EVAL-ADT7463EB ON Semiconductor, EVAL-ADT7463EB Datasheet - Page 13

• Manufacturer Part Number: EVAL-ADT7463EB
• Manufacturer: ON Semiconductor

Specifications of EVAL-ADT7463EB

• Lead Free Status / RoHS Status: Supplier Unconfirmed

VOLTAGE MEASUREMENT INPUTS
The ADT7463 has four external voltage measurement channels.
It can also measure its own supply voltage, V
Pins 20 to 23 are dedicated to measuring 5 V, 12 V, and 2.5 V
supplies and the processor core voltage V
The V
the V
(Reg. 0x40) allows a 5 V supply to power the ADT7463 and be
measured without overranging the V
The 2.5 V input can be used to monitor a chipset supply voltage
in computer systems.
ANALOG-TO-DIGITAL CONVERTER (ADC)
All analog inputs are multiplexed into the on-chip, successive
approximation, ADC. This has a resolution of 10 bits. The basic
input range is 0 V to 2.25 V, but the inputs have built-in attenu-
ators to allow measurement of 2.5 V, 3.3 V, 5 V, 12 V, and the
processor core voltage V
allow for the tolerance of these supply voltages, the ADC pro-
duces an output of 3/4 full scale (decimal 768 or 300 hex) for
the nominal input voltage and so has adequate headroom to
cope with overvoltages.
INPUT CIRCUITRY
The internal structure for the analog inputs is shown in Figure 13.
Each input circuit consists of an input protection diode, an
attenuator, plus a capacitor to form a first-order, low-pass filter
that gives the input immunity to high frequency noise.
VOLTAGE MEASUREMENT REGISTERS
Reg. 0x20 2.5 V Reading = 0x00 Default
Reg. 0x21 V
Reg. 0x22 V
Reg. 0x23 5 V Reading = 0x00 Default
Reg. 0x24 12 V Reading = 0x00 Default
REV. C
CC
CC
pin (Pin 4). Setting Bit 7 of Configuration Register 1
supply voltage measurement is carried out through
CCP
CC
Reading = 0x00 Default
Reading = 0x00 Default
CCP
without any external components. To
CC
measurement channel.
CCP
CC
(0 V to 3 V input).
.
–13–
VOLTAGE MEASUREMENT LIMIT REGISTERS
Associated with each voltage measurement channel are high and
low limit registers. Exceeding the programmed high or low limit
causes the appropriate status bit to be set. Exceeding either limit
can also generate SMBALERT interrupts.
Reg. 0x44 2.5 V Low Limit = 0x00 Default
Reg. 0x45 2.5 V High Limit = 0xFF Default
Reg. 0x46 V
Reg. 0x47 V
Reg. 0x48 V
Reg. 0x49 V
Reg. 0x4A 5 V Low Limit = 0x00 Default
Reg. 0x4B 5 V High Limit = 0xFF Default
Reg. 0x4C 12 V Low Limit = 0x00 Default
Reg. 0x4D 12 V High Limit = 0xFF Default
Table II shows the input ranges of the analog inputs and output
codes of the 10-bit ADC.
When the ADC is running, it samples and converts a voltage
input in 711 µs and averages 16 conversions to reduce noise;
a measurement on each input takes nominally 11.38 ms.
3.3V
2.5V
12V
V
Figure 13. Structure of Analog Inputs
5V
CCP
CCP
CC
CC
CCP
IN
IN
IN
IN
Low Limit = 0x00 Default
High Limit = 0xFF Default
Low Limit = 0x00 Default
High Limit = 0xFF Default
17.5k
120k
93k
68k
45k
52.5k
20k
47k
71k
94k
30pF
30pF
30pF
30pF
35pF
ADT7463
MUX