Allegro A3952KEB, A3952KB, A3952SW, A3952SLB, A3952SEB Datasheet

...

Data Sheet

29319.1*

FULL-BRIDGE PWM MOTOR DRIVER

Designed for bidirectional pulse-width modulated current control of inductive loads, the A3952S– is capable of continuous output currents to ±2 A and operating voltages to 50 V. Internal fixed off-time PWM current-control circuitry can be used to regulate the maximum load current to a desired value. The peak load current limit is set by the user’s selection of an input reference voltage and external sensing resistor. The fixed OFF-time pulse duration is set by a user-selected external RC timing network. Internal circuit protection includes thermal shutdown with hysteresis, transient suppression diodes, and crossovercurrent protection. Special power-up sequencing is not required.

With the ENABLE input held low, the PHASE input controls load current polarity by selecting the appropriate source and sink driver pair. The MODE input determines whether the PWM current-control circuitry operates in a slow current-decay mode (only the selected sink driver switching) or in a fast current-decay mode (selected source and sink switching). A user-selectable blanking window prevents false triggering of the PWM current control circuitry. With the ENABLE input held high, all output drivers are disabled. A sleep mode is provided to reduce power consumption when inactive.

When a logic low is applied to the BRAKE input, the braking function is enabled. This overrides ENABLE and PHASE to turn OFF both source drivers and turn ON both sink drivers. The brake function can be safely used to dynamically brake brush dc motors.

The A3952S– is supplied in a choice of four power packages. In all package styles, the batwing/power tab is at ground potential and needs no isolation. These devices are also available for operation from -40°C to +125°C. To order, change the suffix from 'S–' to 'K–'.

FEATURES

■ ±2 A Continuous Output Current Rating

■ 50 V Output Voltage Rating

■ Internal PWM Current Control

■ Fast and Slow Current-Decay Modes

■ Sleep (Low Current Consumption) Mode

■ Internal Transient Suppression Diodes

■ Under-Voltage Lockout

■ Internal Thermal Shutdown Circuitry

■ Crossover-Current Protection

Always order by complete part number:

Part Number Package R

θJA

θJT

A3952SB 16-Pin DIP 43°C/W 6.0°C/W A3952SEB 28-Lead PLCC 42°C/W 6.0°C/W A3952SLB 16-Lead SOIC 67°C/W 6.0°C/W A3952SW 12-Pin Power-Tab SIP 36°C/W 2.0°C/W

A3952SB

Note that the A3952SB (DIP) and the A3952SLB (SOIC) are electrically identical and share a

common terminal number assignment.

ABSOLUTE MAXIMUM RATINGS

Load Supply Voltage, V

.................. 50 V

Output Current, I

OUT

≤ 20 µs).................................. ±3.5 A

(Continuous) ...............................

±2.0 A

Logic Supply Voltage, V

................. 7.0 V

Logic Input Voltage Range,

....................... -0.3 V to VCC + 0.3 V

Sense Voltage, V

SENSE

...................... 1.5 V

Reference Voltage, V

REF

.................... 15 V

Package Power Dissipation,

....................................... See Graph

Operating Temperature Range,

............................... –20°C to +85°C

Junction Temperature, T

............. +150°C*

Storage Temperature Range,

............................. –55°C to +150°C

Output current rating may be limited by duty cycle, ambient temperature, heat sinking and/or forced cooling. Under any set of conditions, do not exceed the specified current rating or a junction temperature of +150°C.

* Fault conditions that produce excessive junction temperature will activate device thermal shutdown circuitry. These conditions can be tolerated but should be avoided.

3952

MODE

GROUND

LOGIC

SUPPLY

PHASE

GROUND

SENSE

LOAD SUPPLY

Dwg. PP-056

BRAKE

REF

LOAD SUPPLY

OUT

LOGIC

ENABLE

3952

FULL-BRIDGE PWM MOTOR DRIVER

115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000

LOGIC

SUPPLY

LOAD

SUPPLY

PHASE

EMITTERS

UVLO

& TSD

Dwg. FP-036

MODE

REF

OUT

ENABLE

SENSE

–

BRAKE

INPUT LOGIC

GROUND

R S

1.5 V

PWM LATCH

+ –

BLANKING

SLEEP & STANDBY MODES

'EB' ONLY

'B', 'LB', & 'W' PACKAGES

FUNCTIONAL BLOCK DIAGRAM

TRUTH TABLE

BRAKE ENABLE PHASE MODE OUT

OUTBDESCRIPTION

H H X H Z Z Sleep Mode H H X L Z Z Standby, Note 1 H L H H H L Forward,

Fast-Decay Mode

H L H L H L Forward,

Slow-Decay Mode

H L L H L H Reverse,

Fast-Decay Mode

H L L L L H Reverse,

Slow-Decay Mode

L X X H L L Brake,

Fast-Decay Mode

L X X L L L Brake, No Current

Control, Note 2

X = Irrelevant Z = High Impedance (source and sink both OFF) NOTES: 1. Includes active pull-offs for power outputs.

2. Includes internal default V

sense

level for over-current protection.

50 75 100 125 150

TEMPERATURE IN °C

Dwg. GP-007-1A

ALLOWABLE PACKAGE POWER DISSIPATION IN WATTS

'W' TAB

'B' , 'EB', & 'LB' TAB

'W' AMBIENT

'B' & 'EB' AMBIENT

'LB' AMBIENT

3952

FULL-BRIDGE PWM MOTOR DRIVER

A3952SEB A3952SW

ELECTRICAL CHARACTERISTICS at T

= +25°C, V

= 50 V, VCC = 5.0 V, V

BRAKE

= 2.0 V,

SENSE

= 0 V, RC = 20 kΩ/1000 pF to Ground (unless noted otherwise).

Limits Characteristic Symbol Test Conditions Min. Typ. Max. Units Output Drivers

Load Supply Voltage Range V

Operating, I

OUT

= ±2.0 A, L = 3 mH V

– 50 V

Output Leakage Current I

CEX

OUT

= V

– <1.0 50 µA

OUT

= 0 V – <-1.0 -50 µA

Output Saturation Voltage V

CE(SAT)

Source Driver, I

OUT

= -0.5 A – 0.9 1.2 V

Source Driver, I

OUT

= -1.0 A – 1.0 1.4 V

Source Driver, I

OUT

= -2.0 A – 1.2 1.8 V

Sink Driver, I

OUT

= +0.5 A – 0.9 1.2 V

Sink Driver, I

OUT

= +1.0 A – 1.0 1.4 V

Sink Driver, I

OUT

= +2.0 A – 1.3 1.8 V

Clamp Diode Forward Voltage V

IF = 0.5 A – 1.0 1.4 V

(Source or Sink) IF = 1.0 A – 1.1 1.6 V

IF = 2.0 A – 1.4 2.0 V

Load Supply Current I

BB(ON)

ENABLE

= 0.8 V – 2.9 6.0 mA

(No Load) I

BB(OFF)

ENABLE

= 2.0 V, V

MODE

= 0.8 V – 3.1 6.5 mA

BRAKE

= 0.8 V – 3.1 6.5 mA

BB(SLEEP)

ENABLE

= V

MODE

= 2.0 V – <1.0 50 µA

12345 678 9101112

GROUND

Dwg. PP-058

MODE

LOGIC

SUPPLY

PHASE

SENSE

REF

LOAD

SUPPLY

OUT

ENABLE

LOGIC

BRAKE

GROUND

Dwg. PP-057

NOCONNECTION

EMITTERS

LOAD

SUPPLY

REF

LOGIC

BRAKE

LOGIC

SUPPLY

PHASE

ENABLE

MODE

SENSE

LOAD

SUPPLY

OUT

Continued next page …

3952

FULL-BRIDGE PWM MOTOR DRIVER

115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000

Control Logic

Logic Supply Voltage Range V

Operating 4.5 5.0 5.5 V

Logic Input Voltage V

IN(1)

2.0 ––V

IN(0)

––0.8 V

Logic Input Current I

IN(1)

VIN = 2.0 V – <1.0 20 µA

IN(0)

VIN = 0.8 V – <-2.0 -200 µA

Reference Voltage Range V

REF

Operating 0 – 15 V

Reference Input Current I

REF

= 2.0 V 25 40 55 µA

Reference Voltage Divider Ratio – V

REF

= 15 V 9.5 10.0 10.5 –

Comparator Input Offset Voltage V

REF

= 0 V – ±1.0 ±10 mV

PWM RC Fixed OFF Time t

off

CT = 1000 pF, RT = 20 kΩ 18 20 22 µs

PWM Minimum ON Time t

on(min)

CT = 820 pF, RT ≥ 12 kΩ – 1.7 3.0 µs CT = 1200 pF, RT ≥ 12 kΩ – 2.5 3.8 µs

Propagation Delay Time t

OUT

= ±2.0 A, 50% EIN to 90% E

OUT

Transition: ENABLE ON to Source ON – 2.9 – µs ENABLE OFF to Source OFF – 0.7 – µs ENABLE ON to Sink ON – 2.4 – µs ENABLE OFF to Sink OFF – 0.7 – µs PHASE Change to Source ON – 2.9 – µs PHASE Change to Source OFF – 0.7 – µs PHASE Change to Sink ON – 2.4 – µs PHASE Change to Sink OFF – 0.7 – µs

pd(pwm)

Comparator Trip to Sink OFF – 0.8 1.5 µs

Thermal Shutdown Temperature T

– 165 – °C

Thermal Shutdown Hysteresis ∆T

– 15 – °C

UVLO Disable Threshold V

CC(UVLO)

3.15 3.50 3.85 V

UVLO Hysteresis ∆V

CC(UVLO)

300 400 500 mV

Logic Supply Current I

CC(ON)

ENABLE

= 0.8 V, V

BRAKE

= 2.0 V – 20 30 mA

(No Load) I

CC(OFF)

ENABLE

= 2.0 V, V

MODE

= 0.8 V – 12 18 mA

CC(BRAKE)

BRAKE

= 0.8 V – 26 40 mA

CC(SLEEP)

ENABLE

= V

MODE

= V

BRAKE

= 2.0 V – 3.0 5.0 mA

NOTES: 1. Typical Data is for design information only.

2. Each driver is tested separately.

3. Negative current is defined as coming out of (sourcing) the specified device terminal.

Limits

Characteristic Symbol Test Conditions Min. Typ. Max. Units

3952

FULL-BRIDGE PWM MOTOR DRIVER

FUNCTIONAL DESCRIPTION

INTERNAL PWM CURRENT CONTROL DURING FORWARD AND REVERSE OPERATION

The A3952S– contains a fixed OFF-time pulse-width modulated (PWM) current-control circuit that can be used to limit the load current to a desired value. The value of the current limiting (I

TRIP

) is set by the selection of an external current sensing resistor (RS) and reference input voltage (V

REF

). The internal circuitry compares the voltage across the external sense resistor to one tenth the voltage on the REF input terminal, resulting in a function approximated by

TRIP

= V

REF

/(10RS).

In forward or reverse mode the current-control circuitry limits the load current. When the load current reaches I

TRIP

, the comparator resets a latch to turn OFF the selected sink driver (in the slow-decay mode) or selected sink and source driver pair (in the fast-decay mode). In slow-decay mode, the selected sink driver is disabled; the load inductance causes the current to recirculate through the source driver and flyback diode (see figure 1). In fastdecay mode, the selected sink and source driver pair are disabled; the load inductance causes the current to flow from ground to the load supply via the ground clamp and flyback diodes.

Figure 1 — Load-Current Paths

The user selects an external resistor (RT) and capacitor (CT) to determine the time period (t

off

= RTCT) during which the drivers remain disabled (see “RC Fixed OFF Time” below). At the end of the RTCT interval, the drivers are re-enabled allowing the load current to increase again. The PWM cycle repeats, maintaining the load current at the desired value (see figure 2).

ENABLE

MODE

LOAD

CURRENT

TRIP

Dwg. WP-015-1

Dwg. EP-006-2A

DRIVE CURRENT RECIRCULATION

(SLOW-DECAY MODE) RECIRCULATION

(FAST-DECAY MODE)

Figure 2 — Fast and Slow Current-Decay Waveforms

INTERNAL PWM CURRENT CONTROL DURING BRAKE MODE OPERATION

The brake circuit turns OFF both source drivers and turns ON both sink drivers. For dc motor applications, this has the effect of shorting the motor’s back-EMF voltage, resulting in current flow that brakes the motor dynamically. However, if the back-EMF voltage is large, and there is no PWM current limiting, then the load current can increase to a value that approaches a locked rotor condition. To limit the current, when the I

TRIP

level is reached, the PWM circuit disables the conducting sink driver. The energy stored in the motor’s inductance is then discharged into the load supply causing the motor current to decay.

As in the case of forward/reverse operation, the drivers

are re-enabled after a time given by t

off

= RTCT (see “RC Fixed OFF Time” below). Depending on the back-EMF voltage (proportional to the motor’s decreasing speed), the load current again may increase to I

TRIP

. If so, the PWM cycle will repeat, limiting the load current to the desired value.

Brake Operation - MODE Input High

During braking, when the MODE input is high, the

current limit can be approximated by

TRIP

= V

REF

/(10RS).

CAUTION: Because the kinetic energy stored in the motor and load inertia is being converted into current, which charges the VBB supply bulk capacitance (power supply output and decoupling capacitance), care must be taken to ensure the capacitance is sufficient to absorb the energy without exceeding the voltage rating of any devices connected to the motor supply.

+ 11 hidden pages