Application
3.1 Serial Data (SDA)
Bidirectional. Serial data is transferred in both
directions using this pin.
3.2 Serial Clock (SCL)
Input. Clocks data into and out of the TCN75.
3.3 INT/CMPTR
Open Collector, Programmable Polarity. In Comparator
mode, unconditionally driven active any time
temperature exceeds the value programmed into the
T
SET
register. INT/CMPTR will become inactive when
temperature subsequently falls below the T
HYST
set-
ting. (See Section 5.0 “Register Set and Program-
mer’s ModeL”, Register Set and Programmer’s
Model). In Interrupt mode, INT/CMPTR is also made
active by TEMP exceeding T
SET
; it is unconditionally
reset to its inactive state by reading any register via the
2-wire bus. If and when temperature falls below T
HYST
,
INT/CMPTR is again driven active. Reading any regis-
ter will clear the T
HYST
interrupt. In Interrupt mode, the
INT/CMPTR output is unconditionally reset upon enter-
ing Shutdown mode. If programmed as an active-low
output, it can be wire-ORed with any number of other
open collector devices. Most systems will require a
pull-up resistor for this configuration.
Note that current sourced from the pull-up resistor
causes power dissipation and may cause internal heat-
ing of the TCN75. To avoid affecting the accuracy of
ambient temperature readings, the pull-up resistor
should be made as large as possible. INT/CMPTR’s
output polarity may be programmed by writing to the
INT/CMPTR POLARITY bit in the CONFIG register.
The default is active low.
3.4 Address (A2, A1, A0)
Inputs. Sets the three Least Significant bits of the
TCN75 8-bit address. A match between the TCN75’s
address and the address specified in the serial bit
stream must be made to initiate communication with
the TCN75. Many protocol-compatible devices with
other addresses may share the same 2-wire bus.
3.5 Slave Address
The four Most Significant bits of the Address Byte (A6,
A5, A4, A3) are fixed to 1001[B]. The states of A2, A1
and A0 in the serial bit stream must match the states of
the A2, A1 and A0 address inputs for the TCN75 to
respond with an Acknowledge (indicating the TCN75 is
on the bus and ready to accept data). The Slave
Address is represented in Table 3-1.
A
0
A
1
A
2
SDA
SCL
+V
DD
(3V to 5.5V)
Address
(Set as Desired)
I
2
C
™
Interface
C
Bypass
To Controller
0.1 µF Recommended
Unless Device is Mounted
Close to CPU
INT/CMPTR
7
6
5
1
2
3
8
4
TCN75
TABLE 3-1: TCN75 SLAVE ADDRESS
1 0 0 1 A2 A1 A0
MSB LSBS
