MAX11068EVKIT+ Maxim Integrated Products, MAX11068EVKIT+ Datasheet - Page 30

• Manufacturer Part Number: MAX11068EVKIT+
• Description: KIT SMART BATT MEASUREMENT 12CH
• Manufacturer: Maxim Integrated Products

Specifications of MAX11068EVKIT+

• Main Purpose: Power Management, Battery Monitor, Car
• Utilized Ic / Part: MAX11068
• Primary Attributes: Monitors Current, Voltage, Temperature
• Secondary Attributes: 1 ~ 12 Cell- Li-Ion, 1 ~ 12 Cell- NiMH
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Embedded: -

12-Channel, High-Voltage Sensor, Smart
Data-Acquisition Interface
The DCIN pin is the input to the linear regulator. For
maximum performance, it should be protected from any
overvoltage conditions and also properly decoupled for
peak transient current demands of the linear regulator.
Figure 24 shows a recommended protection and decou-
pling circuit.
Since the linear regulator must supply load peaks to the
ADC and other low-voltage circuitry, the DCIN pin must
be properly decoupled to ensure proper performance. A
1FF high-voltage, high-quality ceramic capacitor should
be used at the pin. The series diode, D1, prevents dis-
charge of the DCIN decoupling capacitor during nega-
tive transients.
During regenerative braking conditions, a surge voltage
is produced by the electric motor. The MAX11068 is
designed to tolerate an absolute maximum of 80V under
this condition. The MAX11068 should be protected
against higher voltages with an external voltage sup-
pressor such as the SMCJ70A. This protection circuit
also helps to reduce power spikes that can occur during
the insertion of the battery cells.
The MAX11068 incorporates a precision, low-temper-
ature coefficient, internal-voltage reference. The refer-
ence is used in the MAX11068 to set the full-scale range
of the ADC. The REF pin is not designed to drive any
external loads, and should be configured with an exter-
nal 1FF capacitor to AGND only. This capacitor should
be mounted as close as possible to the REF pin.
Figure 24. DCIN Overvoltage Protection and Decoupling
Circuit
30
CELL STACK
TOP OF
DCIN Pin Application Circuit
R
22I
22I
LIMIT
NOTE: SEE THE APPLICATION CIRCUIT DIAGRAM
FOR THE PROPER KELVIN-CONNECTION LOCATION.
Precision Internal-
Voltage Reference
C
DCIN
1FF
80V
100kI
SMCJ70
TO GND
INPUT
TO DCIN
INPUT
U
The auxiliary analog inputs (1 and 2) can be used to
monitor analog voltages with a full-scale range of 0 to
THRM (3.4V). The full-scale range of the ADC for the
auxiliary channel measurements is the THRM pin voltage
referenced to AGND. The AUXIN1/2 pins are single-end-
ed inputs that are measured against the AGND pin. A
scan of the AUXIN inputs is first configured by enabling
conversion of one or both inputs through the AIN1EN
and AIN2EN bits of the ADCCFG register (address
0x08). After enabling the channels for measurement,
a scan is initiated by setting the SCAN bit of the
SCANCTRL register to 1. Conversions on the enabled
auxiliary channels commence after the conversions for
the cell input channels are complete. Conversion results
are available in the AIN1 and AIN2 registers (addresses
0x40 and 0x41).
The AUXIN1/AUXIN2 pins can also be used in con-
junction with the thermal supply pin (THRM) to monitor
external RTD devices. The THRM pin has an internal
switch connected to the internal-voltage regulator of the
MAX11068. The purpose of the switch is to save power
when a measurement of an external temperature-sens-
ing device is not needed. During normal operation, the
THRM pin is disabled. When the AIN1EN or AIN2EN bits
of the ADCCFG register (address 0x08) are enabled and
a measurement scan is initiated, a voltage source taken
from the internal regulator is connected to the THRM pin.
This occurs as soon as the scan signal is received and
before any cell or auxiliary channel measurements have
taken place. The THRM pin biases the RTD network so
that the effect of temperature on the RTD component
can be measured as a voltage by the ADC. Figure 25 is
the external temperature-sensor configuration.
Since the THRM pin is not driving the AIN pin application
circuit at all times, in some cases it may be necessary to
adjust the settling time seen by the AIN pins before the
measurement is started. A customized delay can be pro-
grammed through the ACQCFG register (address 0x0C)
AINCFG bits to allow the application circuit extra time to
settle before taking the ADC measurement for the AIN
pins. The AINCFG bits have a resolution of 5.3Fs, which
is also the minimum delay value. The maximum delay
is 339.2Fs. The programmed delay from the ACQCFG
register is implemented just before the measurement is
taken on an AIN channel. If both channels are enabled
for measurement, the delay is implemented twice, once
just before each channel’s measurement.
External Thermistor Supply Pin
Auxiliary Analog Inputs and