DRV8870 是一款刷式直流电机驱动器,适用于打印机、电器、工业设备以及其他小型机器。 两个逻辑输入控制 H 桥驱动器,该驱动器由四个 N 沟道金属氧化物半导体场效应晶体管 (MOSFET) 组成,能够以高达 3.6A 的峰值电流双向控制电机。 利用电流衰减模式,可通过对输入进行脉宽调制 (PWM) 来控制电机转速。 如果将两个输入均置为低电平,则电机驱动器将进入低功耗休眠模式。
DRV8870 具有集成电流调节功能,该功能基于模拟输入 VREF 以及 ISEN 引脚的电压(与流经外部感测电阻的电机电流成正比)。 该器件能够将电流限制在某一已知水平,这可显著降低系统功耗要求,并且无需大容量电容来维持稳定电压,尤其是在电机启动和停转时。
该器件针对故障和短路问题提供了全面保护,包括欠压锁定 (UVLO)、过流保护 (OCP) 和过热保护 (TSD)。 故障排除后,器件会自动恢复正常工作。
部件号 | 封装 | 封装尺寸(标称值) |
---|---|---|
DRV8870 | HSOP (8) | 4.90mm × 6.00mm |
空白
日期 | 修订版本 | 注释 |
---|---|---|
2015 年 8 月 | * | 首次发布。 |
PIN | TYPE | DESCRIPTION | ||
---|---|---|---|---|
NAME | NO. | |||
GND | 1 | PWR | Logic ground | Connect to board ground |
IN1 | 3 | I | Logic inputs | Controls the H-bridge output. Has internal pulldowns. (See Table 1.) |
IN2 | 2 | |||
ISEN | 7 | PWR | High-current ground path | If using current regulation, connect ISEN to a resistor (low-value, high-power-rating) to ground. If not using current regulation, connect ISEN directly to ground. |
OUT1 | 6 | O | H-bridge output | Connect directly to the motor or other inductive load. |
OUT2 | 8 | |||
PAD | — | — | Thermal pad | Connect to board ground. For good thermal dissipation, use large ground planes on multiple layers, and multiple nearby vias connecting those planes. |
VM | 5 | PWR | 6.5-V to 45-V power supply | Connect a 0.1-µF bypass capacitor to ground, as well as sufficient bulk capacitance, rated for the VM voltage. |
VREF | 4 | I | Analog input | Apply a voltage between 0.3 to 5 V. For information on current regulation, see the Current Regulation section. |
MIN | MAX | UNIT | |
---|---|---|---|
Power supply voltage (VM) | –0.3 | 50 | V |
Power supply voltage ramp rate (VM) | 0 | 2 | V/µs |
Logic input voltage (IN1, IN2) | –0.3 | 7 | V |
Reference input pin voltage (VREF) | –0.3 | 6 | V |
Continuous phase node pin voltage (OUT1, OUT2) | –0.7 | VM + 0.7 | V |
Current sense input pin voltage (ISEN) (2) | –0.5 | 1 | V |
Operating junction temperature, TJ | –40 | 150 | °C |
Storage temperature, Tstg | –65 | 150 | °C |
VALUE | UNIT | |||
---|---|---|---|---|
V(ESD) | Electrostatic discharge | Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001 (1) | ±6000 | V |
Charged-device model (CDM), per JEDEC specification JESD22-C101 (2) | ±750 |
MIN | NOM | MAX | UNIT | ||
---|---|---|---|---|---|
VM | Power supply voltage range | 6.5 | 45 | V | |
VREF | VREF input voltage range | 0.3 (1) | 5 | V | |
VI | Logic input voltage range (IN1, IN2) | 0 | 5.5 | V | |
fPWM | Logic input PWM frequency (IN1, IN2) | 0 | 100 | kHz | |
Ipeak | Peak output current (2) | 0 | 3.6 | A | |
TA | Operating ambient temperature (2) | –40 | 125 | °C |
THERMAL METRIC (1) | DRV8870 | UNIT | |
---|---|---|---|
DDA (HSOP) | |||
8 PINS | |||
RθJA | Junction-to-ambient thermal resistance | 41.1 | °C/W |
RθJC(top) | Junction-to-case (top) thermal resistance | 53.1 | °C/W |
RθJB | Junction-to-board thermal resistance | 23.1 | °C/W |
ψJT | Junction-to-top characterization parameter | 8.2 | °C/W |
ψJB | Junction-to-board characterization parameter | 23 | °C/W |
RθJC(bot) | Junction-to-case (bottom) thermal resistance | 2.7 | °C/W |
PARAMETER | TEST CONDITIONS | MIN | TYP | MAX | UNIT | |
---|---|---|---|---|---|---|
POWER SUPPLY (VM) | ||||||
VM | VM operating voltage | 6.5 | 45 | V | ||
IVM | VM operating supply current | VM = 12 V | 3 | 10 | mA | |
IVMSLEEP | VM sleep current | VM = 12 V | 10 | µA | ||
tON (1) | Turn-on time | VM > VUVLO with IN1 or IN2 high | 40 | 50 | µs | |
LOGIC-LEVEL INPUTS (IN1, IN2) | ||||||
VIL | Input logic low voltage | 0.5 | V | |||
VIH | Input logic high voltage | 1.5 | V | |||
VHYS | Input logic hysteresis | 0.5 | V | |||
IIL | Input logic low current | VIN = 0 V | -1 | 1 | μA | |
IIH | Input logic high current | VIN = 3.3 V | 33 | 100 | μA | |
RPD | Pulldown resistance | to GND | 100 | kΩ | ||
tPD | Propagation delay | INx to OUTx change (see Figure 6) | 0.7 | 1 | μs | |
tsleep | Time to sleep | Inputs low to sleep | 1 | 1.5 | ms | |
MOTOR DRIVER OUTPUTS (OUT1, OUT2) | ||||||
RDS(ON) | High-side FET on resistance | VM = 24 V, I = 1 A, TA = 25°C | 307 | 360 | mΩ | |
RDS(ON) | Low-side FET on resistance | VM = 24 V, I = 1 A, TA = 25°C | 258 | 320 | mΩ | |
tDEAD | Output dead time | 220 | ns | |||
Vd | Body diode forward voltage | IOUT = 1 A | 0.8 | 1 | V | |
CURRENT REGULATION | ||||||
AV | ISEN gain | VREF = 2.5 V | 9.4 | 10 | 10.4 | V/V |
tOFF | PWM off-time | 25 | µs | |||
tBLANK | PWM blanking time | 2 | µs | |||
PROTECTION CIRCUITS | ||||||
VUVLO | VM undervoltage lockout | VM falls until UVLO triggers | 6.1 | 6.4 | V | |
VM rises until operation recovers | 6.3 | 6.5 | ||||
VUV,HYS | VM undervoltage hysteresis | Rising to falling threshold | 100 | 180 | mV | |
IOCP | Overcurrent protection trip level | 3.7 | 4.5 | 6.4 | A | |
tOCP | Overcurrent deglitch time | 1.5 | μs | |||
tRETRY | Overcurrent retry time | 3 | ms | |||
TSD | Thermal shutdown temperature | 150 | 175 | °C | ||
THYS | Thermal shutdown hysteresis | 40 | °C |
The DRV8870 is an optimized 8-pin device for driving brushed DC motors with 6.5 to 45 V and up to 3.6-A peak current. The integrated current regulation restricts motor current to a predefined maximum. Two logic inputs control the H-bridge driver, which consists of four N-channel MOSFETs that have a typical Rds(on) of 565 mΩ (including one high-side and one low-side FET). A single power input, VM, serves as both device power and the motor winding bias voltage. The integrated charge pump of the device boosts VM internally and fully enhances the high-side FETs. Motor speed can be controlled with pulse-width modulation, at frequencies between 0 to 100 kHz. The device has an integrated sleep mode that is entered by bringing both inputs low. An assortment of protection features prevent the device from being damaged if a system fault occurs.
The DRV8870 output consists of four N-channel MOSFETs that are designed to drive high current. They are controlled by the two logic inputs IN1 and IN2, according to Table 1.
IN1 | IN2 | OUT1 | OUT2 | DESCRIPTION |
---|---|---|---|---|
0 | 0 | High-Z | High-Z | Coast; H-bridge disabled to High-Z (sleep entered after 1 ms) |
0 | 1 | L | H | Reverse (Current OUT2 → OUT1) |
1 | 0 | H | L | Forward (Current OUT1 → OUT2) |
1 | 1 | L | L | Brake; low-side slow decay |
The inputs can be set to static voltages for 100% duty cycle drive, or they can be pulse-width modulated (PWM) for variable motor speed. When using PWM, it typically works best to switch between driving and braking. For example, to drive a motor forward with 50% of its max RPM, IN1 = 1 and IN2 = 0 during the driving period, and IN1 = 1 and IN2 = 1 during the other period. Alternatively, the coast mode (IN1 = 0, IN2 = 0) for fast current decay is also available. The input pins can be powered before VM is applied.
When IN1 and IN2 are both low for time tSLEEP (typically 1 ms), the DRV8870 enters a low-power sleep mode, where the outputs remain High-Z and the device uses IVMSLEEP (microamps) of current. If the device is powered up while both inputs are low, sleep mode is immediately entered. After IN1 or IN2 are high for at least 5 µs, the device will be operational 50 µs (tON) later.
The DRV8870 limits the output current based on the analog input VREF and the resistance of an external sense resistor on pin ISEN, according to this equation:
For example, if VREF = 3.3 V and a RISEN = 0.15 Ω, the DRV8870 will limit motor current to 2.2 A no matter how much load torque is applied. For guidelines on selecting a sense resistor, see Sense Resistor.
When ITRIP has been reached, the device enforces slow current decay by enabling both low-side FETs, and it does this for time tOFF (typically 25 µs).
After tOFF has elapsed, the output is re-enabled according to the two inputs INx. The drive time (tDRIVE) until reaching another ITRIP event heavily depends on the VM voltage, the motor’s back-EMF, and the motor’s inductance.
When an output changes from driving high to driving low, or driving low to driving high, dead time is automatically inserted to prevent shoot-through. tDEAD is the time in the middle when the output is High-Z. If the output pin is measured during tDEAD, the voltage will depend on the direction of current. If current is leaving the pin, the voltage will be a diode drop below ground. If current is entering the pin, the voltage will be a diode drop above VM. This diode is the body diode of the high-side or low-side FET.
The DRV8870 is fully protected against VM undervoltage, overcurrent, and overtemperature events.
If at any time the voltage on the VM pin falls below the undervoltage lockout threshold voltage, all FETs in the H-bridge will be disabled. Operation will resume when VM rises above the UVLO threshold.
If the output current exceeds the OCP threshold IOCP for longer than tOCP, all FETs in the H-bridge are disabled for a duration of tRETRY. After that, the H-bridge will be re-enabled according to the state of the INx pins. If the overcurrent fault is still present, the cycle repeats; otherwise normal device operation resumes.
If the die temperature exceeds safe limits, all FETs in the H-bridge will be disabled. After the die temperature has fallen to a safe level, operation automatically resumes.
FAULT | CONDITION | H-BRIDGE BECOMES | RECOVERY |
---|---|---|---|
VM undervoltage lockout (UVLO) | VM < VUVLO | Disabled | VM > VUVLO |
Overcurrent (OCP) | IOUT > IOCP | Disabled | tRETRY |
Thermal Shutdown (TSD) | TJ > 150°C | Disabled | TJ < TSD – THYS |
The DRV8870 can be used in multiple ways to drive a brushed DC motor.
This scheme uses all of the device’s capabilities. ITRIP is set above the normal operating current, and high enough to achieve an adequate spin-up time, but low enough to constrain current to a desired level. Motor speed is controlled by the duty cycle of one of the inputs, while the other input is static. Brake/slow decay is typically used during the off-time.
If current regulation is not needed, pin ISEN should be directly connected to the PCB ground plane. VREF must still be 0.3 to 5 V, and larger voltages provide greater noise margin. This mode provides the highest possible peak current: up to 3.6 A for a few hundred milliseconds (depending on PCB characteristics and the ambient temperature). If current exceeds 3.6 A, the device might reach overcurrent protection (OCP) or overtemperature shutdown (TSD). If that happens, the device disables and protects itself for about 3 ms (tRETRY) and then resumes normal operation.
IN1 and IN2 can be set high and low for 100% duty cycle drive, and ITRIP can be used to control the motor’s current, speed, and torque capability.
In some systems it is desirable to vary VM as a means of changing motor speed. See Motor Voltage for more information.
NOTE
Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.
The DRV8870 is typically used to drive one brushed DC motor.
Table 3 lists the design parameters.
DESIGN PARAMETER | REFERENCE | EXAMPLE VALUE |
---|---|---|
Motor voltage | VM | 24 V |
Motor RMS current | IRMS | 0.8 A |
Motor startup current | ISTART | 2 A |
Motor current trip point | ITRIP | 2.2 A |
VREF voltage | VREF | 3.3 V |
Sense resistance | RISEN | 0.15 Ω |
PWM frequency | fPWM | 5 kHz |
The motor voltage to use will depend on the ratings of the motor selected and the desired RPM. A higher voltage spins a brushed DC motor faster with the same PWM duty cycle applied to the power FETs. A higher voltage also increases the rate of current change through the inductive motor windings.
The current path is through the high-side sourcing DMOS power driver, motor winding, and low-side sinking DMOS power driver. Power dissipation losses in one source and sink DMOS power driver are shown in the following equation.
The DRV8870 has been measured to be capable of 2-A RMS current at 25°C on standard FR-4 PCBs. The max RMS current will vary based on PCB design and the ambient temperature.
For optimal performance, it is important for the sense resistor to be:
The power dissipated by the sense resistor equals IRMS2 × R. For example, if peak motor current is 3 A, RMS motor current is 1.5 A, and a 0.2-Ω sense resistor is used, the resistor will dissipate 1.5 A2 × 0.2 Ω = 0.45 W. The power quickly increases with higher current levels.
Resistors typically have a rated power within some ambient temperature range, along with a derated power curve for high ambient temperatures. When a PCB is shared with other components generating heat, the system designer should add margin. It is always best to measure the actual sense resistor temperature in a final system.
Because power resistors are larger and more expensive than standard resistors, it is common practice to use multiple standard resistors in parallel, between the sense node and ground. This distributes the current and heat dissipation.
Having appropriate local bulk capacitance is an important factor in motor drive system design. It is generally beneficial to have more bulk capacitance, while the disadvantages are increased cost and physical size.
The amount of local capacitance needed depends on a variety of factors, including:
The inductance between the power supply and motor drive system will limit the rate current can change from the power supply. If the local bulk capacitance is too small, the system will respond to excessive current demands or dumps from the motor with a change in voltage. When adequate bulk capacitance is used, the motor voltage remains stable and high current can be quickly supplied.
The data sheet generally provides a recommended value, but system-level testing is required to determine the appropriate sized bulk capacitor.
The voltage rating for bulk capacitors should be higher than the operating voltage, to provide margin for cases when the motor transfers energy to the supply.
The bulk capacitor should be placed to minimize the distance of the high-current path through the motor driver device. The connecting metal trace widths should be as wide as possible, and numerous vias should be used when connecting PCB layers. These practices minimize inductance and allow the bulk capacitor to deliver high current.
Small-value capacitors should be ceramic, and placed closely to device pins.
The high-current device outputs should use wide metal traces.
The device thermal pad should be soldered to the PCB top-layer ground plane. Multiple vias should be used to connect to a large bottom-layer ground plane. The use of large metal planes and multiple vias help dissipate the I² x RDS(on) heat that is generated in the device.
Recommended layout and component placement is shown in the following diagram.
The DRV8870 device has thermal shutdown (TSD) as described in the Thermal Shutdown (TSD) section. If the die temperature exceeds approximately 175°C, the device is disabled until the temperature drops below the temperature hysteresis level.
Any tendency of the device to enter TSD is an indication of either excessive power dissipation, insufficient heatsinking, or too high of an ambient temperature.
Power dissipation in the DRV8870 device is dominated by the power dissipated in the output FET resistance, RDS(on). Use the equation in the Drive Current section to calculate the estimated average power dissipation when driving a load.
Note that at startup, the current is much higher than normal running current; this peak current and its duration must be also be considered.
The maximum amount of power that can be dissipated in the device is dependent on ambient temperature and heatsinking.
NOTE
RDS(on) increases with temperature, so as the device heats, the power dissipation increases. This fact must be taken into consideration when sizing the heatsink.
The power dissipation of the DRV8870 is a function of RMS motor current and the FET resistance (RDS(ON)) of each output.
For this example, the ambient temperature is 58°C, and the junction temperature reaches 80°C. At 58°C, the sum of RDS(ON) is about 0.72 Ω. With an example motor current of 0.8 A, the dissipated power in the form of heat will be 0.8 A2 × 0.72 Ω = 0.46 W.
The temperature that the DRV8870 reaches will depend on the thermal resistance to the air and PCB. It is important to solder the device PowerPAD to the PCB ground plane, with vias to the top and bottom board layers, in order dissipate heat into the PCB and reduce the device temperature. In the example used here, the DRV8870 had an effective thermal resistance RθJA of 48°C/W, and:
The PowerPAD package uses an exposed pad to remove heat from the device. For proper operation, this pad must be thermally connected to copper on the PCB to dissipate heat. On a multi-layer PCB with a ground plane, this connection can be accomplished by adding a number of vias to connect the thermal pad to the ground plane.
On PCBs without internal planes, a copper area can be added on either side of the PCB to dissipate heat. If the copper area is on the opposite side of the PCB from the device, thermal vias are used to transfer the heat between top and bottom layers.
For details about how to design the PCB, refer to the TI application report, PowerPAD™ Thermally Enhanced Package (SLMA002), and the TI application brief, PowerPAD Made Easy™ (SLMA004), available at www.ti.com. In general, the more copper area that can be provided, the more power can be dissipated.
The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of Use.
PowerPAD, E2E are trademarks of Texas Instruments.
All other trademarks are the property of their respective owners.
这些装置包含有限的内置 ESD 保护。 存储或装卸时,应将导线一起截短或将装置放置于导电泡棉中,以防止 MOS 门极遭受静电损伤。
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