4

4575D–BCD–09/05

ATA6830

3.

Functional Description

3.1

Analog Part

Figure 3-1.

Analog Blocks

The circuit contains an integrated 5V 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 oscilla-

tor 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 temperature 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