4

ATA6830

4575C–BCD–05/03

Functional Description

Analog Part

Figure 3. Analog Blocks

The circuit contains an integrated 5 V regulator to supply the internal logic and analog

circuit blocks. The regulator uses an adjusted bandgap as voltage reference. Also all

other parts that require an excellent voltage reference, such as the voltage monitoring

block refer to the bandgap.

The bias generator derives its accurate currents from an external reference resistor. The

oscillator is used for clocking the digital system. All timings like the baud rate, the step

duration and the chopper frequency are determined from it. An external capacitor is

used for generating the frequency.

The voltage monitoring enables the circuit to drive the stepping motor at different battery

voltage levels. According to the battery voltage the stepping motor will be accelerated to

a maximum step velocity. In case of under or over voltage the motor will shut off. A tem-

perature monitoring is used for shut off at overtemperature conditions and current boost

in case of low temperature.

Oscillator

Bias

Generator

Bandgap

Voltage

Regulator

Voltage

Supervisor

COS

RSET

AGND

VSS

VDD

VBAT

Temperature

Supervisor

Bias

Clock

Supply

Reset

Voltage Levels

Temperature Levels