TCA 3727G Infineon Technologies, TCA 3727G Datasheet - Page 20

• Manufacturer Part Number: TCA 3727G
• Manufacturer: Infineon Technologies

Specifications of TCA 3727G

• Packages: PG-DSO-24
• Ipeak: 2 x 1.0 A
• Inhibit: Y
• Iq (typ): 20.0 µA
• Mounting: SMT
• Technology: Bipolar

TCA3727G
Application Hints
The TCA3727G is intended to drive both phases of a stepper motor. Special care has been taken to provide high
efficiency, robustness and to minimize external components.
Power Supply
V
The TCA3727G will work with supply voltages ranging from 5 V to 50 V at pin
. As the circuit operates with
S
chopper regulation of the current, interference generation problems can arise in some applications. Therefore the
power supply should be decoupled by a 0.22 F ceramic capacitor located near the package. Unstabilized
supplies may even afford higher capacities.
Current Sensing
R
R
The current in the windings of the stepper motor is sensed by the voltage drop across
and
. Depending on
1
2
the selected current internal comparators will turn off the sink transistor as soon as the voltage drop reaches
R
R
certain thresholds (typical 0 V, 0.25 V, 0.5 V and 0.75 V); (
,
= 1 ). These thresholds are neither affected by
1
2
V
V
variations of
nor by variations of
.
L
S
R
R
Due to chopper control fast current rises (up to 10 A/ s) will occur at the sensing resistors
and
. To prevent
1
2
R
R
malfunction of the current sensing mechanism
and
should be pure ohmic. The resistors should be wired to
1
2
GND as directly as possible. Capacitive loads such as long cables (with high wire to wire capacity) to the motor
should be avoided for the same reason.
Synchronizing Several Choppers
In some applications synchronous chopping of several stepper motor drivers may be desirable to reduce acoustic
interference. This can be done by forcing the oscillator of the TCA3727G by a pulse generator overdriving the
oscillator loading currents (approximately
100 A). In these applications low level should be between 0 V and
V
1 V while high level should be between 2.6 V and
.
L
Optimizing Noise Immunity
Unused inputs should always be wired to proper voltage levels in order to obtain highest possible noise immunity.
To prevent crossconduction of the output stages the TCA3727G uses a special break before make timing of the
power transistors. This timing circuit can be triggered by short glitches (some hundred nanoseconds) at the Phase
inputs causing the output stage to become high resistive during some microseconds. This will lead to a fast current
decay during that time. To achieve maximum current accuracy such glitches at the Phase inputs should be
avoided by proper control signals.
Thermal Shut Down
To protect the circuit against thermal destruction, thermal shut down has been implemented. To provide a warning
in critical applications, the current of the sensing element is wired to input Inhibit. Before thermal shut down occurs
Inhibit will start to pull down by some hundred microamperes. This current can be sensed to build a temperature
prealarm.
Data Sheet
22
Rev. 2.2, 2009-01-22