MIC284
Micrel, Inc
VDD
TEMPERATURE-TO-DIGITAL
CONVERTER
Functional Diagram
T1
2:1
MUX
Bandgap
Sensor
and
Reference
1-Bit
DAC
Digital Filter
and
Control
Logic
Result
Registers
T_SET & /CRIT
Setpoint
Registers
Temperature
Hysteresis
Registers
A0
2-Wire
Serial Bus
Interface
DATA
CLK
State
Machine
and
Digital
Comparator
Pointer
Register
Configuration
Register
Open-Drain
Output
MIC284
GND
/INT
/CRIT
Functional Description
Pin Descriptions
VDD:
Power supply input. See electrical specifications.
GND:
Ground return for all MIC284 functions.
CLK:
Clock input to the MIC284 from the two-wire serial bus.
The clock signal is provided by the host, and is shared by all
devices on the bus.
DATA:
Serial data I/O pin that connects to the two-wire serial
bus. DATA is bi-directional and has an open-drain output driver.
An external pull-up resistor or current source somewhere in
the system is necessary on this line. This line is shared by
all devices on the bus.
A0:
This inputs sets the least significant bit of the MIC284’s
7-bit slave address. The six most-significant bits are fixed and
are determined by the part number ordered. (See ordering
information table above.) Each MIC284 will only respond to
its own unique slave address, allowing up to eight MIC284s to
share a single bus. A match between the MIC284’s address
and the address specified in the serial bit stream must be
made to initiate communication. A0 should be tied directly
to VDD or ground. See "Temperature Measurement and
Power On" for more information. A0 determines the slave
address as shown in Table 1:
MIC284
6
P a r t N u m be r
MI C 2 8 4 -0
MI C 2 8 4 -1
MI C 2 8 4 -2
MI C 2 8 4 -3
I n p u ts
A0
0
1
0
1
0
1
0
1
MI C 2 8 4 S l a v e A d d r e s s
B ina r y
100 1000
b
1 0 0 1 0 01
b
100 1010
b
1 0 0 1 0 11
b
100 1100
b
1 0 0 1 1 01
b
100 1110
b
1 0 0 1 1 11
b
Hex
48
h
49
h
4A
h
4B
h
4C
h
4D
h
4E
h
4F
h
Table 1. MIC284 Slave Address Settings
/INT:
Temperature events are indicated to external circuitry
via this output. Operation of the /INT output is controlled by
the MODE and IM bits in the MIC284’s configuration register.
See "Comparator and Interrupt Modes" below. This output
is open-drain and may be wire-OR’ed with other open-drain
signals. Most systems will require a pull-up resistor or current
source on this pin. If the IM bit in the configuration register
is set, it prevents the /INT output from sinking current. In
I
2
C and SMBus systems, the IM bit is therefore an interrupt
September 2005
MICREL [ MICREL SEMICONDUCTOR ]
