ATA6834 ATMEL Corporation, ATA6834 Datasheet - Page 11

• Manufacturer Part Number: ATA6834
• Description: (ATA6833 / ATA6834) BLDC Motor Driver and LIN System Basis Chip
• Manufacturer: ATMEL Corporation

3.8
3.9
9122D–AUTO–09/09
Short Circuit Detection
Cross Conduction Timer
Short circuits in the motor bridge circuitry are sensed by S1 to S3 inputs. Internal comparators
monitor the voltage differences between the drain and the source terminals of the external
power-NMOS transistors. If one transistor switches on and its drain-source voltage exceeds V
threshold (typically 4V) after a blanking time t
this branch will be detected. In this case, all output drivers will be switched off immediately and
pin DG1 will be set to HIGH. With a rising edge at any of the pins IL1 to IL3 or IH1 to IH3, the
diagnostic output DG1will be reset and the drivers can be switched on again.
In order to prevent damage of the motor bridge due to peak currents a non-overlapping phase
for switching the power-NMOS transistors is mandatory. Therefore, a cross conduction timer has
been implemented to prevent switching on any output driver for a time t
has been switched off. This also accounts for toggling any other driver after a short circuit was
detected. An external RC parallel combination defines the value for t
follows:
page
The RC combination is connected between CC and GND pins. When one of the drivers has
been switched off the RC combination is charged to 5V (VINT) and discharged with its time con-
stant. Any low to high transition at the control inputs will be masked out at the driver outputs until
the voltage at CC pin drops below 67% of its initial value (VINT). The timer will be re-triggered at
any time by any falling edge at the control inputs. This is shown in the following figure.
Figure 3-6.
At least 5 k minimum and 5 nF at maximum should be used as values for the RC combination.
10 k is recommended. If the non-overlapping phase is controlled by the external microcon-
troller, it is possible to do without the external capacitor. The minimum time t
parasitic capacitance at CC pin.
t
CC
= K
16.
CC
IH1
IL1
IL3
CC
H1
R
L1
L3
Interaction of Short Circuit Detection and Cross Conduction Timer
CC
V
V
[k ]
CC
CC
if V
= V
= 67% V
PBAT
Shut off
VINT
- V
C
S1
CC
VINT
> 4V
[nF], K
ATA6833/ATA6834 [Preliminary]
t
cc
CC
is specified in
for t
for t
Ignore V
Ignore V
SC
SC
= 6 µs
= 6 µs
SC
S1
S3
(typically 6 µs, see
if V
if V
Shut off
Shut off
S1
S3
Section 8. “Electrical Characteristics” on
> 4V
> 4V
t
cc
t
cc
Figure
CC
www.DataSheet4U.com
and can be estimated as
CC
Ignore V
for t
3-6), a short circuit in
after any other driver
SC
CC
PBAT
= 6 µs
is defined by the
- V
S1
11
SC