Features

Four 1/2 H bridge DC motors drivers

-The can drive four solenoid valves, two DC motors, one -step motor or other load

- All independent half -bridge control

- Low MOSFET drive resistance

24 V, the maximum driving current at 25 ° C is 2.5 A [123 123 ]

Floating input buffer allows the double (double pole) power supply (up to ± 30 V)

built-in 3.3-V, 10 ma LDO regulator

] Industrial Standard IN/IN Digital Control Interface

8-V to 60-V working power supply voltage range

]

thermal enhancement surface -installed component

Application

Textile machinery

123] Game machine

Factory automation

Robotics

DRV8844 [DRV8844 [ 123] Provide four 1/2 H bridge drives that can be controlled separately. It can be used to drive two DC motors, one step motor, four thread pipes, or other loads. The power of each Mosh-1 channel consists of Mosh-1 channel driver configuration configured in the Mosh-1 channel.

DRV8844 can provide up to 2.5 A peak or 1.75 A RMS output current for each H bridge (proper PCB heat dissipation at 24 V and 25 ° C).

Provide an independent input to control each 1/2 H bridge independently. In order to allow the use of separation power to operate, logical input and fault output are referring to a separate floating ground pins.

Provide internal shutdown functions of over -current protection, short -circuit protection, under pressure locking and overheating.

DRV8844 uses a 28 -pin HTSSOP package with PowerPad #8482; (Environmental Protection: Rohs and NO SB/BR).

Equipment information

(1), please refer to the appointment appendix at the end of the data table.

Simplified schematic diagram

Typical features

Detailed description

Overview

DRV8844 integrated four independent 2.5 half -hour bridge, protection circuit, dormant mode and fault report. Its single power supply supports 8 to 60 volts, making it very suitable for motor -driven applications, including brushing DC, stepping on motor and threading tube.

Function box diagram

Feature description

output level

DRV8844 contains four n -channel MOSFET 1 1 1 /2 H bridge driver. The frame diagram of the output circuit is shown in Figure 5.

The output pin is driven between VM and VNEG. For single -power applications, VNEG is usually grounded. For dual -power applications, VNEG is usually negative voltage.

Please note that there are multiple VM motor power sources. All VM pins must be connected to the motor voltage.

Logic input

Logic input and NFAULT output reference LGND pins. The pin will be connected to the logic (for example, a microcontroller) of the logical signal source. This makes the voltage of LGND different from VNEG; for example, designers can drive bipolar power by driving VM and VNEG to drive the load and connect LGND to 0V (ground).

Bridge control

Inx input pin directly controls the status (high or low) of the outx output; ENX input pins to enable or disable the OUTX driver. Table 1 shows logic.

Input can also be used for PWM control, for example, the speed of DC motor. When a PWM is controlled by PWM, when the driver current is interrupted, the sensing characteristics of the motor must continue to flow. This is called a re -cycle current. In order to process this re -cycle current, HBRIDGE can work in two different states, fast attenuation or slow attenuation. In the fast attenuation mode, the H bridge is disabled, and the recycling current flows over the body diode; in the slow attenuation mode, the motor winding is short -circuit.

For PWM, PWM signals using fast attenuation to ENX pins; for the use of slow attenuation, PWM signals are applied to INX pin. Table 2 is an example of using OUT1 and OUT2 as the H bridge driver DC motor:

Figure 6 shows the current path of different drivers and attenuation modes:

]

The oil supply pump

Because the output level uses the N groove FET, a grid drive voltage that is higher than the VM power supply is required to fully enhance the high side FET. DRV8844 integrates a charge pump circuit, which can generate voltage higher than the VM power supply.

The charge pump requires two outsideCapacitors can work. For detailed information about these capacitors (values, connections, etc.), please refer to the box diagram and pipe foot instructions.

When nsleep is low, the charging pump is closed.

Protective circuit

DRV8844 has sufficient protection to prevent pressure, over current and overheating events.

Overcurrent protection (OCP)

The analog current limit circuit on each FET is limited to the current by removing the grid driver. If the duration of the analog current exceeds OCP lithium dewaloming time, the channels that have undergone current will be disabled, and the NFAULT pin will be driven to a low level. The driver will keep closed until asserting to reset or turn off the VM power supply.

Over -current conditions on high -voltage and low -voltage side devices; that is, short -circuit, short -circuit of power supply, or short circuit of motor winding, will lead to over -current stop.

Hot shutdown (TSD)

If the mold temperature exceeds the safety limit, all FETs in the H bridge will be disabled, and the NFAULT pin will be driven to a low level. Once the mold temperature drops to the safe level, the operation will automatically restore.

IOU locking (UVLO)

If the voltage on the VM pin is lower than the voltage lock threshold voltage at any time, all outputs will be disabled, the internal logic will be reset, the NFAULT pin will pin It will be driven to a low level. When VM is higher than the UVLO threshold, the operation will be restored.

Equipment function mode

reset and reset operation

When low level driving, NRESET pin reset internal logic. It also disables the H bridge driver. When NRESET is active, all inputs will be ignored.

Driving NSLEEP low will enable the device to enter a low -power sleep state. In this state, the H bridge is disabled, the gate driver's charge pump stops, and all internal clock stops. In this state, all inputs are ignored until NSLEEP returns Inactive High. When returning from the sleep mode, the motor drive can be fully worked after a period of time (about 1 millisecond). Note that the internal drop -down resistance of NRESET and NSLEEP is about 100kΩ. These signals need to be driven to logic high levels for device operations.

V3P3out LDO regulator keep working in dormant mode.

Application and implementation

Note

The information in the following application chapters is not part of the TI component specification, TI does not guarantee its accuracy or integrity. TI's customers are responsible for determining the applicability of the component. Customers should verify and test their design implementation to confirm the system function.

Application information

DRV8844 can be used to drive a step motor, multiple DC motors or multiple other inductive loads.

The output can be parallel to increase the driving current. If the output is connected in the whole bridge configuration, any two outputs can be connected in parallel. If the configuration is configured with two independent semi -bridge, OUT1 and OUT2 must be paired, and OUT3 and OUT4 must be paired. This pairing is because the pins (SRC12) is the source of the low -end FET of OUT1 and OUT2, and the pin 9 (SRC34) is the source of the low -end FET of OUT3 and OUT4.

Optional sensor can be used to monitor current. If the sensor is used, the resistor is placed between the SRC12 or SRC34 pins and the VNEG pin.

Typical application

Design requirements

The true value table below describes how to control the arrangement in Figure 8.

Detailed design program motor voltage

The rated value of the selected motor and the required speed determine the designer should use what the designer should use Motor voltage. The higher voltage makes the rotation speed of the brushing motor faster, and the same pulse width modulation duty cycle is applied to the power field effect transistor. The higher voltage will also increase the current changes in the current through the inductive motor winding.

Application curve

Power Suggestion

ontophyllum capacitance

In the design of the motor drive system, it has a suitable partial part Volume capacitance is an important factor. Generally speaking, more volume capacitors are beneficial, but the disadvantage is increased cost and physical dimensions.

The capacity depends on various local factors, including:

the highest current required for the motor system

Ability

Positive inductance between the power supply and the motor system

Electrical type (there are brushing DC, brushless DC, step motor)

Electrical braking method

The inductance between the power supply and the motor drive system limits the rated current of the power supply Variety. If the local large -capacity capacitance is too small, the system responds to the large current requirements of the motor according to the voltage change or the reserves of the storage. When using sufficient large -capacity capacitors, the motor voltage remains stable and can quickly provide large current.

The data table usually provides a recommended value, but it is necessary to perform system -level tests to determine large -capacity capacitors with appropriate size.

The rated voltage of a large capacitor should be higher than the operating voltage, so that it can provide a lot of time when the motor transmits energy to the power supply.

Layout

Layout Guide

The placement of large -capacity capacitors should be reduced as much as possible to drive the distance from the large current path of the motor -driven device. The width of the metal trace line should be as wide as possible, and multiple excess perforated should be used when connecting the PCB layer. These methods minimize the inductance and allow large capacitor to transport high current.

Small capacitors should be ceramic and placed in a place where the device pin is very close.

The output of high -current equipment shall use wide metal traces.

The equipment hot pad should be welded on the floor floor floor of the PCB. Multiple pores should be used to connect to large bottom ground planes. Use large metal planes and multiple holes to help the I2 × RDS (ON) heat generated in the dissipation device.

layout example

Heat Precautions

DRV8844 has the heat shutdown (TSD) as described above. If the mold temperature exceeds about 150 ° C, the device will be disabled until the temperature drops to the safe level.

Any trend of the device entering TSD indicates that the power consumption is too large, insufficient heat dissipation, or the environmental temperature is too high.

Heating

Power board #8482; Packaging uses an exposed cushion to remove the heat of the device. In order to correctly operate, the pad must be connected to the copper heat on the PCB to dissipate heat. On the multi -layer PCB with the floor, this can be achieved by adding multiple holes to connect the hot pad to the horizon. On PCB without internal planes, you can add copper area to any side of the PCB to dissipate heat. If the copper zone is on the other side of the PCB, the thermal hole is used to convey the heat between the top and the bottom layer.

Generally speaking, the more copper area provided, the greater the consumption power.

Power consumption

The power consumption of DRV8844 is mainly controlled by the output FET resistance or RDS (on) consumption. The average power consumption of each H bridge at the time of DC motor can be roughly estimated by 1.

where:

p ON) is the resistance of each fET

IOUT is an RMS output current that is applied to each winding (1)

ouut equal to the average current of the DC motor. Note that under starting and fault conditions, the current is much higher than the normal operating current; these peak currents and its duration need to be considered. Factor 2 comes from such a fact: at any moment, two fETs are conducting woundsStream (a high -pressure side and a low -pressure side).

The total device loss is the power consumption of each of the two H bridges.

The maximum power consumed in the device depends on the ambient temperature and heat dissipation.

Note that RDS (on) increases as the temperature increases, so when the device is heated, the power consumption will increase.When determining the size of the heat sink, this must be considered.