Data Sheet AS8446

Revision 1.8, Date 2005-03-17

Page 10 of 35

Programming Capabilities

There are in total 18 registers to program the behavior of the AS8446 via the Three Wire Interface

Register No

Register Name

Meaning

R1<4:0>

SRon

EMC parameter 1, rising edge

R2<4:0>

SRon_stat

EMC parameter 2, rising edge

R3<2:0>

SRon_min

EMC parameter 3, rising edge

R4<4:0>

SRoff

EMC parameter 1, falling edge

R5<3:0>

Sroff_stat

EMC parameter 2, falling edge

R6<1:0>

Acu_on/off

EMC parameter, rising and falling edge, multiplying factor 1 or 2

R7<4:0>

AV_TRIMM

Motor current measurement amplification (steps of 1.25%)

R8<1:0>

AV_RANG_norm

Motor current measurement amplification, normal measurement channel (large

steps)

R9<2:0>

OVERC_level

Over current threshold value

R10<1:0>

AV_RANG_over

Motor current measurement amplification, over current measurement channel

(large steps)

R11<2:0>

VBAT_RANG

Range of supply voltage (max. battery voltage to measure)

R12<2:0>

OVER_VOLT

Over voltage threshold value

R13<2:0>

UNDER_VOLT

Under voltage threshold value

R14<0:0>

VPUMP_MIN

Min. pumped voltage (Vpump – Vbat)

R15<3:0>

ADC_CH

Selection of one of the analog channel to be connected to pin ADC (Analog-

MUX)

R16<0:0>

WATCH_D

Switch on or off of watch dog function

R17<1:0>

SLEEP

Switch on or off of sleep mode

R18<7:0>

FAILURE_STAT

Failure status register

Full descriptions of all registers see below.

Table 10

Meaning of the AS 8446 registers.

Driver Programming (Slew Rate Regulation Parameters)

The Power FET driver is controlled in two different ways:

1. By the digital input PWM (output of the PWM generator of the

µP) to realize the PWM duty cycle of the motor drive for

regulating the motor current, speed or voltage in the closed loop.

2. By the dynamically self-adjusting slew rate regulated switching technology during the rising and falling edges of the

motor voltage.

There are 6 registers to program the driving parameters in different time intervals of the rising and the falling edge of the motor

voltage independently (definition of the time functions of the power FET driver gate currents in wide ranges):

Rising edge: registers R1<4:0>, R2<4:0>, R3<2:0> and R6<0>

Falling edge: registers R4<4:0>, R5<3:0> and R6<1>

These registers can be programmed via the Three-Wire Interface and thus the EMC behavior of the system (motor, power

switches, cables) can be adapted and optimized to a particular application. Although the total rising and falling times are very

See also section Summary of all programmable registers (parameters, functions).

A detailed description of these programming and EMC optimization will be given in the application manual of the AS8446.