0
\$\begingroup\$

I am a student of Vehicle engineering. I had read a datasheet of a automotive failsafe IC:ATA6842 and I don't know what it is. Please have a look at P4 of the datasheet.

enter image description here

I know what in the red frame is a low side MOS BDC control circuit and a current differential amplification circuit.

But what I don't know is,what is the use of the circuit in the blue frame? What happene to the BDC motor with this circus?

enter image description here

\$\endgroup\$
3
  • 2
    \$\begingroup\$ A failsafe for what? The electric steering or the rear window wiper? What is the circuit supposed to do? Add information in the question rather than in the comments. I think you mean "circuit" - a circus is something else. \$\endgroup\$
    – Transistor
    Jul 27, 2016 at 16:07
  • \$\begingroup\$ "TCFET" stands for "Test Current FET", can be used to test if MR12 or MR34 and the current test circuitry work, without actually activating the motor. \$\endgroup\$
    – JimmyB
    Jul 27, 2016 at 18:47
  • \$\begingroup\$ @jimmyB Oh,it is what I don't know.Is this design really useful in reality?I think it will raise the cost. \$\endgroup\$
    – 梁政焘
    Jul 28, 2016 at 0:37

1 Answer 1

1
\$\begingroup\$

Your answer is on the block diagram on the preceding page of the datasheet:

enter image description here

The linked IC provides several low side drivers (which you've already identified in the red box) in addition to a high side gate driver for driving an external high-side n-ch MOSFET. The capacitors are connected to the pin labelled BSC (Bootstrap Capacitor) for the driver's integrated charge pump. TCFET (Test Current FET) drives the gate on MTCFET1 (and on MTCFET2, see below:)

enter image description here

Issuing a command to the IC that turns on TCFET drives current from the net labelled K15 (battery voltage after the ignition switch, via. DIN 72552) into the current measurement comparator inputs through an external shunt resistor which, as JimmyB points out in the comments, is helpful for testing the functionality of the low-side drivers and/or other external circuitry connected to TCFET without activating the motor. The output of the comparator could then be measured by an external A/D to verify proper functionality before an error condition occurs.

The relays RL1 and RL2 change the direction of the motor. Driving RL1 pulls the "top" of the motor to K30 (the battery voltage, again DIN 72552) and RL2 pulls the "bottom" to K30.

\$\endgroup\$
3
  • \$\begingroup\$ I know this.But what's the use of RL1 and MTCEFT1?Is this something for BDC motor driving? \$\endgroup\$
    – 梁政焘
    Jul 28, 2016 at 0:30
  • \$\begingroup\$ No, MCFET1 cannot "source current to the motor". Look at the circuit more closely. \$\endgroup\$
    – JimmyB
    Jul 28, 2016 at 11:50
  • \$\begingroup\$ You are absolutely correct, don't know how I missed it; thanks for pointing that out - edited the original answer. \$\endgroup\$ Jul 28, 2016 at 12:34

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.