STA6940M Brushed DC Motor Driver IC With PWM Control

STA6940M
Brushed DC Motor Driver IC With PWM Control
Features and Benefits
Description
▪ Power supply voltage, VBB , 44 V maximum, 10 to 40 V
normal operating range
▪ Logic supply voltage, VDD , 3 to 5.5 V compatible
▪ Output current, IO ,4 A average, 8 A maximum
▪ Output elements are all N-channel MOSFETs to reduce
losses
▪ Internal charge pump
▪ Forward, reverse, free, and brake control modes available
▪ Constant-current control:
▫ Off-time 35 μs, fixed (Slow Decay mode)
▪ Internal Overcurrent Protection (OCP) circuitry
▫ Off-time 142 μs fixed (Fast Decay mode)
▪ Internal Thermal Shutdown (TSD) circuitry
▪ ZIP type 18-pin fully-molded package (STA package)
Combining low-power CMOS-compatible logic with highcurrent, high-voltage power MOSFET outputs, the STA6940M
provides complete control and drive for brush DC motors.
It provides internal fixed off time, pulse-width modulation
(PWM) control of the output current, rated for 4 A normal
operating level.
The CMOS logic section provides four modes of operation:
forward and reverse normal drive rotation, outputs-off free
spin (coast), and electronic braking.
The innovative multi-chip internal structure separates the main
logic IC (MIC) from the four N-channel power MOSFETs. This
results in lower thermal resistance and greater efficiency.
PWM control allows constant-current control of output while
reducing heat generation and power losses by providing fixed
off-time dual decay modes. The internal charge pump ensures
full power availability for switching.
Package: 18-pin ZIP (STA)
Not to scale
Functional Block Diagram
VDD
CP
7
14
CP1 CP2
13
12
VBB VBB
18
1
MIC
Charge Pump
Reg
UVLO
IN1
IN2
Diag
PWM_REF
OCP_REF
2
3
5
6
Logic
Pre-Driver
17
11
8
9
Comp
Comp
OSC
PWM and
OCP Control
Reg
10
GND
28106.01
16
15
Sense2
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http://www.sanken-ele.co.jp/en/
4
Sense1
OA
OA
OB
OB
STA6940M
Brushed DC Motor Driver IC With PWM Control
Selection Guide
Part Number
Package
Packing
STA6940M
18-pin ZIP through hole mount
*Contact Allegro for additional packing options
18 pieces per tube
Absolute Maximum Ratings
Characteristic
Symbol
Main Supply Voltage
Notes
Rating
Units
44
V
6
V
8
A
VBB
Logic Supply Voltage
VDD
Output Current
IO(max)
≤ 100 μs
Output Voltage
VO
–1.5 to VBB + 1.5
V
Logic Input Voltage
VIN
–0.3 to VDD + 0.3
V
PWM_REF Input Voltage
VPREF
–0.3 to VDD + 0.3
V
OCP_REF Input Voltage
VOREF
Sensing Voltage
VRS
Power Dissipation
PD
Junction Temperature
TJ
Except tw < 1 μs
–0.3 to VDD + 0.3
V
–1 to 2
V
DC drive
2.7
W
PWM drive (Slow Decay)
3.0
W
PWM drive (Fast Decay)
3.2
W
150
ºC
Operating Ambient Temperature
TA
–20 to 85
ºC
Storage Temperature
Tstg
–30 to 150
ºC
Min.
Typ.
Max.
Unit
VBB
10
–
40
V
IO
–
–
4
A
3.0
–
5.5
V
Recommended Operating Conditions
Characteristic
Symbol
Main Supply Voltage
Output Current
Logic Supply Voltage
Conditions
Transient voltages at VDD pin must not
exceed ±0.5 V
VDD
PWM Reference Input Voltage
VPREF
Constant-current control
–
–
1
V
OCP Reference Input Voltage
VOREF
OCP operating
–
–
2
V
Package surface temperature without
heatsink
–
–
85
°C
Case Temperature
TC
Power Derating Curve
Allowable Power Dissipation, PD (W)
3.5
3.2 W
3.0 W
3.0
RQJA = 39°C / W
2.7 W
2.5
RQJA = 42°C / W
2.0
RQJA = 46°C / W
1.5
1.0
DC operation
PWM (Slow Decay)
PWM (Fast Decay)
0.5
0
0
10
20
30
40
50
60
70
80
All performance characteristics given are typical values
for circuit or system baseline design only and are at the
nominal operating voltage and an ambient temperature,
TA, of 25°C, unless otherwise stated.
Ambient Temperature, TA (°C)
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STA6940M
Brushed DC Motor Driver IC With PWM Control
ELECTRICAL CHARACTERISTICS valid at TA = 25°C, VBB = 24 V, VDD = 5 V; unless otherwise noted
Characteristics
Main Supply Current
Symbol
IBB
Logic Supply Current
IDD
Charge Pump Voltage
Vcp
Charge Pump Switching Frequency
Main Supply Undervoltage Protection*
Logic Supply Undervoltage Protection*
Charge Pump Undervoltage Protection*
MOSFET On Resistance
MOSFET Body Diode Forward Voltage
MOSFET Breakdown Voltage
Logic Input Voltage
Logic Input Current
Test Conditions
Operating
VBB = 10 to 40 V
Typ.
Max.
Unit
–
–
20
mA
–
–
5
mA
–
VBB + 5
–
V
fcp
–
360
–
kHz
VUVBL
–
7
–
V
VUVBH
–
7.8
–
V
VUVDL
–
2.3
–
V
VUVDH
–
2.5
–
V
VUVCL
–
3.8
–
V
VUVCH
–
4
–
V
RDS(on)
ID = 4 A
–
0.1
0.13
Ω
VF
IF = 4 A
–
0.95
–
V
VDSS
53
–
–
V
VIL
–
–
0.25 × VDD
V
VIH
0.75 × VDD
–
–
V
IIL
–
±1
–
μA
IIH
Maximum Input Frequency
Min.
fclk
PWM_REF Pin Input Voltage
VPREF
PWM_REF Pin Input Current
IPREF
–
±1
–
μA
Clock duty cycle = 50%
100
–
–
KHz
PWM_REF terminal
0.1
–
1.0
V
–
±10
–
μA
0.1
–
2.0
V
–
±10
–
μA
OCP_REF Pin Input Voltage
VOREF
OCP_REF Pin Input Current
IOREF
PWM Sensing Voltage
VPSEN
Sense1, Sense2 terminals
VPREF –
0.045
VPREF –
0.015
VPREF +
0.015
V
OCP Sensing Voltage
VOSEN
Sense1, Sense2 terminals
VOREF –
0.045
VOREF –
0.015
VOREF +
0.015
V
Sense1, Sense2 Pin Input Current
ISENSE
Sense1, Sense2 terminals
–
±20
–
μA
VDIAGL
IDIAGL = 1.25 mA
–
–
1.25
V
VDIAGH
IDIAGH = –1.25 mA
VDD – 1.25
–
–
V
Diag Pin Output Voltage
Diag Pin Output Current
Diag Pin Output Frequency
OCP_REF terminal
IDIAGL
VDIAGL = 0.5 V
–
–
1.25
mA
IDIAGH
VDIAGH = VDD – 0.5 V
–1.25
–
–
mA
fDIAG
During PWM off-time
–
90
–
kHz
PWM Minimum On-Time (Blanking Time)
ton(min)
–
5
–
μs
PWM Off-Time
tPOFF
PWM operating
–
35
–
μs
OCP Minimum On-Time
tOON
OCP operating
–
5
–
μs
OCP Off-Time
tOOFF
OCP operating
–
142
–
μs
Crossover Current Delay Timing
tCOCD
Switching Time
150
–
750
ns
tcon
Measured from input to output on
–
3.0
–
μs
tcoff
Measured from input to output off
–
2.7
–
μs
–
140
–
ºC
–
115
–
ºC
Thermal Shutdown Activation
Temperature
Ttsdon
Thermal Shutdown Release
Temperature
Ttsdoff
Package back side surface temperature after
case permeated with heat from operation
*The outputs will be disabled if any of the three undervoltage protection circuits are operating.
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STA6940M
Brushed DC Motor Driver IC With PWM Control
Characteristic Data
Output MOSFET On-Voltage, VDS(on)
Output MOSFET Body Diodes Forward Voltage, VF
0.90
MOSFET Body Diode Forward Voltage, VF, (V)
MOSFET On Resaistance, R DS(on), (Ω)
0.17
0.15
0.13
0.11
0.09
0.07
0.05
0
0.85
Single MOSFET
0.80
IO= 4 A
0.75
IO= 3 A
0.70
IO= 2 A
0.65
0.60
IO= 1 A
0.55
0.50
25
50
75
100
125
150
175
0
Junction Temperature, TJ (°C)
28106.01
SANKEN ELECTRIC CO., LTD.
25
50
75
100
125
150
175
Junction Temperature, TJ (°C)
4
STA6940M
Brushed DC Motor Driver IC With PWM Control
Functional Description
Control IC (MIC) Functions
Regulator The regulator supplies the necessary operating power
for the MOSFET gate drivers (see Pre-Driver section) and internal linear circuitry.
UVLO The main supply, logic supply, and charge pump all supply necessary operating power for proper operation. If any one of
the supplies drop to the preset undervoltage lockout threshold, the
outputs will be disabled.
Charge Pump The high-side gate pre-driver for the N-channel
MOSFETs is powered from this charge pump, which operates at
100 kHz.
Pre-Driver This is the gate driver for the output N-channel
MOSFETs. It is powered from the charge pump (high-side) or the
internal regulator (low side).
Current Control and OCP The constant-current control and
overcurrent protection circuitry reference the input voltages on
Table 1. Input Truth Table, PWM Control
Input
Output
OSC The oscillator is used for timing the current-control blanking time and PWM off-time.
Logic I/O Terminals
Motor Control Input Terminals (IN1, IN2) These are used
to control the motor driver outputs to control the behavior of the
motor, as shown in table 1. They have been designed with CMOS
processes to ensure high input impedance. To help mitigate the
effects of noise on these inputs, each terminal is internally fitted
with a low-pass filter. These terminals are designed to be used
with steady logic inputs (low or high).
Diagnostics Output Terminal (Diag) This logic output
indicates normal operation, a fault condition, or PWM output
off-time, as shown in table 2. To avoid damage, the Diag terminal
must not be connected to the GND or supply terminals.
Table 2. Diag Terminal Output
Motor Function
IN1
IN2
OA
OB
Low
Low
High Z
High Z
Free (coast)
High
Low
High
Low
Forward
Low
High
Low
High
Reverse
High
High
Low
Low
Brake
28106.01
the PWM_REF pin (for constant-current level) and OCP_REF
(for overcurrent protection threshold). These functions use a fixed
off-time control scheme.
Output
Indication
High
• No UVLO protection operating
• Outputs ON
Pulse (approximately 90 kHz)
Low
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PWM off-time
• Any UVLO protection operating
• OCP operating
• TSD operating
5
STA6940M
Brushed DC Motor Driver IC With PWM Control
VM
Basic Motor Control Functions
There are four states of motor output: free (coast), forward,
reverse, and brake. This section describes the inputs and the
MOSFET outputs that set these states.
OFF
(A) Free (coast)
Free (Coast) This state is set by low signals on both the IN1 and
the IN2 logic inputs. All MOSFETs are turned off, and no current
flows through the device to the motor. The motor is totally free to
spin. The MOSFET states are shown in figure 1(A).
OFF
OA
Motor
OB
OFF
OFF
Rs
Forward This state is set by a high signal on the IN1 input and
a low signal on the IN2 input. The high-side MOSFET on the
OA side is turned on, and the low-side MOSFET on the OB side
is turned on. Current flows through the device to drive motor
rotation (the terms "forward" and "reverse" only serve to indicate
opposite relative directions). The MOSFET states are shown in
figure 1(B).
VM
ON
(B) Forward
Reverse This state is set by a low signal on the IN1 input and a
high signal on the IN2 input. The low-side MOSFET on the OA
side is turned on, and the high-side MOSFET on the OB side is
turned on. Current flows through the device to drive motor rotation (the terms "forward" and "reverse" only serve to indicate
opposite relative directions). The MOSFET states are shown in
figure 1(C).
Brake This state is set by high signals on both the IN1 and the
IN2 logic inputs. Both high-side MOSFETs are turned off, and
both low-side MOSFETs are turned on. The motor coils are
shorted together providing resistance to rotation. The MOSFET
states are shown in figure 1(D).
OFF
OA
Motor
OB
IM
OFF
ON
Rs
VM
OFF
ON
OA
(C) Reverse
Motor
OB
IM
ON
OFF
Rs
VM
Figure 1. The panels demonstrate the MOSFET switching
conditions and the resulting current flow for each of the
four motor control states.
OFF
OFF
OA
(D) Brake
Motor
ON
OB
ON
Rs
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STA6940M
Brushed DC Motor Driver IC With PWM Control
VM
Constant-Current Control (PWM)
When the motor is starting up, the current, IM , increases to the set
current limit, as shown in figure 2. During operation, the motor
current, IM , is monitored using the voltage across resistor RS ,
which is compared to the set point VPREF.
ONm OFF
When the current limit is reached, the device turns-off the highside MOSFET and body-diode of the low-side MOSFET allows
the back-EMF current to flow in the coil for 35 μs (Slow Decay
mode), as shown in figure 3. After this time expires, the PWM
control reverts to on. There is a blanking time of 5 μs during
turn-on to prevent malfunction due to noise surges. During the
blanking time, the current control does not operate, which means
that the minimum on-time is also the blanking time.
OFF
OA
IM_ON
Motor
OB
Slow Decay: 35 μs
OFF
IM_OFF
ON
Rs
Figure 3. Currrent Control. The current path as current is rising is shown by
the solid arrow (IM_ON), the off-time current is shown by the dashed arrow
(IM_OFF).
Blanking Time
≥5 μ s
Off-Time
35 μs
I PREF
IM
0
VPREF
VRS
0
Diag
0
(A)
(A)
Figure 2. Currrent Control Waveforms. As can be seen at the points (A), PWM
timing and Diag pin oscillation are NOT synchronous.
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STA6940M
Brushed DC Motor Driver IC With PWM Control
Phase PWM Control
The current-control method uses fixed off-time and blanking time,
as detailed above. Even when the PWM_REF terminal is at a low
voltage, however, the current will still flow, and increase, during the blanking time (minimum on-time). This minimal current,
because of the fixed off-time, will only decay to a certain point.
To enable current control below this minimal current level, the
Phase PWM control method must be used. This is different from
the PWM current control as detailed above, and external PWM
signals with the correct on/off duty cycle must be used.
VM
ONm OFF
OFF
OA
IM_ON
Phase PWM control has two modes, Fast Decay mode and Slow
Decay Mode.
Motor
OB
IM_OFF
Fast Decay Mode This mode uses the Free motor state. In other
words, during recirculation time, the IN1 and IN2 pins are both
set low. During motor driving time, the current control point is
determined by the duty cycle and frequency of the input signals:
OFF
ONm OFF
Rs
• The input PWM signals must have an on-duty cycle greater than
50% for proper operation.
• The input PWM signals should have a recommended frequency
of 30 to 50 kHz.
Motor rotation direction is determined by pulsing one or the other
logic input, as shown in table 3. For the forward direction, current
flows are shown in figure 4, and the input pulse and resulting current pulsing is shown in figure 5.
Another new method of control during recirculation, is to change
the inputs shown in table 3, applying low signals instead of high
(the pulsed signals remain as in the table). This method allows the
driver to dissipate less heat by turning on the MOSFET for the
back-EMF current decay instead of using the body diodes. This
method is also known as Synchronous Rectifier control.
Figure 4. Phase PWM control (Fast Decay mode), current flows shown are
for the forward direction
IN1
IN2
IM_ON
IM_OFF
Table 3. Input Truth Table, Phase PWM Control
Input
IN1
IN2
IM_ON
+
IM_OFF
Motor Function
Figure 5. Phase PWM control (Fast Decay mode), logic input pulsing
shown for the forward direction
Fast Decay Mode
PWM pulse
Low
Forward
Low
PWM pulse
Reverse
Slow Decay Mode
PWM pulse
High
Forward
High
PWM pulse
Reverse
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STA6940M
Brushed DC Motor Driver IC With PWM Control
Slow Decay Mode This mode uses the Brake motor state. In
other words, during recirculation time, the IN1 and IN2 pins are
both set high. During motor driving time, the current control
point is determined by the duty cycle and frequency of the input
signals:
• The input PWM signals must have an on-duty cycle less than
50% for proper operation.
• The input PWM signals should have a recommended frequency
of 30 to 50 kHz.
Motor rotation direction is determined by pulsing one or the other
logic input, as shown in table 3. For the forward direction, current
flows are shown in figure 6, and the input pulse and resulting current pulsing is shown in figure 7.
Overcurrent Protection (OCP)
In the STA6940M, the overcurrent protection feature is designed
to protect against rotor lock or coil short conditions. This protection is triggered when the motor current, IM , as detected by the
resistor RS , reaches the set level of OCP_REF.
When the OCP threshold is reached, the driver turns-off all
MOSFETs for 135 μs (figure 8). The decaying current must flow
through the body diodes to the main supply (Fast Decay mode),
as shown in figure 9.
Note: OCP operation does not disable the driver. OCP is flagged
on the Diag pin, and the system logic of the application should
control the response.
VM
IN1
IN2
ONm OFF
OFF
OA
IM_ON
IM_ON
OB
Motor
IM_OFF
OFFm ON
IM_OFF
ON
IM_ON
+
IM_OFF
Rs
Figure 6. Phase PWM control (Slow Decay mode), current flows shown are
for the forward direction
Figure 7. Phase PWM control (Slow Decay mode), logic input pulsing
shown for the forward direction
VM
Off-time
135 μs
IOREF
IM
ONm OFF
OFF
OA
IM_ON
Motor
OB
V
VRS
0
Fast Decay:135 μ s
OFF
IM_OFF
Rs
Figure 8. OCP operation (Fast Decay mode)
28106.01
0
OREF
ONm OFF
Diag
0
Figure 9. OCP operation waveforms (Fast Decay mode)
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9
STA6940M
Brushed DC Motor Driver IC With PWM Control
The constant-current set point, VPREF , and the OCP threshold,
VOREF , may be set individually as needed.
VDD
D iag (V)
• VPREF < VOREF With this relationship, constant-current control
has priority. In order for OCP to operate, the OCP condition
must be detected before the constant-current control is operating, that is, during the blanking time. During blanking time, the
voltage VRS could reach VOREF , initiating OCP.
• VOREF < VPREF With this relationship, OCP has priority over
constant-current control. At any time while the STA6940M is
powered, if the voltage VRS reaches VOREF , OCP can operate.
Thermal Shutdown (TSD)
This device has internal thermal protection. The thermal shutdown function is of the auto-recovery type. The operating principle is that when the internal control IC (MIC) temperature reaches
Ttsdon all outputs are disabled. When the temperature drops below
Ttsdoff the device is reenabled.
Ttsdoff
Ttsdon
TC (°C)
Figure 10. Thermal shutdown operation provides a hysteresis in supply
voltage to the MOSFETs, which is monitored and sets the Diag pin output
When the device outputs are disabled, the function sets the Diag
terminal low. Figure 10 shows the relationship of Diag output and
case temperature, TC.
Note: This device utilizes a multi-chip construction, the Control
IC (MIC) and four separate MOSFETs. The temperature sensor is
located on the control IC, however, the primary heat sources are
the MOSFETs. Thus this internal thermal protection cannot react
to sudden changes in MOSFET temperature.
Undervoltage Protection (UVLO)
If any of the voltages of the main supply, VBB , logic supply,
VDD , or the charge pump, VCP (VCP -VBB), fall below the preset
threshold, the device will be disabled. (The charge pump voltage
is derived from VBB using the internal charge pump circuitry and
connected capacitors.) The effects on output to the motor and to
the Diag pin are shown in figure 11.
Note: The VBB and VDD voltage power-up sequence does not
affect UVLO operation.
28106.01
VDD
VUVDH
0V
VBB
VUVBH
VCP
0V
VUVCH
0V
Diag
0V
Output
Off
Output Output
On
Off
Output
On
Output
Off
Output
On
Figure 11. Operation of the UVLO circuits
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10
STA6940M
Brushed DC Motor Driver IC With PWM Control
Application Information
VDD = 3 to 5.5 V
IN1
CP1 CP2
CP VBB VBB
IN2
M ic ro cont r oller
CB
VDD
VBB = 10 to 40 V
C2
C1
OA
Diag
OA
STA 6940 M
R1
DCM
OCP_ REF
OB
OB
R2
R4 R5
CA
PWM_REF
C3
GND
Sense 2
Sense1
R3
Rs
Logic Gnd
Power Gnd
Figure 12. Typical application circuit
Reference Component Values
R1 = 3 kΩ
R2 = 1 kΩ
R3 = 1 kΩ
R4 = 10 kΩ
R5 = 10 kΩ
*RS = 0.22 Ω
CA = 100 μF / 50 V
CB = 10 μF / 10 V
C1 = 0.1 μF
C2 = 0.1 μF
C3 = 0.1 μF
*Please choose the proper power rating for RS , taking
into consideration the approximate power dissipation, as
2
follows: PD ≈ IO × RS × On Duty Cycle.
• Surge voltage less than -1.0 V may occur on OA and OB
outputs, therefore Schottky barrier diodes are recommended
between those pins and GND
• Please take care to reduce noise on the VDD line.
• Logic input terminals (IN1 and IN2) which are not externally
controlled must not be left open; they should be pulled-up or
pulled-down to the VDD or GND terminals, based on the required mode. Otherwise the device may malfunction.
• Noise voltages greater than 0.5 V on the VDD line may cause
malfunction. Please take special care when laying out the return
line and ground pattern.
• Unused logic output terminals (Diag) should be left open.
• Separating IC GND (pin 10), VDD Gnd (signal ground) and
VBB Gnd (power ground) helps reduce noise.
• Connecting only one of the Sensex terminals may result in damage to the device.
28106.01
• The Sense1 and Sense2 terminals must be tied together, and
then connected to RS .
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11
STA6940M
Brushed DC Motor Driver IC With PWM Control
PWM Constant-Current Control Setting (R1, R2, R3, RS)
The PWM fixed current control set point may be changed by
using resistors R1, R2, R3 and RS as shown in figure 12.
The formula for calculating Io is as follows:
constant-current, but using VOREF:
IOCP = VOREF / RS ,
where
IO = VPREF / RS ,
(1)
VOREF =
where
VPREF =
R3
R1 + R2 + R3
× VDD
(3)
(2)
.
If VPREF is set below 0.1 V, external factors such as component
tolerance and wiring impedances may affect the accuracy of the
set current level.
The STA6940M uses a fixed off-time control scheme. During
the off-time, the energy stored in the motor coils dissipates. If
the set current point is too low, the motor current may become
discontinuous and the motor torque will be greatly reduced as a
result. Please take this into consideration when setting the minimal current level. Although setting such a low current level does
not damage the device, the control of the set current level will
become worse. This is illustrated in figure 13.
OCP Point Setting
The formula for setting the OCP point is the similar to that for
R2 +R3
R1 + R2 + R3
× VDD
.
(4)
Power Supply (VBB, VDD) On/Off Sequence
This device will operate normally regardless of the power-up
sequence of the power supplies.
Internal Logic Circuitry Connection
The following guidelines should be followed when connecting the
internal circuitry:
• Input Logic Terminals (IN1, IN2) These terminals require a
fixed logic level, and when they are unused, they should not be
left open. They should be connected to VDD or GND as necessary.
• Output Terminal (Diag) The Diag terminal has an internal equivalent circuit as shown in figure 14. Because this is
a CMOS circuit structure, if the terminal is not being used it
should be left open.
VDD
STA6940M
ESD
protection
circuitry
Output, Ox
Large ITRIP
VRS
0
Small ITRIP
Coil current = 0
Figure 13. Minimum controllable current level
28106.01
Figure 14. Diag terminal equivalent circuit
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12
Brushed DC Motor Driver IC With PWM Control
Thermal Considerations
To accurately calculate the losses incurred by the STA6940M,
detailed knowledge of the motor characteristics, input waveforms,
and dynamic properties of the circuit must all be considered. The
formulas below are simplified approximations using worst-case
conditions:
For constant voltage drive (DC current):
2 Channels, Steady DC Operation
140
120
ΔTJA = 46 × PD
100
ΔTJ (°C)
STA6940M
80
60
ΔTJA = 35 × PD
40
PD = IO2 × RDS(on) × 2 ,
(5)
20
0
and, for constant-current drive (PWM):
PD =
IO2 ×
RDS(on) × 2 ×
0
tON
tON + tOFF
+ ( IO2 × RDS(on) + VF × IO ) ×
0.5
1.0
1.5
2.0
PD (W)
2.5
3.0
3.5
3 Channels, PWM Operation (Slow Decay)
tOFF
tON + tOFF
,
140
(6)
120
where:
ΔTJA = 42 × PD
100
ΔTJ (°C)
PD is the device power dissipation,
IO is the motor current ( ≈ IO),
RDS(on) is the internal MOSFET on-resistance,
80
60
ΔTJA = 35 × PD
40
RS is the external sensing resistor,
20
VF is the internal MOSFET body diode forward voltage,
0
tON is the PWM on-time, and
0
0.5
1.0
tOFF is the PWM off-time.
1.5
2.0
2.5
3.0
3.5
PD (W)
If a heatsink is being used, the ΔTJA (junction to ambient) as
calculated previously will be different because the thermal resistance, RθJA , is different. The new value can be calculated using
the heatsink heat resistance RθFIN:
4 Channels, PWM Operation (Fast Decay)
140
120
ΔTJA = 39 × PD
100
ΔTJ (°C)
Using the above calculated power dissipation, it is possible to
estimate the junction temperature using the curves in figure 15. In
the worst conditions (with high ambient temperatures), as long as
the junction temperature does not exceed 150ºC the device will
not be damaged. However, the actual temperature of the device
should be measured along with the junction temperature calculation.
80
60
ΔTJA = 35 × PD
40
20
0
0
RQJA z RQJC + RQFIN = (RQJA – RQCA) + RQFIN
.
(7)
0.5
1.0
1.5
2.0
2.5
3.0
3.5
PD (W)
Figure 15. Change in junction temperature versus device power dissipation
28106.01
SANKEN ELECTRIC CO., LTD.
13
STA6940M
Brushed DC Motor Driver IC With PWM Control
To extrapolate the junction temperature, ΔTJ , using a measured
device temperature, please use the following method:
1. Measure the ambient temperature, TA.
2. With the device mounted but not operating, measure the surface
temperature of the device on the back side at the center.
3. Power-on the device, and after it reaches operating temperature,
take the measurement again.
4. Subtract the value found in step 2 from the value found in step 3.
This provides a value for ΔTCA .
5. Refer to figure 15 and locate the value found in step 4 on the
ΔTCA trace.
6. Determine the corresponding power dissipation, PD.
28106.01
7. Substitute the values into the following equation:
∆TJ ∆TCA + PD × RQJC
.
(8)
Important notes:
• Please ensure that the maximum rated junction temperature
(150ºC) will not be exceeded.
• The information provided above is to be used as reference for
the design phase. The actual product must undergo empirical
testing to ensure proper thermal design.
• The recommended maximum operating temperature for this
device, without a heatsink is TC = 80ºC maximum.
SANKEN ELECTRIC CO., LTD.
14
STA6940M
Brushed DC Motor Driver IC With PWM Control
Pin-out Diagram
2
1
Chamfer
4
3
6
5
8
7
10
9
12
11
14
13
16
15
18
17
(Top View)
Terminal List Table
Number
Symbol
1
VBB
2
3
OA
4
Sense1
5
IN1
6
IN2
7
VDD
8
PWM_REF
Function
Main supply input (motor supply)
Motor terminal A
Motor current sensing
Control mode setting (please see truth table)
Logic supply
Constant-current setting
9
OCP_REF
10
GND
Ground
PWM diagnostic and OCP output
11
Diag
12
CP2
13
CP1
14
CP
15
Sense2
16
17
18
Overcurrent setting
Connection for charge pump
Motor overcurrent sensing
OB
Motor terminal B
VBB
Main supply input (motor supply)
*The VBB terminals, 1 and 18, are internally connected.
28106.01
SANKEN ELECTRIC CO., LTD.
15
STA6940M
Brushed DC Motor Driver IC With PWM Control
Package Outline Drawing
25.55
(Includes mold flash)
25.25 ±0.3
Gate protrusion
4 ±0.2
Gate protrusion
9.0 ±0.2
1 REF
Branding Area
3.3 ±0.5
6.9 REF
3.6
REF
1.3 ±0.1 B
R1 REF
+0.2
0.45 – 0.1
0.55 +0.2
– 0.1
2X1.5 ±0.5
1
3
2
A
Measured at pin tips
B
Measured at case base
5
4
7
6
9
8
11
10
1.27 ±0.5 A
13
12
15
14
2.54 ±0.5 A
17
16
18
Terminal core material: Cu
Terminal plating: Ni, with Pb-free solder coating
Dimensions in millimeters
Branding codes (exact appearance at manufacturer discretion):
1st line, type: STA6940M
2nd line, lot:
YMDD
Where: Y is the last digit of the year of manufacture
M is the month (1 to 9, O, N, D)
DD is the date
Leadframe plating Pb-free. Device composition
includes high-temperature solder (Pb >85%),
which is exempted from the RoHS directive.
28106.01
SANKEN ELECTRIC CO., LTD.
16
STA6940M
Brushed DC Motor Driver IC With PWM Control
Because reliability can be affected adversely by improper storage
environments and handling methods, please observe the following
cautions.
Cautions for Storage
•
Ensure that storage conditions comply with the standard
temperature (5°C to 35°C) and the standard relative humidity
(around 40 to 75%); avoid storage locations that experience
extreme changes in temperature or humidity.
•
Avoid locations where dust or harmful gases are present and
avoid direct sunlight.
•
Reinspect for rust on leads and solderability of products that have
been stored for a long time.
Cautions for Testing and Handling
When tests are carried out during inspection testing and other
standard test periods, protect the products from power surges
from the testing device, shorts between adjacent products, and
shorts to the heatsink.
Remarks About Using Silicone Grease with a Heatsink
• When silicone grease is used in mounting this product on a
heatsink, it shall be applied evenly and thinly. If more silicone
grease than required is applied, it may produce stress.
• Coat the back surface of the product and both surfaces of the
insulating plate to improve heat transfer between the product and
the heatsink.
• Volatile-type silicone greases may permeate the product and
produce cracks after long periods of time, resulting in reduced
heat radiation effect, and possibly shortening the lifetime of the
product.
• Our recommended silicone greases for heat radiation purposes,
which will not cause any adverse effect on the product life, are
28106.01
indicated below:
Type
Suppliers
G746
Shin-Etsu Chemical Co., Ltd.
YG6260
Momentive Performance Materials, Inc.
SC102
Dow Corning Toray Silicone Co., Ltd.
Soldering
•
When soldering the products, please be sure to minimize the
working time, within the following limits:
260±5°C 10 s
350±5°C
•
3s
Soldering iron should be at a distance of at least 1.5 mm from the
body of the products
Electrostatic Discharge
•
When handling the products, operator must be grounded.
Grounded wrist straps worn should have at least 1 MΩ of
resistance to ground to prevent shock hazard.
•
Workbenches where the products are handled should be
grounded and be provided with conductive table and floor mats.
•
When using measuring equipment such as a curve tracer, the
equipment should be grounded.
•
When soldering the products, the head of soldering irons or the
solder bath must be grounded in other to prevent leak voltages
generated by them from being applied to the products.
•
The products should always be stored and transported in our
shipping containers or conductive containers, or be wrapped in
aluminum foil.
SANKEN ELECTRIC CO., LTD.
17
STA6940M
Brushed DC Motor Driver IC With PWM Control
• The contents in this document are subject to changes, for improvement and other purposes, without notice. Make sure that this is the
latest revision of the document before use.
• Application and operation examples described in this document are quoted for the sole purpose of reference for the use of the products herein and Sanken can assume no responsibility for any infringement of industrial property rights, intellectual property rights or
any other rights of Sanken or any third party which may result from its use.
• Although Sanken undertakes to enhance the quality and reliability of its products, the occurrence of failure and defect of semiconductor products at a certain rate is inevitable. Users of Sanken products are requested to take, at their own risk, preventative measures
including safety design of the equipment or systems against any possible injury, death, fires or damages to the society due to device
failure or malfunction.
• Sanken products listed in this document are designed and intended for the use as components in general purpose electronic equipment or apparatus (home appliances, office equipment, telecommunication equipment, measuring equipment, etc.).
When considering the use of Sanken products in the applications where higher reliability is required (transportation equipment and
its control systems, traffic signal control systems or equipment, fire/crime alarm systems, various safety devices, etc.), and whenever
long life expectancy is required even in general purpose electronic equipment or apparatus, please contact your nearest Sanken sales
representative to discuss, prior to the use of the products herein.
The use of Sanken products without the written consent of Sanken in the applications where extremely high reliability is required
(aerospace equipment, nuclear power control systems, life support systems, etc.) is strictly prohibited.
• In the case that you use Sanken products or design your products by using Sanken products, the reliability largely depends on the
degree of derating to be made to the rated values. Derating may be interpreted as a case that an operation range is set by derating the
load from each rated value or surge voltage or noise is considered for derating in order to assure or improve the reliability. In general,
derating factors include electric stresses such as electric voltage, electric current, electric power etc., environmental stresses such
as ambient temperature, humidity etc. and thermal stress caused due to self-heating of semiconductor products. For these stresses,
instantaneous values, maximum values and minimum values must be taken into consideration.
In addition, it should be noted that since power devices or IC's including power devices have large self-heating value, the degree of
derating of junction temperature affects the reliability significantly.
• When using the products specified herein by either (i) combining other products or materials therewith or (ii) physically, chemically
or otherwise processing or treating the products, please duly consider all possible risks that may result from all such uses in advance
and proceed therewith at your own responsibility.
• Anti radioactive ray design is not considered for the products listed herein.
• Sanken assumes no responsibility for any troubles, such as dropping products caused during transportation out of Sanken's distribution network.
• The contents in this document must not be transcribed or copied without Sanken's written consent.
28106.01
SANKEN ELECTRIC CO., LTD.
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