Intersil HIP4086, HIP4086DEMO1Z User Manual

Application Note 1829

Author: Richard Garcia

HIP4086 3-phase BLDC Motor Drive Demonstration
Board, User’s Guide

Introduction

The HIP4086DEMO1Z is a general purpose 3-phase BLDC
motor drive with a microprocessor based controller. Hall effect
shaft position sensors are used to control the switching
sequence of the three 1/2 bridge outputs. The bridge voltage
can vary between 12V and 60V and the maximum summed
bridge current is 20A (with sufficient air flow). This motor drive
can be used as a design reference for multiple applications
including e-bikes, battery powered tools, electric power
steering, wheel chairs, or any other application, where a BLDC
motor is utilized. Because this demonstration board is
primarily intended to highlight the application of the HIP4086
3-phase MOSFET driver with no specific application targeted,
the control features are limited to simple functions, such as
start/stop, reverse rotation, and braking. Open loop speed
control is implemented. More advanced control features, such
as torque control, speed regulation and regenerative braking
are not implemented because these methods require close
integration with the characteristics of the load dynamics.

Important Note

Because Hall sensor switching logic sequences for BLDC
motors are not all the same, this demo board supports most, if
not all, variations of sequence logic. Please refer to the
sequence charts in “Selecting the Correct Switching
Sequence” on page 9 to verify that your desired sequence is
implemented. If you require a different sequence for your
specific motor application or if you need help identifying the
correct switching sequence for your specific motor, please
contact Intersil prior to ordering this demo board for possible
support for a new switching sequence.

analog signal proportional to the motor current is available on
board as a design reference.

The microcontroller firmware is also provided as a reference
but the only support offered by Intersil will be for bug
corrections and for adding more switching sequences. Please
refer to Microchip for details on the use of the PIC18F2431.

Physical Layout

The HIP4086DEMO1Z board is 102mm by 81mm. The tallest
component is a 470µF capacitor. The total height is 24mm
with standoffs or 18.5mm without standoffs. The Hall effect
shaft position sensor inputs are miniature terminal blocks and
the high current outputs are larger terminal blocks that are
rated for 20A.

Four push-buttons are used for reset, brake, reverse, and
start/stop functions. An on-board potentiometer is used to
adjust the duty cycle of the applied motor voltage or an
optional external potentiometer can be connected to a signal
terminal block located adjacent to the Hall terminal blocks.

The switching sequence selection dip switch is used for various
purposes but the most important function is to select the
desired switching sequence. Please refer to the “Setup and
Operating Instructions” on page 3 for more information.

For those customers who would like to modify the firmware of
the PIC18F2431 microcontroller, an RJ25 connector is
provided for easy connection with Microchip firmware
development tools (not provided or supported by Intersil).

Specifications

Motor topology 3-phase BLDC motor with Hall

sensors

Operating voltage range 15VDC to 60VDC

Maximum bridge current 20A (with sufficient air flow)

Hall sensor bias voltage 5V

PWM switching frequency 20kHz

Scope

This application note covers the design details of the
HIP4086DEMO1Z with a focus on the design implementation
of the HIP4086 driver using recommended support circuits.

Also covered, is the design method of the bipolar current
sensing feature. Presently, current sensing on this demo board
is used only for pulse-by-pulse current limiting. However, an

March 14, 2013
AN1829.0

1

FIGURE 1. HIP4086DEMO1Z INPUTS AND OUTPUTS

CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.

1-888-INTERSIL or 1-888-468-3774

Intersil (and design) is a trademark owned by Intersil Corporation or one of its subsidiaries.

All other trademarks mentioned are the property of their respective owners.

|Copyright Intersil Americas LLC 2013. All Rights Reserved

Block Diagram

FIGURE 2. HIP4086DEMO1Z BLOCK DIAGRAM

HIP4086DEMO1Z

ISL8560

+5V

BUCK

REGULATOR

HIP4086
3-PHASE
MOSFET

DRIVER

ISL6719

LINEAR +12V

REGULATOR

CONTROLLER

LEDS

DIP

SWITCHES

PUSH

BUTTONS

15V TO 60V

3-PHASE

BRIDGE

BLDC

MOTOR

ISL28246

CURRENT

LIMIT

AND

MONITOR

HALL

INPUTS

4

3

6

6

2

3

Application Note 1829

The HIP4086DEMO1Z is composed of six major circuits
illustrating the use of several Intersil products.

Bias Supplies

The ISL8560 is a buck regulator with integrated power FETs that
provides +5V bias for the microcontroller, dip switches, push
buttons, LEDs, and the current monitor/limit circuits. The
ISL6719 is a linear regulator that provides 12V bias for the
HIP4086 3-phase MOSFET driver. Please refer to the ISL8560

datasheet for application information.

datasheet or the ISL6719

HIP4086

The HIP4086, the featured Intersil part, drives 3 bridge pairs of
F540NS power FETS with a PWM frequency of 20KHz. Associated
with the HIP4086 are the necessary support circuits such as the
boot capacitors and boot diodes. Recommended negative
voltage clamping diodes on the xHS pins are also provided.

MicroController

The Hall sensor inputs are decoded by the microcontroller to
provide the appropriate switching sequence signals to the
HIP4086 to drive the six F540NS bridge FETs that are connected
to a 3-phase BLDC motor. In addition to decoding the Hall
sensors, the microcontroller also multiplexes the dip switches
(for switching sequence options), the push buttons (for various
control functions of the motor), and the LED status lights.

The on-board potentiometer (or an optional external pot) is
monitored by the microcontroller to provide a duty cycle to the
motor that is proportional to the tap voltage of the potentiometer

2

and varies between 0% and 100% duty cycle. This proportional
duty cycle is open loop and is independent of the bridge voltage.
Consequently, any motor voltage between 15V and 60V can be
used with this demo board.

The microcontroller firmware is provided as a reference but the
only support offered by Intersil will be for bug corrections and for
adding more switching sequences. All firmware revisions for this
demo board can be found on the Intersil website. The firmware
revision of your demo board can be determined by referring to
the “Test Mode Setup” on page 24.

Current Sensing/Current Limit

Two ISL28246 low offset, dual op-amps are used for current
monitoring and current limiting. One op-amp is configured as a
differential amplifier for Kelvin connections across the current
sensing resistor. The diff-amp is also biased so that zero bridge
current results with an output voltage that is 1/2 of the +5V bias.
Consequently, positive bridge currents results with a current
monitor signal that is greater than 2.5V (up to ~5V). Negative
bridge currents (that occur with regenerative braking) is less than

2.5V (down to a minimum of ~0V). This ‘”bipolar” analog signal
can be monitored by the microcontroller for purposes, such as
torque control and/or regenerative braking.

The output of the analog differential amplifier is also connected
to two op amps configured as outside window comparators for
pulse-by-pulse current limits for either positive or negative bridge
currents. The OR’ed comparator outputs are sent to the
microcontroller for processing.

AN1829.0

March 14, 2013

Application Note 1829

ISL6719

(+12v)

FIGURE 3. MAJOR CIRCUIT LOCATIONS

3-phase Bridge

The 3-phase bridge is composed of six F540NS power MOSFETS
(100V, 33A). Each FET is driven by one of the six driver outputs of
the HIP4086. Dead time is provided by the controller (optionally,
dead time can be provided by the HIP4086).

Related Literature

• FN4220 HIP4086, 80V, 500mA, 3-Phase MOSFET Driver

• FN6555

• FN9244

• FN6321
Input-Output (RRIO) Op Amps

ISL6719, 100V Linear Bias Supply

ISL8560, DC/DC Power Switching Regulator

ISL28246, 5MHz, Single and Dual Rail-to-Rail

Setup and Operating Instructions

Required and Recommended Lab Equipment

Lab supply (or battery), 15V minimum to 60V absolute
maximum. The current rating of the lab supply must have
sufficient capacity for the motor being tested. If a battery is the
power source, it is highly recommended that an appropriate fuse
be used listed as follows:

•Bench fan

•Test motor

• Multichannel oscilloscope, 100 MHz

•Multimeter

• Temperature probe (optional)

CAUTION: If the HIP4086DEMO1Z is used for an extended period
at high power levels, it may be necessary that a fan be used to
keep the temperature of the bridge FETs to less than +85°C (as
measured on the heat sink plane).

1. Connect the 3-phase motor leads to the MA, MB, and MC
terminal blocks. For high current applications, it is
recommended that both terminals of each block be used. It is

3

also recommended that during initial setup the motor
mechanically loaded.

2. Connect the HALL sensor leads of the motor to the HA, HB,
and HC terminals. The +5V bias and ground leads must all be
connected.

3. Rotate the R13 potentiometer to the left (CCW) until it clicks.
This will set the starting voltage on the motor to a minimum.

4. Setup the dip switch for the correct switching sequence (see
the switching sequence tables at the end of this application
note).

5. With a lab supply turned off but previously set to the desired
bridge voltage, connect the lab supply (or battery) to the
+BATT a nd -B ATT terminal bloc k .

6. Ensure that the motor is securely mounted prior to proceeding
with the following steps. Also, do not exceed the maximum
rated RPM of your motor.

7. Turn on the lab supply. Observe that the four LEDS turn on and
off, one after another. This initial flash of the LEDs indicates
that power has been applied. After the initial flash, all LEDs
will be off. Operation of the motor is now possible. Note that
the dip switch options are read at initial turn-on and changing
the settings after power is applied will have no effect. As an

not be

AN1829.0

March 14, 2013

Application Note 1829

led0led2led3 led1

At initial turn on , leds will turn on and

off one at a time sta rtin g with le d0

led0led2led3 led1

While the motor is rotating, the RUN LED is blinking

RUNREVERSEBRAKE

ILIMIT

led0led2led3 led1

RUNREVERSEBRAKEILIMIT

led0led2led3 led1

RUNREVERSEBRAKE

ILIMIT

led0led2led3 led1

RUNREVERSEBRAKE

ILIMIT

blinking

led0led2led3 led1

RUNREVERSEBRAKE

ILIMIT

led0led2 led1

RUNREVERSEBRAKE

ILIMIT

led3

alternative to cycling power, the reset push button can be
pressed to re-read the dip switch settings.

8. Press the Start/Stop push button once. The RUN LED (led0)
will blink, indicating that the motor has been started. The
motor at this point may not be rotating because minimal
voltage is being applied to the motor.

9. Slowly increase the voltage on the motor by rotating the
potentiometer, R13, to the right (CW). At some point the
motor will start to rotate slowly. The actual starting voltage is
dependent on the specific motor being used.

10. If the motor is vibrating back and forth instead of rotating, it
is possible that the Hall sensors or the motor leads were not
connected correctly. If the correct switching sequence has
been selected, all that should be necessary to correct this
misbehavior is to swap two of the motors lead (or to swap two
of the Hall sensor leads).

11. Continue to rotate the pot until the motor is running at a
moderate speed of roughly 25%. Do not run the motor with
maximum voltage until the setup check-out is completed.

12. Press again the START/STOP push button. The motor will free
wheel to a stop and the blinking led0 will turn off.

13. Press again the START/STOP button. The motor will
accelerate to the previous run speed (assuming that the
potentiometer was not rotated). The blinking led0 will also
turn on.

14. While the motor is running, press the REVERSE button. The
RUN LED (led0) will turn off and the REVERSE LED (led1) will
turn on without blinking. After a short pause while the motor
is freewheeling to a stop, the motor will restart rotating in the
opposite direction. The RUN LED will be blinking and the
REVERSE LED will continue to be on.

15. Press again the REVERSE button. As before, the motor will
stop. But this time the REVERSE LED will turn off. After a
pause, the motor will restart but this time rotating in the
forward direction.

16. While the motor is running, the motor can be hard braked by
pressing the BRAKE push button. The BRAKE LED (LED2) will
be on without blinking. When the motor is restarted, the
BRAKE LED will turn off.

CAUTION: The braking method implemented turns on all of the
low-side bridge FETs simultaneously. This will force the motor to
a very rapid stop. If the motor is loaded, or if the motor is not
designed for a rapid stop, mechanical damage to the motor or
the load can result. If you are not sure about using this braking
method, only apply the brake when the motor speed is relatively
slow.

17. If while operating, the motors turns off, and the iLIMIT LED
(led3) is blinking, the current limit shut-down has been
activated after 255 consecutive pulse-by-pulse current limits.
This may happen if the motor speed is accelerated too
quickly, or if there is a fault with the motor or connections, or
if the motor is stalled.

4

It is now safe to proceed with testing at higher power levels
speeds.

AN1829.0

March 14, 2013

Application Note 1829

BLDC

MOTOR

AHO

ALO BHO

BLO

CHO

CLO

000 100 110 111 011 000 100 110 111 011001 001

HALL SENSOR LOGIC

HC

HB

HA

ZLP PLZ PZL ZPL LPZ LZP ZLP PLZ PZL ZPL LPZ LZP

MB

MA

MC

1 2 3 4 5 6 1 2 3 4 5 6

0° 60° 120° 180° 240°

Bridge State Logic: P = PWM, L = Low, Z = off

0° 60° 120° 180° 240° 0°

SEQUENCE STEP NUMBERS

Z

L

P

ZLP PLZ PZL ZPL LPZ LZP ZLP PLZ PZL ZPL LPZ LZP

MB

MA

MC

Bridge State Logic: P = PWM, L = Low, Z = off

IDEALIZED MOTOR VOLTAGE WAVEFORMS

MC

MB

MA

+Vbat

-Vbat

~ ½ Vbat

20kHz PWM freq.

Motor rotation period

per pole

Theory of Operation

The HIP4086DEMO1Z demonstration board is a general purpose
3-phase BLDC motor controller. Three half bridge power circuits
drive the motor as shown in Figure 4.

Three 6 step bridge state logic diagrams, illustrated in Figure 5,
are used to drive the motor. The bridge state logic diagrams
represents the logic status of the each half bridge but the actual
voltage applied to the motor appears much differently. Figure 6
illustrates the bridge status logic vs the actual voltage waveforms
applied to each motor lead.

The HIP4086 has 6 driver outputs, AHO, ALO, BHO, BLO, CHO,
and CLO, to control the six bridge FETs individually. If the gate
drives for both FETs of one half bridge are low, current will not
flow in the corresponding motor lead (high impedance or Hi-Z). If
the gate drive for the low FET is high and the gate drive for the
high FET is low, then the phase node of that half bridge, and the
corresponding motor lead, is connected to ground (Low). If the
low and high gate drives are complementary driven, the phase
node can be pulse width modulated (PWM) to control the
average voltage on that motor lead.

The motor rotation period and the amplitude of the bridge
voltage waveforms are modified by the microcontroller to control
the speed of the motor. Pulse width modulation is used to modify
the amplitude of the voltage waveforms and the motor rotation
period is established by the shaft position hall sensors that signal
the controller to change the switching sequence. Typical hall
sensor logic is illustrated in Figure 5. Each hall logic diagram, HA,
HB, and HC, correspond respectively to the bridge state logic
diagrams, MA, MB, and MC. For example, the transition of the
hall sensor logic, from step 1 to 2, results with the drive
waveform transition of ZLP to PLZ where P, L, and Z define the
state of each half bridge.

FIGURE 5. HALL SENSOR LOGIC vs BRIDGE STATE LOGIC

FIGURE 4. BASIC BLDC MOTOR POWER TOPOLOGY

5

FIGURE 6. BRIDGE STATE LOGIC vs MOTOR VOLTAGE

March 14, 2013

AN1829.0

Application Note 1829

FIGURE 7. SEQUENCE STEPS 1 TO 3

N

N

S

S

N

S

N

S

N

S

N

S

N

S

N

S

S

S

N

N

2

P

Z

L

3

P

L

Z

N

S

N

S

N

S

N

S

N

S

N

S

N

S

N

S

HC
HB
HA

MB

MA

MC

1

2 3

HC
HB
HA

MB

MA

MC

HC
HB
HA

MB

MA

MC

L

L

L

P

P

P

Z

Z

Z

Z

ZPP L

L

1

Z L

NEUTRAL

P

Z

P

L

NEUTRAL NEUTRAL

NEUTRALNEUTRALNEUTRAL

NEUTRAL

NEUTRAL NEUTRAL

NEUTRAL NEUTRAL NEUTRAL

FIGURE 8. SEQUENCE STEPS 4 TO 6

S

N

S

N

S

N

S

N

S

N

S

N

4

Z

L

P

5

L

Z

P

6

L

P

Z

S

S

N

N

N

N

S

S

S

N

S

N

N

S

N

S

N

S

N

S

N

S

N

S

64 5

HC
HB
HA

MB

MA

MC

HC
HB
HA

MB

MA

MC

HC
HB
HA

MB

MA

MC

L Z

P

LL

PP Z

Z

Z

Z

Z

P

PP

L

L

L

NEUTRAL NEUTRAL NEUTRAL

NEUTRALNEUTRALNEUTRAL

NEUTRAL NEUTRAL NEUTRAL

NEUTRAL NEUTRAL

NEUTRAL

Switching Sequence Phase Currents

The following motor winding diagrams illustrate how currents
flow in a 3-phase BLDC motor during each switching period of the
6 step voltage waveform. These diagrams are for a very simple
motor with only 6 stator poles. Most 3-phase motors have more
stator poles (multiples of 6) to reduce torque modulation
(cogging) but the principles of operation are the same.

Each phase winding is color coded and black arrows indicate the
direction of positive current in that winding for each step. As
described in Figure 7, the half bridge state of each motor lead,
MA, MB, or MC, is labeled with P, L, or Z. Observe that the active

coils are highlighted. The inactive coils (those with no current) are
white.

The dark gray structures are the permanent magnets that are
mounted on the light gray rotor. The bold black arrow is the flux
vector of the permanent magnets. The bold dark blue arrow is
the magnetic flux vector generated by the active coils for each
waveform step. The switching step occurs when these two
vectors are perpendicular for maximum torque. Notice how the
flux vectors are rotating counter clockwise, 60° for each step.

This tutorial for BLDC motors is very fundamental. For more
information about a specific motor, please contact the motor
manufacturer.

6

AN1829.0

March 14, 2013

Application Note 1829

AHO

CLO

BLO

ALO

CHO

BHO

CLI

BLI

ALI

CHI

BHI

AHI

CHS

AHS

BHS

CHB

AHB

BHB

VDD

RDEL

HIP4086/A

VSS

MOTOR

VDD V

BAT

CURRENT

SENSE

RFSH

D1

R1

Q1

Q2

C1

C2

VSS

xHS

xLO

xHO

INDUCTIVE

MOTOR LOAD

+

-

+

-

DEAD-TIME

PHASE NODE

(xHS)

LO GATE DRIVE

HI GATE DRIVE

LO FET CURRENT

HI FET CURRENT

di/dt

~-1.5V

0V

NEG. TRANSIENT

(-Ldi/dt)

HIP4086 Circuit Description

In the following discussion, xHI, xLI, xHO, xLO, and xHS is a short
hand notation where the x can be replaced with A, B, or C. An “x”
pin implies that the reference is applicable to the corresponding
A, B, or C pins of the driver.

The simplified schematic of Figure 9 illustrates the three power
stages of the motor driver. Each phase is identical in component
selection. For specific component values and complete circuit
details, please refer to the Bill of Materials (BOM) on page 12
and PCB Layout schematics beginning on page 18.

FIGURE 9. SIMPLIFIED 3-PHASE BRIDGE

Series connected gate resistors on each bridge FET are used to
reduce the switching speed to help minimize EMI radiating from
the power leads to the motor. The user can change these values
if desired, keeping in mind that if the gate resistors are made
larger, the turn off delays of the FETs will also increase, which
may require additional dead time.

All of the xHS pins have recommended external snubber circuits
and negative voltage clamps to ensure that safe operating
conditions are always maintained over-temperature and loading
conditions.

For example, D1 in Figure 9, functions as a negative voltage
clamp on the AHS pin. Frequently, circuit designers overlook the
negative transients on the xHS pins that occur when the high-side
bridge FET turns off. This rapid di/dt transition of the current
from Q1 to Q2 develops a negative voltage transient as a result
of the parasitic inductance in the low-side FET power current path
(see Figure 10).

R1 on the AHS pin is necessary to limit the current in D1 during
the dead time because without this resistor, D1 is essentially in
parallel with the body diode of Q1. During the dead-time, the
commutating negative current in the body diode results with
approximately a -1.5V conduction voltage (with large amplitude
motor currents). Because the conduction voltage of D1 (~0.6V) is
less than the body diode, R1 limits the current that would flow in

7

FIGURE 10. NEGATIVE TRANSIENT ON xHS

D1 during the dead-time to safe levels. Note that when the
low-side bridge FET is turned on, the negative voltage across the
FET is greatly reduced because the conduction voltage of the FET
channel is typically much less than the conduction voltage of the
body diode. This results with a negative conduction voltage much
less than 0.6V and consequently, significant current flows in D1
only during the dead-time.

C1 in parallel with D1 in Figure 9 is used to reduce the dv/dt on
the xHS pin and also filters high frequency oscillations that occur
on xHS because of parasitic inductance and capacitance on the
this node. Clean transitions on xHS ensures fail safe operation of
the HIP4086 driver.

As an alternative to these capacitors on the xHS pins, the gate
resistors of the bridge FETs can be made larger to lessen the
switching speed but at the expense of more switching losses in
the bridge FETs.

The HIP4086 has a refresh pulse feature that is used to ensure
that the boot caps are biased prior to driving on the high-side
drivers. The refresh pulse occurs only once when bias is applied
to the driver. The refresh feature of the HIP4086 is not really
needed when a programmable controller is used but because
this feature cannot be turned off, C32 is used to ensure noise will
not be a problem with this pin, which is not only an output pin but
also an input.

In this design, the built-in dead time feature of the HIP4086 is
not used (because the microcontroller has a programmable dead
time function set to 1µs. A hardware option on the board does
allow the dead-time function of the HIP4086 to be used if
desired. It can be used to further increase the 1µs programmed
dead-time if desired.

AN1829.0

March 14, 2013

Application Note 1829

U2

R17 R21

R18 R22

R14

R12

R15

R3

5V

ISL28246FUZ

32.4k

FILTER CAPACITORS
ARE NOT SHOWN.

R23 R24

FROM

BRIDGE

0.0150.015

I

MOTOR

+

-

ΩΩ

32.4k

Ω

32.4k

Ω

32.4k

Ω

511

Ω

511

Ω

511

Ω

511

Ω

U2

R17+R21

R18+R22

R12||R14

R15||R3

2.5V

THEV

ISL28246FUZ

Note that re s is to rs la b e le d R x||Ry
represent a parallel equivalent resistor
of Rx and Ry. Rx+Ry represents the
series combination of Rx and Ry.

R23||R24

FROM

BRIDGE

0.0075

I

MOTOR

+

-

1022Ω

Ω

1022

Ω

16.2k

Ω

16.2k

Ω

(EQ. 1)

Vout

CS

=

[(R12||R14)) / (R17+R21)] x I

M

x (R23||R24)+ R3 / (R3+R15) x 5V

(EQ. 2)

VoutCS = [(16.2kΩ))/(1022)] x Im x (0.0075) + 32.4kΩ/(64.8kΩ) x 5V

or
Vout

CS

= 0.119 x IM+2.5V

U3

R4

R1

R12A

ISL28246FUZ

+

-

R38

5V

U3

R11

R39

R12B

ISL28246FUZ

+

-

R11B

5V

I

MOTOR

TO

MICROCONTROLLER

10k

Ω

10k

Ω

10kΩ

10kΩ

249

Ω

1M

Ω

1M

Ω

249

Ω

Please refer to the HIP4086 datasheet for additional application
information.

Current Monitor and Current Limit

There are two current control features in the HIP4086DEMO1Z. A
linear current monitor op amp, U2, amplifies the voltage across
R23 and R24. This op amp is configured as a true differential
amplifier to allow Kelvin connections across the current sensing
resistors (see Figure 11). R15 and R3, each 32.4kΩ, have a
Thevinen equivalent value that is the parallel value of R15 and
R3 (or 1/2 of 32.4kΩ). The Thevinen equivalent voltage also is
1/2 of the bias voltage of 5V. Consequently, the output of the
differential amplifier is offset by +2.5V (see Figure 12).

The output voltage of the differential amplifier is:

where I

is the bridge current (motor current), R12||R14 =

M

R15||R3, and (R17+R21) = (R18+R22) (as required for the
differential amp topology).

Using the defaults values of the HIP4086DEMO1Z:

For 20A, Vout

The I

motor

= 4.878V. For -20A, VoutCS= 0.122V.

CS

signal is monitored by two comparators (see
Figure 13). The output of the upper U3 comparator is biased to
go low when the motor current > 20A. Conversely, the output of
the lower comparator is biased to go low when the motor current
is ≤ 20A.

FIGURE 11. DIFFERENTIAL CURRENT MONITOR AMPLIFIER

FIGURE 12. THEVINEN EQUIVALENT DIFFERENTIAL AMPLIFIER

The current monitor output, I
microcontroller, can be used to control the torque of the motor or
to limit the battery recharging current during regenerative
braking. Because of the offset voltage on the current monitor
output, signals above 2.5VDC represents positive motor current
and signals less that 2.5VDC represent negative motor current.
(Note that this hardware feature is provided for customer use but
is not implemented in the microcontroller firmware.)

MOTOR

, digitized by the

8

FIGURE 13. PULSE-BY-PULSE CURRENT LIMIT COMPARATORS

The OR’ed outputs of these two comparators is monitored by the
microcontroller. Pulse-by-pulse current limiting is provided on
each negative transition. After 256 consecutive pulse limits, all
the bridge FETs are permanently turned off and the current limit
alarm LED (led3) is turned on.

There are two different methods to change the pulse-by-pulse
current limit. The easiest method is to change the value of the
current sensing resistors R23 and R24. For example, removing
R24 halves the pulse by pulse current limit to ± 10A while not
affecting the full scale I

output signal.

motor

Equation 3 calculates the value of the current sensing resistors to
set the pulse-by-pulse current limit at the desired level without
changing the full scale output voltage swing of the I

signal.

MOTOR

AN1829.0

March 14, 2013