L9788 datasheet(136/264 Pages) STMICROELECTRONICS

136 / 264 page

Inductive sensor interface

L9788

136/264

DS12308 Rev 4

11.2

VRS - Normal mode

The VRS normal mode is set with VR_DIAG=0

In Normal mode, the circuit is configured as the one reported in Figure 56. It allows

decoding the VRS signal while flying wheel is in rotation.

Due to high variability of the input signal (±200 V) The input is clamped in the range

[VclpH:VclpL] in order to allow the analog circuitry processing the signal itself. Moreover, the

sensor input pins have an input common mode, VCM.

The preconditioned input signal is then processed by a zero-crossing comparator, which

toggles at each transition of the input signal.

Figure 56. VRS block diagram - Normal operating mode

To avoid spurious commutations of the zero crossing comparator, a hysteresis mechanism

is implemented. L9788 is able to sink a hysteresis current which generates a voltage drop

across the external resistors. The voltage levels related to the hysteresis function shown

hereafter are calculated considering an external series resistance of 10 kΩ on FLW_IN_P

and 10 kΩ on FLW_IN_N pins.

As reported in Figure 57, the Vdiff (FLW_IN_P - FLW_IN_N) input differential signal exhibits

some steps at each zero crossing:



when the output of the zero crossing comparator is high, the hysteresis current is kept

OFF;



when the output of the zero crossing comparator is low, the hysteresis current is

switched ON.

This approach applies the hysteresis current only on the transition L-H of the VRS_FB

signal.

FLW_IN_N

FLW_IN_P

VRS_HYST_FB

Filter Time

HYSTERESIS

SELECTOR

SENSOR

VRS

Vcm_NORM

LIMITED / FULLY

ADAPTIVE

MANUAL

SPI

VRS_CONF_

MODE_1

FLW_OUT

VRS_FB

GADG0612160922PS

L9788 Datasheet(PDF) 136 Page - STMicroelectronics

L9788 Datasheet(HTML) 136 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL