Datasheet

ADT7302
Rev. B | Page 10 of 16
DIGITAL OUTPUT
–40°C
–0.03125°C
–30°C
11, 1111, 1111, 1111
11, 1100, 0100, 0000
11, 1011, 0000, 0000
TEMPERATURE (°C)
75°C
150°C
01, 0010, 1100, 0000
00, 1001, 0110, 0000
00, 0000, 0000, 0001
04662-013
Figure 13. Temperature to Digital Transfer Function
SCLK
DOUT
DIN
POWER-
DOWN
LEADING ZEROS
DB13 DB0
1
2 3 4
15
16
t
1
t
2
t
3
t
4
t
6
t
5
t
7
t
8
DB12
DB1
DB0
CS
04662-014
Figure 14. Serial Interface Timing Diagram
SERIAL INTERFACE
The serial interface on the ADT7302 consists of four wires:
CS
,
SCLK, DIN, and DOUT. The interface can be operated in
3-wire mode with DIN tied to ground, in which case the inter-
face has read-only capability, with data being read from the data
register via the DOUT line. It is advisable to always use
CS
to
create a communications window, as shown in
Figure 13,
because this improves synchronization between the ADT7302
and the master device. The DIN line is used to write the part
into standby mode, if required. The
CS
line is used to select the
device when more than one device is connected to the serial
clock and data lines.
The part operates in slave mode and requires an externally
applied serial clock to the SCLK input to access data from the
data register. The serial interface on the ADT7302 allows the
part to be interfaced to systems that provide a serial clock
synchronized to the serial data, such as the 80C51, 87C51,
68HC11, 68HC05, and PIC16Cxx microcontrollers as well as
DSP processors.
A read operation from the ADT7302 accesses data from the
temperature value register while a write operation to the part
writes data to the control register.
Read Operation
Figure 14 shows the timing diagram for a serial read from the
ADT7302. The
CS
line enables the SCLK input. Thirteen bits of
data plus a sign bit are transferred during a read operation.
Read operations occur during streams of 16 clock pulses. The
first two bits out are leading zeros and the next 14 bits contain
the temperature data. If
CS
remains low and 16 more SCLK
cycles are applied, the ADT7302 loops around and outputs the
two leading zeros plus the 14 bits of data that are in the temper-
ature value register. When
CS
returns high, the DOUT line goes
into three-state. Data is clocked out onto the DOUT line on the
falling edge of SCLK.