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3-Phase DC Brushless Motor Pre-Drivers
Technical Information
NJM2626
1.FEATURE
The NJM2626 is a controller and pre-driver for speed control 3-phase blushless DC motor. The device
provides the proper sequencing of 3-phase drive output with external hall ICs inputs.(120degree turn-on
mode)
It is possible to control of 3-phase blushless DC motor by added external output buffers.
The device has totem-pole pre-drivers for external power MOS transistors and therefore can make the
target output motor driver by using suitable power elements.
Further more the device has PWM control ,forward-reverse rotation and current limiting function.
2. Application Circuit
The application shown in below circuit is designed for an open loop motor speed control system that the
upper power switch are P-Channel power MOSFET while the lower switches are N-Channel power
MOSFET.
MOSFET drive (Upper:Pch ,Lower:Nch),Lower side PWM
Operating Vcc:12V, supply Vm:12V
VM
FR
NJM2626
H1
UH
Rotor
Position
Decode
H2
VH
H3
VCC
WH
VCC
Vref
Vref
Motor
UVLO
UL
Saw
Osillator
OSC
Logic
VL
+
Verr
+
-
-
GND
WL
+
-
ILimit
1
’08.07.29
3-Phase DC Brushless Motor Pre-Drivers
Technical Information
NJM2626
3. Terminal Functions
(3-1) UH, VH, WH
It consists of Sink-type transistor and controls the upper P-Channel power MOSFET.
The upper side GATE bias current is generated with connected Inverting transistor and resistor.
Regarding design case at Vgs=10V, Isink=20mA about the GATE bias voltage of P-Channel power
MOSFET.
Rgl + Rg 2 =
12V
12
=
= 6ooΩ
I sin k 0.02
Vgs = Rgl × I sin k = 500 × 0.02 = 10V
The values of Rg1 and Rg2 should be 500Ω, 100Ω.
(3-2) UL, VL, WL
It consists of totem-pole pre-driver and control the lower N-Channel power MOSFET. It is possible to
make motor speed control by PWM control. Series GATE resistor Rg3 will damp any high frequency
oscillations caused by the MOSFET input capacitance and any series wiring induction in the gate-source
circuit.
(3-3) H1, H2, H3
It is the signal input terminal of the Hall IC that is the sensor of rotor magnetic pole position of the motor.
The internal circuit decodes these 3 magnetic position signals to120-degree energization logics
About the relation of H1~H3 (the Hall device input) to UH~WH or UL~WL (that controls ON-OFF of
3-phase MOSFET Bridge), please refer to the below.
The relation between Hall inputs and commutation logic outputs is as follows.
Commutation logic truth table
Hall Inputs
Outputs
F/R=L
F/R=H
H1
H2
H3
H1
H2
H3
UH
VH
WH
UL
VL
WL
H
L
H
L
H
L
X
L
X
H
L
L
H
L
L
L
H
H
X
X
L
H
L
L
H
H
L
L
L
H
X
X
L
L
H
L
L
H
L
H
L
H
L
X
X
L
H
L
L
H
H
H
L
L
L
X
X
L
L
H
L
L
H
H
H
L
X
L
X
L
L
H
L
L
L
L
L
L
X
X
X
L
L
L
H
H
H
H
H
H
X
X
X
L
L
L
The information of the timing chart is shown in attached (5-1)
-2-
3-Phase DC Brushless Motor Pre-Drivers
Technical Information
NJM2626
(3-4) F/R
It is the motor rotation direction input terminal and is controllable by setting the terminal to "H" or "L." A
rotation direction change must be made after motor stopped completely.
In such case, switching elements will generate a vertical arm short circuit and it may cause destruction of
the switching devices.
However, if PWM is closed before and after a rotation direction change (Verr<0.35V), a rotation direction
can be performed safely.
In order to improve the noise resistance, it employs hysteresis input circuit.
The range of input voltage: 0v~Vref
The relation between F/R input and the motor rotation direction is as follows.
F/R Input and Motor Rotation
F/R
Direction
L
U⇒V⇒W
H
U⇒W⇒V
(3-5) ILIMIT
It is the motor current detection terminal. It allows the control of the torque limiter function, the startup with
the soft-start and the current when the motor is constrained. The motor current is converted to a voltage
by inserting a ground-referenced sense resistor Rs in series with the three lower MOSFETs. The voltage
developed across the sense resistor is monitored by ILIMIT terminal, and compared to the internal Sense
Voltage(Vth).
If the current sense is exceeded, the comparator sets the over-current latch and terminates the PWM
output.
Over-current detection is reset for every cycle of the internal Oscillator.
The value for over-current detection is:
I=
Vth
Rs
When an over-current detection function is not well detected by the noise etc., the addition of the
RC filter will eliminate current-limit instability by the leading edges spike on the current waveform.
(3-6) Vref
It is the output terminal of internal reference voltage. This terminal please inserts capacitor between GND
for stabilization. (We recommend capacitor value is 1µF.)
-3-
3-Phase DC Brushless Motor Pre-Drivers
Technical Information
NJM2626
(3-7) Verr
It is the motor speed control terminal.
The range of input voltage : 0V~Vref
Control approach for Output duty is
Analogue voltage control
Input voltage is compared with internal triangular wave voltage.
Verr input voltage: less or equal 0.9V (typ.), duty 0%
: greater and or equal 2.8V(typ.), duty 100%
or
Pulse voltage control
Verr input voltage: 0.35V (max.), PWM 0%
: 3.5V (min), PWM 100%
(3-8) OSC
By connecting a capacitor to this terminal, the internal Oscillation frequency is decided.
Frequency is set to about 25kHz when capacitor value is 1000pF. If frequency is low, the switching
sound from a motor will occur, and if high, the switching loss of a Power element will increase.
We recommend selection with a frequency of 20 to 30kHz.
-4-
3-Phase DC Brushless Motor Pre-Drivers
Technical Information
NJM2626
4. Protection circuit
(4-1)UVLO
UVLO timing chart
⊿UVLO
Vcc
5.45V(typ
)
5.0V(typ.):UVLO
UH/VH/WH
UL/VL/WL
UVLO Operation Section
UH/VH/WH output: Hi-Z
UL/VL/WL output voltage: Low
(4-2) Overcurrent detecting circuit
OC timing chart
Vposc:2.8Vtyp.
OSC
OSC
Vbosc:0.9Vtyp.
Verr
Internal
CLOCK
Vth:0.5Vtyp.
I Limit
UL/VL/WL
OC reset
OC detection
-5-
3-Phase DC Brushless Motor Pre-Drivers
Technical Information
NJM2626
5. Appendix
(5-1) The timing chart of Hall input and pre-driver output
FR:L Forward Rotation
H1
H2
H3
UH
VH
WH
UL
VL
WL
FR:H Reverse Rotation
H1
H2
H3
UH
VH
WH
UL
VL
WL
-6-
3-Phase DC Brushless Motor Pre-Drivers
Technical Information
NJM2626
(5-2)Closed Loop speed control circuit
Speed control circuit is shown as following figure. This circuit consists of input buffer, Level shifter
and Speed control amplifier. Motor speed can be changed by “speed set” VR. VR1 is trimmer for
final stage gain for stability. NJM13403 is quad single supply general-purpose operational amplifier.
The typical values of the other parts are shown in figure.
Vcc=12V
0.1u
82k
10k
from
NJM2626 H1 ,H2 or H3
FG
0.47u
2k
10k
to Verr
VR1
2k
4.7u
10u
47k
speed set
Opamp:NJM13403
An example circuit of 3 multiple FG_OUT using H1,H2 and H3 is shown below.
H1
Vcc=12V
H2
H3
FG OUT
H1
H2
H3
FG OUT
-7-
3-Phase DC Brushless Motor Pre-Drivers
Technical Information
NJM2626
(5-3)Example of a short brake circuit
5V
10k
10k
SB
30k
+
-
-
2k
10k
Verr
+
0.01u
SB
10k
Verr
comparator
NJM2901
sb
10k
30us
110us
-
sb
+
30k
sb
Rg1
1:FR
Rg2
NJM2626
3:H1
15:UH
Rotor
Position
Decode
4:H2
14:VH
5:H3
16:VCC
13:WH
VCC
2:Vref
Vref
UVLO
1u
12:UL
6:OSC
Saw
Osillator
Logic
11:VL
1000p
+
Hi
10k
7:Verr
+
Low
Verr
8:GND
-
-
10:WL
+
-
9:ILimit
-8-
Rg3
3-Phase DC Brushless Motor Pre-Drivers
Technical Information
NJM2626
(5-4) 24V power supply
In the case of using 24V power supply
The gate bias resistance of Pch-MOSFET of Upper arm device is designed based on (3-1).
About the gate voltage of Nch-MOSFET of Lower arm device, in consideration of rating of the gate
source of Nch-MOSFET, terminals (UL~WL) are redundant circuit, output voltage 20V(max.),
Vcc=26V.
(5-5) Upper arm device: Nch-MOSFET
Example of the Circuit construction of external 3-Phase Bridge device (Nch-MOSFET)
It needs 10V power supply for Nch-MOSFET gate driver in addition to power supply for motor (VM).
10V
VM
1:FR
NJM2626
3:H1
15:UH
Rotor
Position
Decode
4:H2
14:VH
5:H3
16:VCC
13:WH
VCC
2:Vref
Vref
Motor
UVLO
12:UL
6:OSC
Saw
Osillator
Logic
11:VL
+
7:Verr
+
-
8:GND
10:WL
+
-
9:ILimit
-9-
3-Phase DC Brushless Motor Pre-Drivers
Technical Information
NJM2626
(5-6) fosc vs. OSC-Capacitor
NJM2626
fosc vs. OSC-Capacitor
VCC=12V
Verr=2.2V
Ta=25degC
fosc [kHz]
100
10
10
100
1000
10
4
OSC Capacitor [pF]
[CAUTION]
The specifications on this databook are only
given for information , without any guarantee
as regards either mistakes or omissions. The
application circuits in this databook are
described only to show representative usages
of the product and not intended for the
guarantee or permission of any right including
the industrial rights.
- 10 -
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