AD7280AWBSTZ Analog Devices Inc, AD7280AWBSTZ Datasheet - Page 23

• Manufacturer Part Number: AD7280AWBSTZ
• Description: IC BATT MON LI-ION AUTO 48LQFP
• Manufacturer: Analog Devices Inc
• Series: -r

Specifications of AD7280AWBSTZ

• Function: Battery Monitor, Over/Under Voltage Protection
• Battery Chemistry: Lithium-Ion (Li-Ion)
• Voltage - Supply: 8 V ~ 30 V
• Operating Temperature: -40°C ~ 105°C
• Mounting Type: Surface Mount
• Package / Case: 48-LQFP
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

AUXILIARY ADC INPUTS
The AD7280A provides six single-ended analog inputs to the
ADC—AUX1 to AUX6—which can be used to convert the
voltage output of a thermistor temperature measurement circuit.
In the event that no temperature measurements are required or
that individual cell temperature measurements are not required,
the auxiliary ADC inputs can be used to convert any other 0 V
to 5 V input signal.
The AD7280A can be programmed to complete conversions on
all six auxiliary ADC channels, on three auxiliary ADC channels
(AUX1, AUX3, and AUX5), or on none of the auxiliary ADC
input channels. The number of conversions is programmed
through Bits[D15:D14] of the control register. The number of
conversion results supplied by the AD7280A for readback by
the DSP/microprocessor is programmed through Bits[D13:D12]
of the control register. It is also possible to read back a single
auxiliary ADC conversion result from each device in the daisy
chain. This can be done by programming the read register on
each device to read back the required conversion result (see
Example 4 in the Examples of Interfacing with the AD7280A
section). If the device is used in this mode, the overall conversion
sample rate should be limited by the conversion window required
for the number of channels selected by Bits[D15:D14] of the
control register.
In an application where the alert function is used but only one
or two auxiliary ADC inputs are required, the AD7280A should
first be programmed to complete and read back only three
auxiliary ADC conversions by setting Bits[D15:D12] of the
control register to 0101. Channel AUX5 and Channel AUX3 can
be removed from the alert detection by writing to Bits[D1:D0]
of the alert register (see Table 12 in the Alert Output section).
Thermistor Termination Input
If thermistor circuits are used to measure each individual cell
temperature, the thermistor termination pin, AUX
used to terminate the thermistor inputs for each auxiliary ADC
input measurement. This reduces the termination resistor
requirement from six resistors to one. Bit D3 in the control
register should be set to 1 when using the AUX
Note that, due to settling time requirements, the thermistor termi-
nation resistor option should only be used when the acquisition
time of the AD7280A is set to its highest value (1.6 μs). The
acquisition time is configured by setting Bits[D6:D5] of the
control register (see Table 9).
In Figure 36, the termination resistor is placed between V
and AUX
thermistor inputs to the high or low voltage of the thermistor
circuit.
TERM
. The AUX
TERM
input can be used to terminate the
TERM
TERM
input.
, can be
SS
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POWER REQUIREMENTS
The current consumed by the AD7280A in normal operation,
that is, when not in power-down mode, is dependent on the
mode in which the part is being operated. The three distinct
modes of operation can be described as follows:
•
•
•
The AD7280A consumes its highest level of current while con-
verting voltage and/or auxiliary ADC inputs to digital outputs.
Depending on the configuration of the AD7280A, the conversion
time can be as little as 6 μs. The typical current required by the
AD7280A during conversion is 6.9 mA (see Table 2).
When configuring a chain of AD7280As or when reading back
the voltage and/or auxiliary ADC conversion results from a chain
of AD7280As, the current required for each AD7280A is typically
6.5 mA (see Table 2). The time required to read back the voltage
conversions results from 48 lithium ion cells depends on the
speed of the interface clock used, that is, SCLK, but it can be as
low as 1.54 ms.
The typical current consumed by the AD7280A when the cell
balance outputs are switched on is 6.4 mA (see Table 2). The
length of time for which the cell balance outputs are switched
on is defined by the user.
When the AD7280A is not being used in any of the aforemen-
tioned modes of operation, it is recommended that the device
be powered down, as described in the Power-Down section.
This significantly reduces the current drawn by each AD7280A
in the chain, which avoids unnecessary draining of the lithium
ion cells and aids in current matching between devices across
the full battery stack.
Figure 36. Typical Circuit Using the Thermistor Termination Resistor
Voltage and auxiliary ADC input conversion
AD7280A configuration and data readback
Cell balancing
AD7280A
V
REG
AUX
AUX1
AUX2
AUX3
AUX4
AUX5
AUX6
TERM
V
SS
R
TERM
AD7280A