UC3717AN_技术文档

UC3717A

Stepper Motor Drive Circuit

FEATURES

DESCRIPTION

•

Full-Step, Half-Step and Micro-Step

Capability

The UC3717A is an improved version of the UC3717, used to switch

drive the current in one winding of a bipolar stepper motor. The

UC3717A has been modified to supply higher winding current, more

reliable thermal protection, and improved efficiency by providing inte-

grated bootstrap circuitry to lower recirculation saturation voltages.

The diagram shown below presents the building blocks of the

UC3717A. Included are an LS-TTL compatible logic input, a current

sensor, a monostable, a thermal shutdown network, and an H-bridge

output stage. The output stage features built-in fast recovery com-

mutating diodes and integrated bootstrap pull up. Two UC3717As

and a few external components form a complete control and drive

unit for LS-TTL or micro-processor controlled stepper motor systems.

•

Bipolar Output Current up to 1A

Wide Range of Motor Supply Voltage

10-46V

•

Low Saturation Voltage with Integrated

Bootstrap

Built-In Fast Recovery Commutating

Diodes

Current Levels Selected in Steps or Varied

Continuously

The UC3717A is characterized for operation over the temperature

range of 0°C to +70°C.

Thermal Protection with Soft Intervention

ABSOLUTE MAXIMUM RATINGS (Note 1)

Voltage

Logic Supply, VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7V

Output Supply, Vm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50V

Input Voltage

Note 1: All voltages are with respect to ground, Pins 4,

5, 12, 13. Currents are positive into, negative out of the

specified terminal. Pin numbers refer to DIL-16 pack-

age.

Consult Packaging Section of Databook for thermal limi-

tations and considerations of package.

Logic Inputs (Pins 7, 8, 9) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6V

Analog Input (Pin 10). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VCC

Reference Input (Pin 11) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15V

Input Current

Logic Inputs (Pins 7, 8, 9) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -10mA

Analog Inputs (Pins 10, 11). . . . . . . . . . . . . . . . . . . . . . . . . . . . -10mA

±

Output Current (Pins 1, 15) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2A

Junction Temperature, TJ. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +150°C

Storage Temperature Range, TS . . . . . . . . . . . . . . . . . . -55°C to +150°C

BLOCK DIAGRAM

4/97

1

UC3717A

CONNECTION DIAGRAMS

PACKAGE PIN FUNCTION

DIL-16 (TOP VIEW)

J or N Package

PLCC-20 (TOP VIEW)

Q Package

FUNCTION

N/C

1

BOUT

Timing

V^m

2

3

4

Gnd

N/C

5

6

Gnd

VCC

7

8

I1

9

Phase

N/C

I0

Current

VR

Gnd

N/C

Gnd

V^m

AOUT

Emitters

10

11

12

13

14

15

16

17

18

19

20

(Refer to the test circuit, Figure 6. Vm = 36V, VCC = 5V, VR = 5V, TA = 0°C to 70°C,

unless otherwise stated, TA = TJ.)

ELECTRICAL CHARACTERISTICS

PARAMETERS

Supply Voltage, Vm (Pins 3, 14)

Logic Supply Voltage, VCC (Pin 6)

Logic Supply Current, ICC (Pin 6)

Thermal Shutdown Temperature

Logic Inputs

TEST CONDITIONS

MIN

10

TYP

MAX UNITS

46

V

4.75

5.25

15

IO = I1 = 0

7

mA

°C

+160

2

+180

Input Low Voltage, (Pins 7, 8, 9)

Input High Voltage, (Pins 7, 8, 9)

Low Voltage Input Current, (Pins 7, 8, 9)

0.8

VCC

-100

-400

10

V

VI = 0.4V, Pin 8

VI = 0.4V, Pins 7 and 9

VI = 2.4V

µA

mA

µA

High Voltage Input Current, (Pins 7, 8, 9)

Comparators

Comparator Low, Threshold Voltage (Pin 10)

VR = 5V; IO = L; I1 = H

66

80

90

266

436

±20

35

mV

µA

µs

Comparator Medium, Threshold Voltage (Pin 10) VR = 5V; I_O= H; I1 = L

236

396

250

420

Comparator High, Threshold Voltage (Pin 10)

Comparator Input, Current (Pin 10)

Cutoff Time, tOFF

VR = 5V; IO = L; I1 = L

RT = 56kΩ, CT = 820pF

25

Turn Off Delay, tD

(See Figure 5)

2

µs

Source Diode-Transistor Pair

Saturation Voltage, VSAT (Pins 1, 15)

(See Figure 5)

Im = -0.5A,

Im = -1A,

Vm = 40V

Im = -0.5A

Im = -1A

Conduction Period

1.7

1.1

2.1

1.7

2.1

1.35

2.8

V

Recirculation Period

Conduction Period

Recirculation Period

Saturation Voltage, VSAT (Pins 1, 15)

(See Figure 5)

V

2.5

V

Leakage Current

300

1.25

1.7

µA

V

Diode Forward Voltage, VF

1

1.3

V

2

UC3717A

(Refer to the test circuit, Figure 6. VM = 36V, VCC = 5V, VR = 5V, TA = 0°C to 70°C, unless

otherwise stated, TA = TJ.)

ELECTRICAL

CHARACTERISTICS (cont.)

PARAMETERS

TEST CONDITIONS

MIN

TYP

MAX UNITS

Sink Diode-Transistor Pair

Saturation Voltage, VSAT (Pins 1, 15)

Im = 0.5A

Im = 1A

0.8

1.1

1.6

1.35

2.3

300

1.5

2

V

Leakage Current

Vm = 40V

Im = 0.5A

Im = 1A

µA

V

Diode Forward Voltage, V_F

1.1

1.4

V

Figure 1. Typical Source Saturation Voltage

vs Output Current (Recirculation Period)

Figure 2. Typical Source Saturation Voltage

vs Output Current (Conduction Period)

Figure 3. Typical Sink Saturation

Voltage vs Output Current

Figure 5. Typical Waveforms with MA Regulating

(phase = 0)

Figure 4. Typical Power Dissipation

vs Output Current

3

UC3717A

Figure 6. UC3717A Test Circuit

FUNCTIONAL DESCRIPTION

The UC3717A’s drive circuit shown in the block diagram

includes the following components.

saturation voltage of source transistor Q2 during recircu-

lation, thus improving efficiency by reducing power dissi-

pation.

(1) H-bridge output stage

(2) Phase polarity logic

(3) Voltage divider coupled with current sensing compa-

rators

(4) Two-bit D/A current level select

(5) Monostable generating fixed off-time

(6) Thermal protection

OUTPUT STAGE

The UC3717A’s output stage consists of four Darlington

power transistors and associated recirculating power di-

odes in a full H-bridge configuration as shown in Figure

7. Also presented, is the new added feature of inte-

grated bootstrap pull up, which improves device per-

formance during switched mode operation. While in

switched mode, with a low level phase polarity input, Q2

is on and Q3 is being switched. At the moment Q3 turns

off, winding current begins to decay through the commu-

tating diode pulling the collector of Q3 above the supply

voltage. Meanwhile, Q6 turns on pulling the base of Q2

higher than its previous value. The net effect lowers the

Note: Dashed lines indicate current decay paths.

Figure 7. Simplified Schematic of Output Stage

4

UC3717A

FUNCTIONAL DESCRIPTION (cont.)

PHASE POLARITY INPUT

ture to a maximum of 180C by reducing the winding cur-

rent.

The UC3717A phase polarity input controls current direc-

tion in the motor winding. Built-in hysteresis insures im-

munity to noise, something frequently present in

switched drive environments. A low level phase polarity

input enables Q2 and Q3 as shown in Figure 7. During

phase reversal, the active transistors are both turned off

while winding current delays through the commutating di-

odes shown. As winding current decays to zero, the inac-

tive transistors Q1 and Q4 turn on and charge the

winding with current of the reverse direction. This delay

insures noise immunity and freedom from power supply

current spikes caused by overlapping drive signals.

PERFORMANCE CONSIDERATIONS

In order to achieve optimum performance from the

UC3717A careful attention should be given to the follow-

ing items.

External Components: The UC3717A requires a mini-

mal number of external components to form a complete

control and switch drive unit. However, proper selection

of external components is necessary for optimum per-

formance. The timing pin, (pin 2) is normally connected

to an RC network which sets the off-time for the sink

power transistor during switched mode. As shown in Fig-

ure 8, prior to switched mode, the winding current in-

creases exponentially to a peak value. Once peak

current is attained the monostable is triggered which

turns off the lower sink drivers for a fixed off-time. During

off-time winding current decays through the appropriate

diode and source transistor. The moment off-time times

out, the motor current again rises exponentially produc-

ing the ripple waveform shown. The magnitude of wind-

ing ripple is a direct function of off-time. For a given

off-time TOFF, the values of RT and CT can be calculated

from the expression:

PHASE INPUT

LOW

Q1, Q4

OFF

Q2, Q3

ON

HIGH

ON

OFF

CURRENT CONTROL

The voltage divider, comparators, monostable, and two-

bit D/A provide a means to sense winding peak current,

select winding peak current, and disable the winding sink

transistors.

The UC3717A switched driver accomplishes current con-

trol using an algorithm referred to as "fixed off-time."

When a voltage is applied across the motor winding, the

current through the winding increases exponentially. The

current can be sensed across an external resistor as an

analog voltage proportional to instantaneous current.

This voltage is normally filtered with a simple RC low-

pass network to remove high frequency transients, and

then compared to one of the three selectable thresholds.

The two bit D/A input signal determines which one of the

three thresholds is selected, corresponding to a desired

winding peak current level. At the moment the sense volt-

age rises above the selected threshold, the UC3717A’s

monostable is triggered and disables both output sink

drivers for a fixed off-time. The winding current then cir-

culates through the source transistor and appropriate di-

ode. The reference terminal of the UC3717A provides a

means of continuously adjusting the current threshold to

allow microstepping. Table 1 presents the relationship

between the two-bit D/A input signal and selectable cur-

rent level.

T^OFF= 0.69R^TC^T

with the restriction that RT should be in the range of 10-

100k. As shown in Figure 5, the switch frequency FS is a

function of TOFF and TON. Since TON is a function of the

reference voltage, sense resistor, motor supply, and

winding electrical characteristics, it generally varies dur-

ing different modes of operation. Thus, FS may be ap-

proximated nominally as:

1

F^S= ⁄

(T^OFF).

1.5

Normally, Switch Frequency Is Selected Greater than

TABLE 1

IO

0

I1

0

1

CURRENT LEVEL

100%

1

60%

Figure 8. A typical winding current waveform. Wind-

ing current rises exponentially to a selected peak

value. The peak value is limited by switched mode

operation producing a ripple in winding current. A

phase polarity reversal command is given and wind-

ing current decays to zero, then increases exponen-

tially.

0

19%

1

Current Inhibit

OVERLOAD PROTECTION

The UC3717A is equipped with a new, more reliable ther-

mal shutdown circuit which limits the junction tempera-

5

UC3717A

FUNCTIONAL DESCRIPTION (cont.)

Low-pass filter components RC CC should be selected so

that all switching transients from the power transistors

and commutating diodes are well smoothed, but the pri-

mary signal, which can be in the range of 1/TOFF or

higher must be passed. Figure 5A shows the waveform

which must be smoothed, Figure 5B presents the desired

waveform that just smoothes out overshoot without radi-

cal distortion.

current is excessive and must be prevented. This is ac-

complished with switch drive by repetitively switching the

sink drivers on and off, so as to maintain an average

value of current equal to the rated value. This results in a

small amount of ripple in the controlled current, but the

increase in step rate and performance may be consider-

able.

Interference: Electrical noise generated by the chopping

action can cause interference problems, particularly in

the vicinity of magnetic storage media. With this in mind,

printed circuit layouts, wire runs and decoupling must be

considered. 0.01 to 0.1µF ceramic capacitors for high fre-

quency bypass located near the drive package across

V+ and ground might be very helpful. The connection

and ground leads of the current sensing components

should be kept as short as possible.

The sense resistor should be chosen as small as practi-

cal to allow as much of the winding supply voltage to be

used as overdrive to the motor winding. V , the voltage

RS

across the sense resistor, should not exceed 1.5V.

Voltage Overdrive: In many applications, maximum

speed or step rate is a desirable performance charac-

teristic. Maximum step rate is a direct function of the time

necessary to reverse winding current with each step. In

response to a constant motor supply voltage, the winding

current changes exponentially with time, whose shape is

determined by the winding time constant and expressed

as:

Half-Stepping: In half step sequence the power input to

the motor alternates between one or two phases being

energized. In a two phase motor the electrical phase shift

between the windings is 90°. The torque developed is the

vector sum of the two windings energized. Therefore

when only one winding is energized the torque of the mo-

tor is reduced by approximately 30%. This causes a

torque ripple and if it is necessary to compensate for this,

the VR input can be used to boost the current of the sin-

gle energized winding.

V^m

I^m=

−R^T

R [1−EXP ( ⁄ ]

L)

as presented in Figure 9. With rated voltage applied, the

time required to reach rated current is excessive when

compared with the time required with over-voltage ap-

plied, even though the time constant L/R remains con-

stant. With over-voltage however, the final value of

Figure 9. With rated voltage applied, winding current does not exceed rated value, but takes L/R seconds to

reach 63% of its final value - probably too long. Increased performance requires an increase in applied volt-

age, of overdrive, and therefore a means to limit current. The UC3717A motor driver performs this task effi-

ciently.

6

UC3717A

MOUNTING INSTRUCTIONS

12. The input can be controlled by a microprocessor,

TTL, LS, or CMOS logic.

The θJA of the UC3717AN plastic package can be re-

duced by soldering the GND pins to a suitable copper

area of the printed circuit board or to an external heat

sink. Due to different lead frame design, θJA of the ce-

ramic J package cannot be similarly reduced.

The diagram of Figure 11 shows the maximum package

power PTOT and the θJA as a function of the side " l " of

two equal square copper areas having a thickness of 35µ

(see Figure 10).

The timing diagram in Figure 13 shows the required sig-

nal input for a two phase, full step stepping sequence.

Figure 14 shows the required input signal for a one

phase-two phase stepping sequence called half-step-

ping.

The circuit of Figure 15 provides the signal shown in Fig-

ure 13, and in conjunction with the circuit shown in Fig-

ure 12 will implement a pulse-to-step two phase, full

step, bi-directional motor drive.

Figure 10. Example of P.C. Board Copper

Area which is used as Heatsink.

During soldering the pins’ temperature must not exceed

260°C and the soldering time must not be longer than 12

seconds.

The printed circuit copper area must be connected to

electrical ground.

Figure 12. Typical Chopper Drive for a Two

Phase Permanent Magnet Motor.

The schematic of Figure 16 shows a pulse to half step

circuit generating the signal shown in Figure 14. Care

has been taken to change the phase signal the same

time the current inhibit is applied. This will allow the cur-

rent to decay faster and therefore enhance the motor

performance at high step rates.

Figure 11. Maximum Package Power and Junction

to Ambient Thermal Resistance vs Side "l".

APPLICATIONS

A typical chopper drive for a two phase bipolar perma-

nent magnet or hybrid stepping motor is shown in Figure

7

UC3717A

Figure 13. Phase Input Signal for Two Phase Full Step Drive (4 Step Sequence)

Figure 14. Phase and Current-Inhibit Signal for Half-Stepping (8 Step Sequence)

Figure 15. Full Step, Bi-directional Two Phase Drive Logic

Figure 16. Half-Step, Bi-directional Drive Logic

UNITRODE CORPORATION

7 CONTINENTAL BLVD. • MERRIMACK, NH 03054

TEL. (603) 424-2410 • FAX (603) 424-3460

8

PACKAGE OPTION ADDENDUM

www.ti.com

6-May-2009

PACKAGING INFORMATION

Orderable Device

UC3717AN

Status ⁽¹⁾

ACTIVE

Package Package

Pins Package Eco Plan ⁽²⁾Lead/Ball Finish MSL Peak Temp ⁽³⁾

Qty

Type

Drawing

PDIP

N

16

20

25 Green (RoHS & CU NIPDAU N / A for Pkg Type

no Sb/Br)

UC3717ANG4

UC3717AQ

PDIP

PLCC

N

25 Green (RoHS & CU NIPDAU N / A for Pkg Type

no Sb/Br)

FN

46 Green (RoHS &

no Sb/Br)

CU SN

Level-2-260C-1 YEAR

UC3717AQG3

UC3717AQTR

UC3717AQTRG3

46 Green (RoHS &

no Sb/Br)

1000 Green (RoHS &

no Sb/Br)

1000 Green (RoHS &

no Sb/Br)

⁽¹⁾The marketing status values are defined as follows:

ACTIVE: Product device recommended for new designs.

LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.

NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in

a new design.

PREVIEW: Device has been announced but is not in production. Samples may or may not be available.

OBSOLETE: TI has discontinued the production of the device.

(2)

Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check

http://www.ti.com/productcontent for the latest availability information and additional product content details.

TBD: The Pb-Free/Green conversion plan has not been defined.

Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements

for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered

at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.

Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and

package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS

compatible) as defined above.

Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame

retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material)

(3)

MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder

temperature.

Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is

provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the

accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take

reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on

incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited

information may not be available for release.

In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI

to Customer on an annual basis.

Addendum-Page 1

PACKAGE MATERIALS INFORMATION

www.ti.com

6-Oct-2008

TAPE AND REEL INFORMATION

*All dimensions are nominal

Device

Package Package Pins

Type Drawing

SPQ

Reel

A0 (mm)

B0 (mm)

K0 (mm)

P1

W

Pin1

Diameter Width

(mm) W1 (mm)

(mm) (mm) Quadrant

UC3717AQTR

PLCC

FN

20

1000

330.0

16.4

10.3

4.9

12.0

16.0

Q1

Pack Materials-Page 1

PACKAGE MATERIALS INFORMATION

www.ti.com

6-Oct-2008

*All dimensions are nominal

Device

Package Type Package Drawing Pins

PLCC FN 20

SPQ

Length (mm) Width (mm) Height (mm)

346.0 346.0 33.0

UC3717AQTR

1000

Pack Materials-Page 2

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型号：	UC3717AN
厂家：	TEXAS INSTRUMENTS
描述：	Stepper Motor Drive Circuit 步进电机驱动电路运动控制电子器件信号电路光电二极管电动机控制电机驱动
文件：	总12页 (文件大小：648K)
中文：	中文翻译
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UC3717AN [TI]

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