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STA6940M Brushed DC Motor Driver IC With PWM Control
Features and Benefits
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 s, fixed (Slow Decay mode) Internal Overcurrent Protection (OCP) circuitry Off-time 142 s fixed (Fast Decay mode) Internal Thermal Shutdown (TSD) circuitry ZIP type 18-pin fully-molded package (STA package)
Package: 18-pin ZIP (STA)
Description
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.
Not to scale
Functional Block Diagram
VDD 7 CP 14 CP1 CP2 13 12 VBB VBB 18 1
MIC Charge Pump UVLO IN1 IN2 Diag PWM_REF OCP_REF 5 6 11 8 Comp PWM and OCP Control OSC Reg Logic Pre-Driver Reg 2 3 16 17
OA OA OB OB
9
Comp
10 GND
15 Sense2
4 Sense1
28106.01
STA6940M
Selection Guide
Part Number
Brushed DC Motor Driver IC With PWM Control
Package Packing
18 pieces per tube
STA6940M 18-pin ZIP through hole mount *Contact Allegro for additional packing options
Absolute Maximum Ratings
Characteristic Main Supply Voltage Logic Supply Voltage Output Current Output Voltage Logic Input Voltage PWM_REF Input Voltage OCP_REF Input Voltage Sensing Voltage Power Dissipation Junction Temperature Operating Ambient Temperature Storage Temperature Symbol VBB VDD IO(max) VO VIN VPREF VOREF VRS PD TJ TA Tstg Except tw < 1 s DC drive PWM drive (Slow Decay) PWM drive (Fast Decay) 100 s Notes Rating 44 6 8 -1.5 to VBB + 1.5 -0.3 to VDD + 0.3 -0.3 to VDD + 0.3 -0.3 to VDD + 0.3 -1 to 2 2.7 3.0 3.2 150 -20 to 85 -30 to 150 Units V V A V V V V V W W W C C C
Recommended Operating Conditions
Characteristic Main Supply Voltage Output Current Logic Supply Voltage PWM Reference Input Voltage OCP Reference Input Voltage Case Temperature Symbol VBB IO VDD VPREF VOREF TC Transient voltages at VDD pin must not exceed 0.5 V Constant-current control OCP operating Package surface temperature without heatsink Conditions Min. 10 - 3.0 - - - Typ. - - - - - - Max. 40 4 5.5 1 2 85 Unit V A V V V C
Power Derating Curve
3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 DC operation PWM (Slow Decay) PWM (Fast Decay) 0 10 20 30 40 50 60 70 80 R
JA
3.2 W 3.0 W 2.7 W
R
JA
= 39C / W
Allowable Power Dissipation, PD (W)
= 42C / W R
JA
= 46C / W
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 25C, unless otherwise stated.
Ambient Temperature, TA (C)
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
2
STA6940M
Characteristics Main Supply Current Logic Supply Current Charge Pump Voltage Charge Pump Switching Frequency
Brushed DC Motor Driver IC With PWM Control
Symbol IBB IDD Vcp fcp VUVBL VUVBH VUVDL VUVDH VUVCL VUVCH RDS(on) VF VDSS VIL VIH IIL IIH fclk VPREF IPREF VOREF IOREF VPSEN VOSEN ISENSE VDIAGL VDIAGH IDIAGL IDIAGH fDIAG ton(min) tPOFF tOON tOOFF tCOCD tcon tcoff Ttsdon Ttsdoff Measured from input to output on Measured from input to output off Package back side surface temperature after case permeated with heat from operation PWM operating OCP operating OCP operating Sense1, Sense2 terminals Sense1, Sense2 terminals Sense1, Sense2 terminals IDIAGL = 1.25 mA IDIAGH = -1.25 mA VDIAGL = 0.5 V VDIAGH = VDD - 0.5 V During PWM off-time OCP_REF terminal Clock duty cycle = 50% PWM_REF terminal ID = 4 A IF = 4 A VBB = 10 to 40 V Operating Test Conditions Min. - - - - - - - - - - - - 53 - 0.75 x VDD - - 100 0.1 - 0.1 - VPREF - 0.045 VOREF - 0.045 - - VDD - 1.25 - -1.25 - - - - - 150 - - - - Typ. - - VBB + 5 360 7 7.8 2.3 2.5 3.8 4 0.1 0.95 - - - 1 1 - - 10 - 10 VPREF - 0.015 VOREF - 0.015 20 - - - - 90 5 35 5 142 - 3.0 2.7 140 115 Max. 20 5 - - - - - - - - 0.13 - - 0.25 x VDD - - - - 1.0 - 2.0 - VPREF + 0.015 VOREF + 0.015 - 1.25 - 1.25 - - - - - - 750 - - - - Unit mA mA V kHz V V V V V V V V V V A A KHz V A V A V V A V V mA mA kHz s s s s ns s s C C
ELECTRICAL CHARACTERISTICS valid at TA = 25C, VBB = 24 V, VDD = 5 V; unless otherwise noted
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 Maximum Input Frequency PWM_REF Pin Input Voltage PWM_REF Pin Input Current OCP_REF Pin Input Voltage OCP_REF Pin Input Current PWM Sensing Voltage OCP Sensing Voltage Sense1, Sense2 Pin Input Current Diag Pin Output Voltage Diag Pin Output Current Diag Pin Output Frequency PWM Minimum On-Time (Blanking Time) PWM Off-Time OCP Minimum On-Time OCP Off-Time Crossover Current Delay Timing Switching Time Thermal Shutdown Activation Temperature Thermal Shutdown Release Temperature
*The outputs will be disabled if any of the three undervoltage protection circuits are operating.
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
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STA6940M
Brushed DC Motor Driver IC With PWM Control
Characteristic Data
Output MOSFET On-Voltage, VDS(on)
0.17 MOSFET Body Diode Forward Voltage, VF, (V) MOSFET On Resaistance, R DS(on), ()
Output MOSFET Body Diodes Forward Voltage, VF
0.90 0.85 Single MOSFET 0.80 IO= 4 A 0.75 0.70 0.65 0.60 IO= 1 A 0.55 0.50 IO= 3 A IO= 2 A
0.15
0.13
0.11
0.09
0.07
0.05 0
25
50
75
100
125
150
175
0
25
50
75
100
125
150
175
Junction Temperature, TJ (C)
Junction Temperature, TJ (C)
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
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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
the PWM_REF pin (for constant-current level) and OCP_REF (for overcurrent protection threshold). These functions use a fixed off-time control scheme. 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 1. Input Truth Table, PWM Control
Input IN1 Low High Low High IN2 Low Low High High Output OA High Z High Low Low OB High Z Low High Low Motor Function Free (coast) Forward Reverse Brake
Table 2. Diag Terminal Output
Output High Pulse (approximately 90 kHz) Low Indication * No UVLO protection operating * Outputs ON PWM off-time * Any UVLO protection operating * OCP operating * TSD operating
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
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. 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). 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). 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
OFF OA
(A) Free (coast)
Motor
OB
OFF
OFF
Rs
VM
ON OA
OFF
(B) Forward
Motor
IM
OB
OFF
ON
Rs
VM
OFF OA
ON
(C) Reverse
Motor
IM
OB
ON Rs
OFF
VM
Figure 1. The panels demonstrate the MOSFET switching conditions and the resulting current flow for each of the four motor control states.
OFF OA
OFF
(D) Brake
Motor
OB
ON Rs
ON
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
6
STA6940M
Brushed DC Motor Driver IC With PWM Control
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. 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 s (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 s 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.
ON OFF OA IM_ ON
VM
OFF
Motor
OB
Slow Decay: 35 s 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).
Off-Time 35 s
Blanking Time 5 s
I PREF IM 0
VRS 0
VPREF
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.
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
7
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. Phase PWM control has two modes, Fast Decay mode and Slow Decay Mode. 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: * 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.
VM
ON
OFF
OFF OA IM_ ON
Motor
IM_OFF
OB
OFF
ON
OFF
Rs
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 PWM pulse Low PWM pulse High IN2 Fast Decay Mode Low PWM pulse Slow Decay Mode High PWM pulse Forward Reverse Forward Reverse Motor Function
IM_ ON + IM_ OFF Figure 5. Phase PWM control (Fast Decay mode), logic input pulsing shown for the forward direction
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
8
STA6940M
Brushed DC Motor Driver IC With PWM Control
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 s (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.
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.
VM
IN1 IN2
ON OFF
OFF OA IM_ ON
Motor
OB
IM_ ON
IM_ OFF
OFF ON
IM_ OFF Rs
ON
IM_ ON + IM_ OFF Figure 7. Phase PWM control (Slow Decay mode), logic input pulsing shown for the forward direction
Figure 6. Phase PWM control (Slow Decay mode), current flows shown are for the forward direction
VM
Off-time 135 s IOREF
ON
OFF
IM
OFF OA IM_ ON
0 V VRS 0 OREF
Motor
OB
Fast Decay:135 s OFF IM_ OFF
ON OFF
Rs
Diag 0
Figure 8. OCP operation (Fast Decay mode)
Figure 9. OCP operation waveforms (Fast Decay mode)
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
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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. * 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. 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.
VDD VUVDH 0V VUVBH 0V VUVCH 0V Diag 0V Output Off Output Output On Off Output On Output Off Output On
VDD D iag (V)
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
VBB VCP
Figure 11. Operation of the UVLO circuits
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
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STA6940M
Brushed DC Motor Driver IC With PWM Control
Application Information
VDD = 3 to 5.5 V
C1
C2
VBB = 10 to 40 V
IN1 M ic ro cont r oller IN2 Diag R1
VDD
CP1 CP2
CP VBB VBB
OA OA STA 6940 M DCM OB OB CA
CB
OCP_ REF R4 R5 C3 R3 Rs R2 PWM_REF GND Sense 2
Sense1
Logic Gnd Figure 12. Typical application circuit
Power Gnd
Reference Component Values
R1 = 3 k R2 = 1 k R3 = 1 k R4 = 10 k R5 = 10 k *RS = 0.22 CA = 100 F / 50 V CB = 10 F / 10 V C1 = 0.1 F C2 = 0.1 F C3 = 0.1 F
*Please choose the proper power rating for RS , taking into consideration the approximate power dissipation, as 2 follows: PD IO x RS x 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. * 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. * Separating IC GND (pin 10), VDD Gnd (signal ground) and VBB Gnd (power ground) helps reduce noise.
* 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. * Unused logic output terminals (Diag) should be left open. * The Sense1 and Sense2 terminals must be tied together, and then connected to RS . * Connecting only one of the Sensex terminals may result in damage to the device.
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
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:
IO = VPREF / RS ,
constant-current, but using VOREF:
IOCP = VOREF / RS ,
(3)
where (1)
VOREF = R2 +R3 R1 + R2 + R3 x VDD
.
(4)
where
VPREF = R3 R1 + R2 + R3 x VDD
.
(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
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
VRS 0 Large ITRIP Small ITRIP Coil current = 0
Output, Ox
Figure 13. Minimum controllable current level
Figure 14. Diag terminal equivalent circuit
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
12
STA6940M
Brushed DC Motor Driver IC With PWM Control
TJ (C)
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 PD = IO x RDS(on) x 2 ,
2 Channels, Steady DC Operation 140 120 100 80 60 40 TJA = 35 x PD TJA = 46 x PD
(5)
20 0 0 0.5 1.0 1.5 2.0 PD (W) 2.5 3.0 3.5
and, for constant-current drive (PWM):
PD =
2 IO x
RDS(on) x 2 x
tON tON + tOFF tOFF tON + tOFF
,
2 + ( IO x RDS(on) + VF x IO ) x
3 Channels, PWM Operation (Slow Decay)
(6)
140 120 100 TJ (C) 80 60 40 20 0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 PD (W) 140 120 100 TJ (C) 80 60 40 20 0 0 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 TJA = 35 x PD 4 Channels, PWM Operation (Fast Decay) TJA = 35 x PD TJA = 42 x PD
where: PD is the device power dissipation, IO is the motor current ( IO), RDS(on) is the internal MOSFET on-resistance, RS is the external sensing resistor, VF is the internal MOSFET body diode forward voltage, tON is the PWM on-time, and tOFF is the PWM off-time. 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 150C the device will not be damaged. However, the actual temperature of the device should be measured along with the junction temperature calculation. If a heatsink is being used, the TJA (junction to ambient) as calculated previously will be different because the thermal resistance, RJA , is different. The new value can be calculated using the heatsink heat resistance RFIN:
R
JA
TJA = 39 x PD
R
JC
+R
FIN = (R JA - R CA)
+R
FIN
.
(7)
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
13
STA6940M
Brushed DC Motor Driver IC With PWM Control
To extrapolate the junction temperature, TJ , 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 TCA . 5. Refer to figure 15 and locate the value found in step 4 on the TCA trace. 6. Determine the corresponding power dissipation, PD.
7. Substitute the values into the following equation:
TJ TCA + PD x R
JC .
(8)
Important notes: * Please ensure that the maximum rated junction temperature (150C) 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 = 80C maximum.
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
14
STA6940M
Brushed DC Motor Driver IC With PWM Control
Pin-out Diagram
2
4
6
8
10
12
14
16
18
Chamfer
1
3
5
7
9
11
13
15
17
(Top View)
Terminal List Table Number
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Symbol
VBB OA Sense1 IN1 IN2 VDD PWM_REF OCP_REF GND Diag CP2 CP1 CP Sense2 OB VBB
Function
Main supply input (motor supply) Motor terminal A Motor current sensing Control mode setting (please see truth table) Logic supply Constant-current setting Overcurrent setting Ground PWM diagnostic and OCP output Connection for charge pump Motor overcurrent sensing Motor terminal B Main supply input (motor supply)
*The VBB terminals, 1 and 18, are internally connected.
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
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 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 1.27 0.5 A 2.54 0.5 A
Branding Area
2X1.5 0.5
1
3
5
7
9
11
13
15
17
2
4
6
8
10
12
14
16
18
A B
Measured at pin tips Measured at case base
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.
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
16
STA6940M
Brushed DC Motor Driver IC With PWM Control
WARNING -- These devices are designed to be operated at lethal voltages and energy levels. Circuit designs that embody these components must conform with applicable safety requirements. Precautions must be taken to prevent accidental contact with power-line potentials. Do not connect grounded test equipment. The use of an isolation transformer is recommended during circuit development and breadboarding.
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 (5C to 35C) 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
indicated below: Type G746 YG6260 SC102 Soldering * When soldering the products, please be sure to minimize the working time, within the following limits: 2605C 10 s 3505C 3s Suppliers Shin-Etsu Chemical Co., Ltd. Momentive Performance Materials, Inc. Dow Corning Toray Silicone Co., Ltd.
*
Soldering iron should be at a distance of at least 1.5 mm from the body of the products When handling the products, operator must be grounded. Grounded wrist straps worn should have at least 1 M 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.
Electrostatic Discharge *
* * *
*
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
17
STA6940M
Brushed DC Motor Driver IC With PWM Control
The products described herein are manufactured in Japan by Sanken Electric Co., Ltd. for sale by Allegro MicroSystems, Inc. Sanken and Allegro reserve the right to make, from time to time, such departures from the detail specifications as may be required to permit improvements in the performance, reliability, or manufacturability of its products. Therefore, the user is cautioned to verify that the information in this publication is current before placing any order. When using the products described herein, the applicability and suitability of such products for the intended purpose shall be reviewed at the users responsibility. 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 society due to device failure or malfunction. Sanken products listed in this publication are designed and intended for use as components in general-purpose electronic equipment or apparatus (home appliances, office equipment, telecommunication equipment, measuring equipment, etc.). Their use in any application requiring radiation hardness assurance (e.g., aerospace equipment) is not supported. When considering the use of Sanken products in applications where higher reliability is required (transportation equipment and its control systems or equipment, fire- or burglar-alarm systems, various safety devices, etc.), contact a company sales representative to discuss and obtain written confirmation of your specifications. The use of Sanken products without the written consent of Sanken in applications where extremely high reliability is required (aerospace equipment, nuclear power-control stations, life-support systems, etc.) is strictly prohibited. The information included herein is believed to be accurate and reliable. Application and operation examples described in this publication are given for reference only and Sanken and Allegro assume no responsibility for any infringement of industrial property rights, intellectual property rights, or any other rights of Sanken or Allegro or any third party that may result from its use. Anti radioactive ray design is not considered for the products listed herein.
Copyright (c) 2009 Allegro MicroSystems, Inc.
This datasheet is based on Sanken application note
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
18
STA6940M
Brushed DC Motor Driver IC With PWM Control
Worldwide Contacts
Asia-Pacific China Sanken Electric Hong Kong Co., Ltd.
Suite 1026, Ocean Centre, Canton Road Tsimshatsui, Kowloon, Hong Kong Tel: 852-2735-5262, Fax: 852-2735-5494
Singapore Sanken Electric Singapore Pte. Ltd.
150 Beach Road, #14-03 The Gateway West Singapore 189720 Tel: 65-6291-4755, Fax: 65-6297-1744
Sanken Electric (Shanghai) Co., Ltd.
Room 3202, Maxdo Centre, Xingyi Road 8 Changning District, Shanghai, China Tel: 86-21-5208-1177, Fax: 86-21-5208-1757
Europe Sanken Power Systems (UK) Limited
Pencoed Technology Park Pencoed, Bridgend CF35 5HY, United Kingdom Tel: 44-1656-869-100, Fax: 44-1656-869-162
Taiwan Sanken Electric Co., Ltd.
Room 1801, 18th Floor, 88 Jung Shiau East Road Sec. 2, Taipei 100, Taiwan R.O.C. Tel: 886-2-2356-8161, Fax: 886-2-2356-8261
Japan Sanken Electric Co., Ltd. Overseas Sales Headquarters
Metropolitan Plaza Building, 1-11-1 Nishi-Ikebukuro Toshima-ku, Tokyo 171-0021, Japan Tel: 81-3-3986-6164, Fax: 81-3-3986-8637
North America United States Allegro MicroSystems, Inc.
115 Northeast Cutoff Worcester, Massachusetts 01606, U.S.A. Tel: 1-508-853-5000, Fax: 1-508-853-7895
Korea Sanken Electric Korea Co., Ltd.
Mirae Asset Life Building, 6F 168 Kongduk-dong, Mapo-ku Seoul 121-705, Korea Tel: 82-2-714-3700, Fax: 82-2-3272-2145
Allegro MicroSystems, Inc.
14 Hughes Street, Suite B105 Irvine, California 92618, U.S.A. Tel: 1-949-460-2003, Fax: 1-949-460-7837
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
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