L9300 datasheet(33/178 Pages) STMICROELECTRONICS

33 / 178 page

For all sensors, other than the standard active 2-level sensor, additional sensor data (diagnostics, etc.) are

decoded and available within the Remote Sensor Data Registers (WSIRSDR0, WSIRSDR1, WSIRSDR2, and

WSIRSDR3). Only for 2nd level PWM encoded sensors the user may choose to have all data processed through

the microcontroller by selecting pass through mode, WSIPTEN, within the Remote Sensor Configuration Register

(WSIRSCR). In pass-through mode, the remote sensor interface simply conditions the incoming sensor current

pulses to digital pulses, no decoding is performed. When STD sensor is selected, the IC automatically forces the

pass-through mode.

The sensor input filter time, deglitch filter, (delay until a threshold crossing is detected) can be configured in 15

steps. Filters can be selected individually for each channel, through the Remote Sensor Configuration Register,

WSFILT bits.

For PWM encoded sensors with two edges per tooth not in pass-through mode, the standstill signal can be

processed directly to the DOUTx output pins. This is done in the Remote Sensor Configuration Register, SSDIS

bit. Since the decoder has to measure the pulses in order to determine whether they are stand-still pulses or not,

the first standstill pulse will always be seen on the DOUTx output pins and the first not stand-still pulse after a

stand-still period will be suppressed.

Figure 17. Standstill operation when PWM two edges per tooth is selected

sensor

current

DOUT pin

Bit

SSDIS=0

DOUT pin

Bit SSDIS=1

Stand still

time

First not

standstill

pulse is

suppressed

GADG1307171232PS

Data from the sensor are not latched: last incoming frame overwrites the previous one once validated. Faults

coming from diagnostic (i.e. over current, short to ground or battery) are latched until the microcontroller reads

them.

Two different digital algorithms can be selected:

•

Auto-adjusting current trip points. With this option, the ASIC is able to find sensor DC current value (named

IB0) in the range from 2.5 mA to 21 mA (default is 7 mA). The ASIC is also able to detect the current value

of the data pulse and compute the first threshold (named Ith1): Ith1 = IB0 + ∆Ith1/2 where ∆Ith1 is in the

range from 5 mA to 9.3 mA (default is 7 mA).

Besides, in case of VDA selected, the ASIC is also able to recognize the current value of the speed pulse

by computing a second threshold (named Ith2): Ith2 = IB0 + ∆Ith1 + ∆Ith2/2 where ∆Ith2 in the range from

10 mA to 18.6 mA (default is 14 mA).

∆Ith1 can be read on WSIRSDR[4:7] and can assume values in the range form 54 to 100; ∆Ith2 can be

read on WSIRSDR[8:11] and can assume values in the range form 108 to 200. When one of delta is

saturated it is possible for the user to select whether this information should be flagged in WSIRSDR[0:3];

this can be done through Disable Delta Error bit on WSICTRL register.

•

Fixed current trip points where the thresholds are settled by SPI. To avoid the risk of wrong settings

(inverted thresholds, thresholds outside WSI limits and similar) only first threshold can be directly specified

while, to determine the second one, offset current information must be provided. Both values, threshold and

offset, can be specified through 8-bit word (range 0x00 → 0xFF): default values are 10 mA for first

threshold and 10 mA for offset (i.e. 20 mA default for second threshold). A fixed offset of 54 is added to SPI

value to prevent settings out of range. Complete formulas for threshold computation are the following

(ref_cur = ITH1/106):

–

First threshold = [ref_cur] * (54 + WSI_FIRST_TH )

–

Second threshold = [ref_cur] * (108 + WSI_FIRST_TH + WSI_OFFS_TH )

L9300

Power supply

DS12258 - Rev 5

page 33/178

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