mc33991dwr2 Freescale Semiconductor, Inc, mc33991dwr2 Datasheet - Page 17

• Manufacturer Part Number: mc33991dwr2
• Description: Gauge Driver Integrated Circuit
• Manufacturer: Freescale Semiconductor, Inc

Table 12. RTZCR SI Register Assignment
combination is illustrated in Table 10. The default full step
time is 21.25 ms (0101). If there are two full steps per degree
of pointer movement, the pointer speed is: 1/(FS×2)°.
following a full step change, and before enabling the
integration of the non-driven coil signal. The blanking time is
either 512 µs, when D4 is logic [0], or 768 µs when D4 is logic
[1].
integrating the back EMF present in the non-driven coil during
the RTZ event. The integration circuitry is implemented using
a Sigma-Delta converter resulting in a representative value in
the 15-bit RTZ accumulator at the end of each full step. The
value in the RTZ accumulator represents the change in flux
and is compared to a threshold. Values above the threshold
indicate a pointer is moving. Values below the threshold
indicate a stalled pointer, thereby resulting in the cessation of
the RTZ event.
two’s complement. If the RTZR D3:D2 bits were written as 10
or 11, the ST14 bit corresponds to bit D14 of the RTZ
accumulator, the sign bit. After a full step of integration, a sign
into the RTZ integration accumulator to adjust the detection
threshold.
provided in Table 11.
Table 13. RTZCR Full Step Time
Analog Integrated Circuit Device Data
Freescale Semiconductor
Write
Bit D4 determines the provided blanking time immediately
Detecting pointer movement is accomplished by
The RTZ accumulator bits are signed and represented in
These bits are write-only.
RC12:RC5— These bits determine the preloaded value
Values range from -1 (00000000) to -4081 (11111111)
RC4—This bit determines the RTZ blanking time.
RC12
D12
RC3
0
0
0
0
0
0
0
0
1
1
1
1
RC11
D11
RC10
D10
RC2
0
0
0
0
1
1
1
1
0
0
0
0
RC9
D9
RC8
D8
Address: 101
RC7
D7
RC1
0
0
1
1
0
0
1
1
0
0
1
1
bit of 0 is the indicator of an accumulator exceeding the
decision threshold of 0, and the pointer is assumed to still be
moving. Similarly, if the sign bit is logic [1] after a full step of
integration, the accumulator value is negative and the pointer
is assumed to be stopped. The integrator and accumulator
are initialized after each full step.
preloaded accumulator for specific gauge, pointer, and full
step combinations. Bits D12:D5 are used to offset the initial
RTZ accumulator value, properly detecting a stalled motor.
The initial accumulator value at the start of a full step of
integration is negative. If the accumulator was correctly
preloaded, a free moving pointer will result in a positive value
at the end of the integration time. A stalled pointer results in
a negative value. The preloaded values associated with each
combination of bits D12:D5 are illustrated in Table 11. The
accumulator should be loaded with a negative value resulting
in a transition of the accumulator MSB to a logic [1] when the
motor is stalled. After a power-up, or any reset in the Default
mode, the 33991 device sets the accumulator value to -1,
resulting in an unconditional RTZ pointer movement.
• 0 = 512 µs
• 1 = 768 µs
an RTZ event, determining the pointer moving rate. Step
times range from 4.86 ms (0000) to 62.21ms (1111). Those
are illustrated in Table 10. The default time is 21.25 ms
(0101).
RC6
D6
Accurate pointer stall detection depends on a correctly
RC3:RC0— These bits determine the full step time during
RC5
D5
RC4
D4
RC0
TIMING DESCRIPTIONS AND DIAGRAMS
0
1
0
1
0
1
0
1
0
1
0
1
COMMUNICATION MEMORY MAPS
RC3
D3
RC2
D2
Full Step Time (ms)
RC1
13.06
17.15
21.25
25.34
29.44
33.54
37.63
41.73
45.82
4.86
4.86
8.96
D1
RC0
D0
33991
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