ADM1026JST ON Semiconductor, ADM1026JST Datasheet - Page 18

• Manufacturer Part Number: ADM1026JST
• Description: IC CNTRL SYS REF/EEPROM 48LQFP
• Manufacturer: ON Semiconductor

Specifications of ADM1026JST

• Rohs Status: RoHS non-compliant
• Function: Hardware Monitor
• Topology: ADC, Comparator, Multiplexer, Register Bank
• Sensor Type: External & Internal
• Sensing Temperature: 0°C ~ 100°C, External Sensor
• Output Type: SMBus™
• Output Alarm: No
• Output Fan: Yes
• Voltage - Supply: 3 V ~ 5.5 V
• Operating Temperature: 0°C ~ 100°C
• Mounting Type: Surface Mount
• Package / Case: 48-LFQFP

easily by making V
analog input, and by adding a third resistor to set the positive
full scale.
Note that R3 has no effect as the input voltage at the device
pin is zero when V
device pin is equal to V
Battery Measurement Input (V
battery to be monitored. This is typically a lithium coin cell
such as a CR2032. The V
voltages greater than 1.5 V (see Figure 14). Typically, the
battery in a system is required to keep some device powered
on when the system is in a powered−off state. The V
measurement input is specially designed to minimize battery
drain. To reduce current drain from the battery, the lower
resistor of the V
whenever a V
current drain on the V
maximum V
battery functions in a system in excess of the expected 10
years. Note that when a V
made, the current drain is reduced to 6 nA typical. Under
normal voltage measurement operating conditions, all
measurements are made in a round−robin format, and each
reading is actually the result of 16 digitally averaged
measurements. However, averaging is not carried out on the
V
therefore reduce the current drain from the battery.
made is calculated by:
BAT
Symmetrical bipolar input ranges can be accommodated
Also, note that R2 has no effect as the input voltage at the
The V
The V
R1
R3
R1
R3
R1
R2
Figure 29. Scaling and Offsetting A
+
+
+
measurement to reduce measurement time and
BAT
BAT
I +
V
V
V
V
f s
f s
f s
input allows the condition of a CMOS backup
OS
BAT
current drain when a measurement is being
100 kW
*
3.0
2.5
* 3.0
* 2.5
BAT
V
BAT
BAT
voltage = 4.0 V), so a CR2032 CMOS
IN
V
measurement is being made. The total
OS
for Bipolar Inputs
IN
= negative full scale.
attenuator is not connected, except
equal to the full−scale voltage of the
for A
for A
OS
T
BAT
T
PERIOD
PULSE
R1
when V
BAT
BAT
IN0
IN6
R2
+V
pin is 80 nA typical (for a
OS
through A
through A
R3
BAT
input is accurate only for
measurement is not being
A
IN(0–9)
IN
)
= positive full scale.
IN5
IN9
IN0
− A
IN9
(eq. 5)
(eq. 8)
http://onsemi.com
(eq. 6)
(eq. 7)
BAT
18
where T
T
typical), and V
V
measurement circuitry was specifically designed with
battery protection in mind. Internal circuitry prevents the
battery from being back−biased by the ADM1026 supply or
through any other path under normal operating conditions.
In the unlikely event of a catastrophic ADM1026 failure, the
ADM1026 includes a second level of battery protection
including a series 3 kW resistor to limit current to the battery,
as recommended by UL. Thus, it is not necessary to add a
series resistor between the battery and the V
battery can be connected directly to the V
improve voltage measurement accuracy.
Reference Output (V
(Pin 24) that can be used to provide a 1.82 V or 2.5 V
reference voltage output. This output is buffered and
specified to sink or source a load current of 2 mA. The
reference voltage outputs 1.82 V if Bit 2 of Configuration
Register 3 (Address 07h) is 0; it outputs 2.5 V when this bit
is set to 1. This voltage reference output can be used to
provide a stable reference voltage to external circuitry such
as LDOs. The load regulation of the V
0.15% for a sink current of 2 mA and 0.15% for 2 mA source
current. There may be some ripple present on the V
output that requires filtering (±4 m V
the recommended circuitry for the V
than 2 mA. For loads in excess of 2 mA, external circuitry,
such as that shown in Figure 32, can be used to buffer the
V
Figure 31. V
PERIOD
BAT
REF
In addition to minimizing battery current drain, the V
Figure 30. Equivalent V
The ADM1026 offers an on−chip reference voltage
For example, when V
Input Battery Protection
output.
PULSE
= time to measure all analog inputs (273 ms
I +
4.5pF
ADM1026
REF
V
100 kW
BAT
= V
BAT
3.0 V
Interface Circuit for V
49.5kΩ
82.7kΩ
BAT
V
input battery protection.
REF
REF
measurement time (711 ms typical),
273 ms
24
711 ms
)
BAT
BAT
10kΩ
= 3.0 V,
Input Protection Circuit
+ 78 nA
3kΩ
REF
3kΩ
MAX
REF
0.1μF
REF
output for loads less
). Figure 31 shows
output is typically
ADC
DIGITAL
CONTROL
Loads < 2 mA
V
BAT
BAT
REF
input; the
input to
(eq. 9)
BAT
REF