Features

Single H bridge current control motor drive

8.2-v to 45-v working power supply voltage range

# 8226; 5 -bit current control allows up to 32 current levels

low MOSFET RDS (open), typical 0.65 (HS+LS)

#8226 The maximum driver current at 24 V is 5 A, TA 25 ° C

built -in 3.3V reference output

] thermal enhancement surface installation component

Protection function:

- Over -current protection (OCP)

- Internal shutdown of heat shutdown (TSD) (TSD)

-vm under pressure lock (UVLO)

-The fault status indicator pins (nfault)

Application

Printer

scanner

Office automation machine

Game console

Factory automation

123] Robotics

Instructions

DRV8840

provides an integrated motor driver solution for printers, scanners and other automated equipment applications. The device has an H bridge drive to drive a DC motor. Each output drive block consists of N -channel power MOSFET, configured to drive the full H bridge to drive the motor winding. DRV8840 can provide output currents up to 5 amp or 3.5 amp (proper heat dissipation at 24 V and 25 ° C).

A simple parallel digital control interface is compatible with industrial standard equipment. The attenuation mode can be programmed so that the electrical mechanism is allowed to develop or taxi when disabled.

Provide internal shutdown functions of overcurrent protection, short -circuit protection, low -voltage locking and ultra -temperature. DRV8840 uses a 28 -pin HTSSOP package with PowerPad #8482; (Environmental: Rohs and NO SB/BR).

Equipment information

(1), please refer to the appointment of the doctor's order content at the end of the data table.

Simplified schematic diagram

Typical features

Detailed instructions

Overview

DRV8840 is an integrated motor driver solution that is suitable for printers, scanners and other automated equipment applications. This device integrates a single NMOS H bridge, charge pump, current detection, current adjustment and device protection circuit. DRV8828 can supply power from 8.2V to 45V, and can provide continuous output current up to 5A.

A simple Phase/ENBL interface can easily connect to the external controller. The 5 -bit current control scheme allows up to 32 discrete current levels. The current adjustment method can be adjusted between slow attenuation and fast attenuation.

Integrated protection circuits allow equipment monitoring and protection of over -current, under pressure and overheating failures. These faults are reported through fault indicator pins (NFAULT). Integrate a low -power dormant mode, allowing the system to reduce power consumption when not driving the motor.

Function box diagram

Feature description

PWM motor drive

DRV8840 device contains a current control PWM circuit H bridge motor driver. The frame diagram of the motor control circuit is shown in Figure 5.

There are multiple VM, Isen, OUT, and VREF pin. All naming pipes must be connected together on PCB.

Bridge control

Phase input pins control the current direction of the current flow of the H bridge, thereby controlling the rotation direction of the DC motor. ENBL input pin enables the H bridge output when high -level activation, and can also be used for the PWM speed control of the motor. Note that when ENBL 0, the behavior of selecting a bridge connection in the state of the aggressive tube is allowed to choose slow attenuation (braking) or rapid attenuation (gliding). Table 1 shows logic.

Control the input of internal pull -off resistors with about 100 kΩ.

current adjustment

The maximum current of the motor winding is adjusted by a fixed frequency PWM current adjustment or current cut wave wave. When the H bridge is enabled, the current passes through the winding to rises on the velocity of the DC voltage and inductance of the winding. Once the current reaches the current chopping threshold, the bridge will disable the current until the next PWM cycle starts.

For DC motors, the current adjustment is used to limit the starting of the motor and the stall current. Speed control is usually executed by providing external PWM signals to ENBLX input pins.

If the current adjustment function is not required, it can be disabled by connecting the Isense pin directly to the ground and connecting the VREF pin to V3P3.

PWM cut wave currentThe comparator settings, the comparator will compare the voltage of the current detection resistor that is connected to the Isen pin. The reference voltage is input from the VREF pin and is zoomed in through 5 digits of DAC. The DAC allows the current to set the current to 0 to 100%in the order of a sine.

Full marking (100%) cut wave current is calculated in Formula 1.

Example:

If you use 0.25- sensor and VREFX pin to 2.5 V, the full marker (100% 100% ) The cutting current will be 2.5 V/(5 × 0.25 ) 2 a.

Five input pins (I0-I4) are used to shrink the current in the bridge into a percentage of the full volume current set by VREF input pins and sensing resistance settings. The internal drop-down resistance of the i0-I4 pins is about 100 kΩ. The function of sales is shown in Table 2.

Attenuation mode and braking

During the PWM current chopping process, the H bridge can drive the current through the motor winding until the PWM current cut threshold is reached Essence This shows case 1 in Figure 6. The displayed current direction indicates the status of Xenbl's pin.

Once the cutting current threshold is reached, the H bridge can work in two different states, fast attenuation or slow attenuation.

In the fast attenuation mode, once the PWM cutting current level is reached, the H bridge will reverse to allow the winding current reverse flow. When the winding current is close to zero, the bridge is banned to prevent any reverse current flow. The fast attenuation mode is shown in Figure 6 as the case 2.

Under the mode of slow attenuation mode, by enabling the two low -border effects crystal tube in the bridge, the winding current is re -circulated. This is shown in Figure 6 as Case 3.

DRV8840 device supports fast attenuation and slow attenuation mode. Slow or fast decay mode is selected from the state of the decaying tube-low logic selection slow decay, and the logic high sets the fast decay mode. The internal pull -up resistance of the decaying tube is about 130 kΩ, and the internal pull -down resistance is about 80 kΩ. If the pin is kept or unavailable, a mixed attenuation mode is set.

The decay mode will also affect the operation of the bridge when disabled (by being in a non -active state by making the ENBL pins). This item is applicable if enabled the PWM speed control for the input for the motor, or only for starting and stopping motor rotation.

If the attenuation pin is high (rapid attenuation), when the bridge is disabled, it will enter the fast attenuation mode until the current of the bridge reaches zero. Once the current is zero, the bridge will be disabled to prevent the direction of the motor. This allows the engine to slide to the stop position.

If the decay pins are low (slow decay),When ENBL fails, both low -side FETs will be opened. This basically shortens the electromotive motor, leading to the motor to operate and stops quickly. Even after the current reaches zero, the low -side effect transistor will still maintain a direction state.

Sweeding time

After the current is enabled in the H bridge, the voltage on the Xisen pins will be ignored before the current detection circuit is enabled. The hidden time is fixed to 3.75μs. Note that the hidden time also sets up the minimum connection time of PWM.

Protective circuit

DRV8840 equipment 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 simulation current limits the duration of the OCP time, all FETs in the H bridge will be disabled, and the NFAULT pin will be driven to a low level. The device will remain disabled until NRESET PIN is applied, or VM is removed and re -applied.

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. Note that over -current protection is not used for current detection circuits for PWM current control, and it has nothing to do with Isense resistance or VREF voltage.

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 pins is lower than the voltage of the underwriting lock at any time, all circuits in the device will be disabled, the internal logic will be heavy, and the internal logic will be heavy. Set. 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, the V3P3OUT regulator is disabled, 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.

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

DRV8840 device is used to control motor or step motor control. The boarding current adjustment allows the motor current by simple pins configuration.

Typical application

Design requirements

Table 3 shows the design parameters of the application.

Detail (RSense) Set. When there is a mobilization of DC electricity, there may be large inspirational surge because there is no anti -electromotive force and high braking torque. The current adjustment will limit the influx of current and prevent high current when starting.

Example: If the required chop current is 1.5 A: Set RSENSE 100 MΩ

#8226; VREF must be 0.75 v

Create a resistor network from V3P3OUT (3.3 v) to set VREF 0.75 v

Set R2 10 k , set R1 3 K

sensor resistor

In order to obtain the best performance, the sensor must be:

# 8226; Surface installation

Low inductance

The rated power is high enough

The power consumption of the resistor is equal to IRMS2 × R. For example, if the current of the average root motor is 1.5 A and the sensor is used with 200 m the resistor will consume 1.5 A2 × 0.2 0.3 W. As the current level increases, power increases rapidly.

The resistor usually has a rated power within certain ambient temperature range, and the reduction of power curve at high ambient temperature. When a PCB is shared with other heating elements, the balance should be increased. It is best to measure the actual sensing resistance temperature and power MOSFET in the final system, because they are usually the hottest components.

Because ofThe power resistor is larger and more expensive than the standard resistor, so multiple standard resistors are used in parallel between sensing nodes and grounding. This can allocate current and heat dissipation.

Application curve

Power suggestion

DRV8840 design is used to work under the input voltage power supply (VM) of 8.2 V to 45 V. Essence The absolute maximum rated value of the device is 47 V. A 0.1-μF ceramic capacitor with a rated value of VM must be placed at each VM pin, as close to DRV8840 as much as possible. In addition, VM must include a large capacitor.

Overall capacitance size

It is an important factor in the design of the motor drive system. Generally speaking, more volume capacitors are beneficial, but the disadvantage is increased cost and physical dimensions.

The required local power capacity depends on multiple factors, including:

the highest current required for the motor system.

capacitance and ability to provide current.

Parasitic inductance between the power supply and the motor system.

acceptable voltage ripples.

the type of motor (brush, brushless DC, step motor).

motor braking method.

The inductance between the power supply and the motor drive system will limit the change rate of power current. If the local large -capacity capacitance is too small, the system will respond to excessive current requirements, or uninstall from the motor as the voltage changes. 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 greater than the operating voltage in order to provide the maneuverability when the motor transmits energy to the power supply.

Layout

Layout Guide

Each VM terminal must use low ESR ceramic road capacitors bypass to GND, the recommended value is to be, the recommended value is to be, the recommended value is to be, the recommended value is to be, and the recommended value is to be. VM rated value is 0.1 μF. These capacitors should be placed near the VM pin as much as possible, and have a thick trace line or ground plane connection with the GND pins of the device.

VM pins must use large -capacity capacitors rated as VM to bypass the ground. This ingredient may be an electrolyte.

Low ESR ceramic capacitors must be placed between CP1 and CP2 pin. TI recommends VM's rated value of 0.1 μF. Try this part as close as possible.

Low ESR potteryPorcelain containers must be placed between VM and VCP pins. TI's recommended 16 V rated value is 0.47 μF. Try this part as close as possible. In addition, 1 MΩ is placed between VM and VCP.

Use a ceramic capacitor with a rated voltage of 6.3 V to bypass V3P3 to ground. The bypass capacitor is as close to the pin as much as possible.

The current detecting the resistor should be as close to the device pin as much as possible to minimize the traces of the traces between the pin and the resistor.

layout example

Heat Precautions

DRV8840 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.

Power consumption

The average power consumption of DRV8840 when running a DC motor can be roughly estimated: Formula 3.

where:

The resistance of each fet

IOUT is an RMS output current for each winding.

IOUT is equal to the average current of DC motors. 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 the winding current (a high -voltage side and a low -voltage side).

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.

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.