MAX11068EVKIT+ Maxim Integrated Products, MAX11068EVKIT+ Datasheet - Page 32

• 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 MAX11068 incorporates the capability to check
the health of its internal voltage reference and regula-
tor output. The results are stored in the DIAG register.
Conversions are enabled by setting the DIAGEN bit of
the ADCCFG register (address 0x08). They are initiated
immediately following the cell conversions. For the self-
diagnostic measurement, the ADC reference is taken
from the internal THRM pin connection. This makes
the full-scale range of the self-diagnostic measurement
3.4V. The reference voltage is measured differentially
against the internal voltage on C0 through an instrumen-
tation amp, the low-voltage mux, and finally the internal
ADC. The instrumentation amp has a gain of 1/2 that
must be taken into account when calculating the expect-
ed diagnostic result. The complete block diagram for the
self-diagnostic measurement is shown in Figure 26.
The expected value of the self-diagnostic measurement
varies depending on the regulator output voltage, the
reference voltage itself, and the accuracy of the ADC.
When discussing the DIAG measurement values, the
least significant nibble of the DIAG register is ignored
since only the three most significant nibbles contain
real data. To first order, the expected value of the self-
diagnostic measurement is:
Since the specified regulator voltage can vary by
approximately Q10%, the expected result of the self-
diagnostic varies proportionally. For typical values of
REF = 2.5V and VAA = 3.4V, the nominal DIAG value for
normal operation is 5E1h with a tolerance of Q150 LSBs
(Q0x96). Typical devices may vary from this value due
to trim differences. Table 3 shows typical values and
Table
32
REF pin is open or floating
REF is shorted to AGND
FAULT CONDITION
3. DIAG Typical Values and Ranges
DIAG
C0 is open
None
=
(
(
REF C0
−
)
×
0.5 VAA
DIAG VALUE (TYPICAL)
Self-Diagnostics
0x1DA to 0x1DC
0x3C1 to 0x7AE
0x292 to 0x293
)
0x5E1
×
4096
Use ALRTREF in the FMEA register
DIAG VALUE RANGE (TYPICAL)
Figure 26. Block Diagram of Self-Diagnostic Mode
Connections
ranges for the DIAG value for various fault and no-fault
conditions.
In a typical application, the self-diagnostic measurement
should be performed and stored when the system is
operated for the first time. By periodically performing a
new measurement, the results can be compared against
the original value to verify that the system is operating
at the expected performance level. As shown in Table
2, a change on the order of P 4 LSBs can be expected
across the full temperature range.
The REF pin also has a special failure-mode effects
analysis (FMEA) detector to alert when an open-circuit
may exist. The alert is the ALRTREF bit of the FMEA
register. It detects when the REF pin has an oscillating
voltage condition, which is a symptom of an open circuit
on the pin.
0x1DA to 0x1DC
0x54B to 0x677
0x292 to 0x293
DIAGNOSTIC
G = 1/2
INSTR
AMP
SELF -
REF
C0
MUX
VARIATION FROM INITIAL
LV
VALUE (LSB)
ADC IN +
ADC IN -
+4 to -4
THRM
—
—
—
12-BIT ADC