50V 3-Phase BLDC Motor Driver Circuit

This yet another versatile 3-phase driver device in the form of IC L6235  from ST Microelectronics allows you to drive a 50V 3-phase BLDC motor with extreme efficiency.The chip also includes all the required protection features built-in, along with an easy to configure external speed control stage.

How the IC L6235 BLDC Driver Works

The IC L6235 is an embedded DMOS 3-phase motor driver with an integrated over-current protection. Designed with BCD technology, the device embeds the benefits of isolated DMOS power transistors with CMOS, and with bipolar circuits within the same device.

The chips integrates all the circuitry required for effectively driving a 3-phase BLDC motor, as explained below:

A 3-phase DMOS bridge, a constant off-time PWM current controller and the decoding logic for single ended hall sensors for generating the essential 120 degree phase shift sequence for the power stage.

With regard to the built-in protections the L6235 device offers a non-dissipative over current protection on the high-side power MOSFETs, protection against ESD, and an automatic thermal shutdown in case the device heats up above the rated value.

50V BLDC Driver Circuit Schematic

A typical L6235 50V 3-phase BLDC motor driver circuit application can be witnessed above, which looks quite straightforward with its implementation procedures.

You just have to hook up the shown elements in place and use the design to operate any BLDC motor with sensors rated within 8V to 50V at 3 amps rate.

Pinout Details

The pinout function for the specified circuit can be studied from the following data:

Pin#6, 7, 18, 19 = (GND) These are the Ground terminals of the IC.

Pin#8 = (TACHO) It's designated as the open drain output Frequency-to-voltage open drain output. here each single pulse from pin H1 is dimensioned in the form of a fixed and adjustable length pulse.

Pin#9 = (RCPULSE) Is configured like a parallel RC network attached between this pin and the ground, which fixes the period of the monostable pulse responsible for the frequency-to-voltage converter.

Pin#10 = (SENSEB) This pin must be connected together with pin SENSEA to power ground through a sensing power resistor. Here the inverting input of the sense comparator also needs to be connected.

Pin#11 = (FWD/REV) This pinout can be used for changing the rotational direction of the BLDC motor. A HIGH logic level on this pinout will cause a forward motion while, a LOW logic level will allow the BLDc motor to rotate in the opposite reverse direction. For enabling a fixed clockwise or anticlockwise directions, this pinout may be appropriately terminated to a +5V or the ground line..

Pin#12 = (EN) A LOW logic signal will shut OFF all the internal power MOSFETs and stall the BLDC motor. In case this pinout is intended to be not used, it must be terminated to the +5 V supply rail.

Pin#13 = (VREF). You can see an opamp configured with this pinout. The Vref input of the opamp connected with this pinout can be fed with a linearly adjustable 0 to 7V for changing the speed of the BLDC motor from 0 to max. If not used make sure to connect this pinout to GND.

Pin#14 = (BRAKE) A LOW logic level on this pinout will switch ON all highside Power MOSFETs, instantly enforcing the brake/stop function. In case not used, this pinout can be held connected to +5 V.

Pin#15 = (VBOOT) It is simply the input pinout for the bootstrap voltage needed for driving the upper Power MOSFETs. Just connect the parts as indicated

Pin#5, 21, 16 = (3-phase OUT to BLDC motor) Power output which connects with the BLDC motor and powers the motor.

Pin#17 = (VSB) Just connect it as shown in the diagram. Pin#20 = (VSA) Same as above, needs to eb connected as given in the diagram.

Pin#22 = (VCP) It is the output from the internal charge pump oscillator, connect the parts as shown in the diagram.

Pin#1, 23, 24 = 3-Phase sequential signal from the BLDC single ended Hall sensor can be configured with these pinouts, if the BLDC is a sensorless, you can feed an external 3-phase 120 degree apar input on these pinout at +5V level.

Parts List for the above discussed 50V 3-phase BLDC motor driver circuit

C1 = 100 µF
C2 = 100 nF
C3 = 220 nF
CBOOT = 220 nF
COFF = 1 nF
CPUL = 10 nF
CREF1 = 33 nF
CREF2 = 100 nF
CEN = 5.6 nF
CP = 10 nF
D1 = 1N4148
D2 = 1N4148
R1 = 5.6 K
R2 = 1.8 K
R3 = 4.7 K
R4 = 1 M
RDD = 1 K
REN = 100 K
RP = 100
RSENSE = 0.3
ROFF = 33 K
RPUL 47 K
RH1, RH2, RH3 = 10 K

For more details you can refer to the following datasheet from ST: DMOS driver for 3-phase BLDC motor