ADM1025ARQ-REEL ON Semiconductor, ADM1025ARQ-REEL Datasheet - Page 8

• Manufacturer Part Number: ADM1025ARQ-REEL
• Description: IC MONITOR SYS/VOLT 5CH 16QSOP
• Manufacturer: ON Semiconductor

Specifications of ADM1025ARQ-REEL

• Rohs Status: RoHS non-compliant
• Applications: PC's, PDA's
• Interface: I²C
• Voltage - Supply: 3 V ~ 5.5 V
• Package / Case: 16-QSOP
• Mounting Type: Surface Mount

ADM1025/ADM1025A
When reading data from a register there are two possibilities:
1. If the ADM1025/ADM1025A’s Address Pointer Register
2. If the Address Pointer Register is known to be already at the
NOTES
1. Although it is possible to read a data byte from a data register
2. In Figures 2a to 2c, the serial bus address is shown as the
3. In addition to supporting the Send Byte and Receive Byte
4. If Reset or interrupt functionality is required, the address pin
MEASUREMENT INPUTS
The ADM1025/ADM1025A has six external measurement
inputs, five for voltage and one (two pins) for temperature.
Internal measurements are also carried out on V
on-chip temperature sensor.
value is unknown or not the desired value, it is first necessary
to set it to the correct value before data can be read from the
desired data register. This is done by performing a write to
the ADM1025/ADM1025A as before, but only the data byte
containing the register address is sent, since data should not
be written to the register. This is shown in Figure 2b.
A read operation is then performed consisting of the serial bus
address, R/W bit set to 1, followed by the data byte read from
the data register. This is shown in Figure 2c.
desired address, data can be read from the corresponding
data register without first writing to the Address Pointer
Register, so Figure 2b can be omitted.
protocols, the ADM1025/ADM1025A also supports the Read
Byte protocol (see System Management Bus specifications
Rev. 1.1 for more information).
cannot be strapped to GND, since this would keep the ADD/
RST/INT/NTO pin permanently low.
without first writing to the Address Pointer Register, if the
Address Pointer Register is already at the correct value, it is
not possible to write data to a register without writing to the
Address Pointer Register because the first data byte of a write
is always written to the Address Pointer Register.
default value 01011(A1)(A0), where A1 and A0 are set by
the three-state ADD pin.
SDA
SCL
SDA
SCL
START BY
START BY
MASTER
MASTER
1
0
1
0
1
1
SERIAL BUS ADDRESS BYTE
SERIAL BUS ADDRESS BYTE
0
0
Figure 2c. Reading Data from a Previously Selected Register
Figure 2b. Writing to the Address Pointer Register Only
1
1
FRAME 1
FRAME 1
1
1
A1
A1
CC
A0
A0
and the
R/W
R/W
ADM1025
ADM1025
ACK. BY
ACK. BY
9
9
–8–
D7
D7
1
1
A/D CONVERTER
These inputs are multiplexed into the on-chip, successive-
approximation, analog-to-digital converter. This has a resolution
of eight bits. The basic input range is 0 V to 2.5 V, but the
inputs have built-in attenuators to allow measurement of 2.5 V,
3.3 V, 5 V, 12 V, and the processor core voltage V
any external components. To allow for the tolerance of these
supply voltages, the A/D converter produces an output of
3/4 full scale (decimal 192) for the nominal input voltage and so
has adequate headroom to cope with overvoltages. Table II
shows the input ranges of the analog inputs and output codes of
the A/D converter.
When the ADC is running, it samples and converts an input
every 11.6 ms, except for the external temperature (D+ and D–)
input. This has special input signal conditioning and is averaged
over 16 conversions to reduce noise; a measurement on this
input takes nominally 34.8 ms.
INPUT CIRCUITS
The internal structure for the analog inputs is shown in Figure 3.
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.
D6
D6
ADDRESS POINTER REGISTER BYTE
D5
D5
DATA BYTE FROM ADM1025
Figure 3. Structure of Analog Inputs
V
3.3V
2.5V
12V
CCPIN
5V
D4
D4
IN
IN
IN
IN
FRAME 2
FRAME 2
D3
D3
122.2k
91.6k
62.6k
36.7k
19.6k
111.2k
22.7k
55.2k
82.4k
105k
D2
D2
D1
D1
D0
D0
35pF
25pF
25pF
25pF
10pF
BY MASTER
ADM1025
NO ACK.
ACK. BY
9
9
MUX
STOP BY
MASTER
STOP BY
MASTER
CCP
without
REV. C