Datasheet SG1731J, SG1731J-883B, SG2731J, SG2731N, SG3731J Datasheet (Microsemi Corporation)

SG1731/SG2731/SG3731

DC MOTOR PULSE WIDTH MODULATOR

DESCRIPTION

The SG1731 is a pulse width modulator circuit designed specifically for DC motor
control. It provides a bi-directional pulse train output in response to the magnitude
and polarity of an analog error signal input. The device is useful as the control
element in motor-driven servo systems for precision positioning and speed control,
as well as in audio modulators and amplifiers using carrier frequencies to 350 KHz.

The circuit contains a triangle waveform oscillator, a wideband operational amplifier
for error voltage generation, a summing/scaling network for level-shifting the
triangle waveform, externally programmable PWM comparators and dual ±100mA,
±22V totem pole drivers with commutation diodes for full bridge output. A
SHUTDOWN terminal forces the drivers into a floating high-impedance state when
driven LOW. Supply voltage to the control circuitry and to the output drivers may be
from either dual positive and negative supplies, or single-ended.

BLOCK DIAGRAM

FEATURES

••

±±

•

±3.5V to

••

±±

••

±±

•

±2.5V to

••

±±

••

• Dual 100mA source/sink output

••

drivers

••

• 5KHz to 350KHz oscillator range

••

••

• High slew rate error amplifier

••

••

• Adjustable deadband operation

••

••

• Digital SHUTDOWN input

••

±±

±15V control supply

±±
±±

±22V driver supply

±±

HIGH RELIABILITY FEATURES

- SG1731

♦♦

♦ Available to MIL-STD-883

♦♦
♦♦

♦ LMI level “S” processing available

♦♦

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ABSOLUTE MAXIMUM RATINGS (Note1)

Supply Voltage (±VS) ........................................................ ±18V

Analog Inputs....................................................................... ±V

Digital Inputs (SHUTDOWN) .................... -VS-0.3V to -VS+18V

Output Driver Supply Voltage (±V

Source/Sink Output Current (continuous) .................... 200mA

) ................................. ±25V

O

Source/Sink Output Current (peak, 500ns).................. 400mA

Note 1. Values beyond which damage may occur.

THERMAL DATA

SG1731/SG2731/SG3731

Output Driver Diode Current (continuous) .................... 200mA

Output Driver Diode Current (peak, 500ns) .................. 400mA

S

Operating Junction Temperature

Hermetic (J - Package) ............................................... 150°C

Plastic (N - Package) .................................................. 150 °C

Storage Temperature Range ............................ -65°C to 150°C

Lead Temperature (Soldering, 10 Seconds) .................. 300 °C

J Package:

Thermal Resistance-Junction to Case, θ

Thermal Resistance-Junction to Ambient, θJA.......... 80°C/W

.............. 30°C/W

JC

N Package:

Thermal Resistance-Junction to Case, θ

Thermal Resistance-Junction to Ambient, θJA......... 65°C/W

.............. 40°C/W

JC

Note A. Junction Temperature Calculation: TJ = TA + (PD x θJA).
Note B. The above numbers for θ

resistance of the package in a standard mounting configuration.
The θJA numbers are meant to be guidelines for the thermal
performance of the device/pc-board system. All of the above
assume no ambient airflow.

are maximums for the limiting thermal

JC

RECOMMENDED OPERATING CONDITIONS (Note 2)

Supply Voltage Range (±VS)............................... ±3.5V to ±15V

Error Amp Common-Mode Range ............... -VS + 3V to VS - 3V

Output Driver Supply Voltage Range.................. ±2.5V to ±22V

Source/Sink Output Current (continuous) .................... 100mA

Source/Sink Output Current (peak, 500ns) .................. 200mA

Output Driver Diode Current (continuous) .................... 100mA

Output Driver Diode Current (peak, 500ns) .................. 200mA

Note 2. Range over which the device is functional and parameter limits are guaranteed.

Oscillator Frequency Range ........................... 10Hz to 350KHz

Oscillator Voltage (Peak-to-Peak) .............................1V to 10V

Oscillator Timing Capacitor (CT) ....................... 200pF to 2.5µF

Operating Ambient Temperature Range

SG1731 ........................................................ -55°C to 125°C

SG2731 ........................................................... -25°C to 85°C

SG3731 .............................................................. 0°C to 70°C

ELECTRICAL CHARACTERISTICS

(Unless otherwise specified, these specfiications apply over the operating ambient temperatures for SG1731 with -55°C ≤ TA ≤ 125°C, SG2731 with

-25°C ≤ TA ≤ 85°C, SG3731 with 0°C ≤ TA ≤ 70°C, VS = ±15V, and VO = ±22V. Low duty cycle pulse testing techniques are used which maintains junction
and case temperatures equal to the ambient temperature.)

Parameter Units

Oscillator Section

CT Charging Current
2V∆± Input Bias Current

Initial Oscillator Frequency
Temperature Stability

(Note 3)

TA = 25°C
TA = T

MIN

VCM = ±5V
CT = 1000pF, 2V∆± = ±5V,TA = 25°C
CT = 1000pF, 2V∆± = ±5V

Error Amplifier Section (Note 5)

Input Offset Voltage
Input Bias Current
Input Offset Current
Open Loop Voltage Gain
Output Voltage Swing

RL = 2KΩ

RL = 2KΩ
Common-Mode Rejection Ratio
Slew Rate (Notes 3 and 4)
Unity Gain Bandwidth (Notes 3 and 4)

TA = 25°C

TA = 25°C

PWM Comparators

Input Bias Current 6 µA±VT = ±3V

Test Conditions

to T

MAX

SG1731/2731/3731

Min. Typ. Max.

500

450
400

550
600

-20

25.0

22.5

27.5
10

10

3

600

70

±10

70

5

10

0.7

1

µA
µA
µA

KHz

%

mV

µA
nA
dB

V

dB
V/µs
MHz

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ELECTRICAL CHARACTERISTICS (continued)

SG1731/SG2731/SG3731

Parameter

SHUTDOWN Section

Logic Threshold
SHUTDOWN HIGH Current
SHUTDOWN LOW Current

= -3.5V to -15V

-V

S

V

SHUTDOWN

V

SHUTDOWN

= -VS+2.4V
= -V

S

Output Drivers (Each Output)

HIGH Output Voltage
LOW Output Voltage
Driver Risetime

Driver Falltime

= 20mA

I

SOURCE

= 100mA

I

SOURCE

I

= 20mA

SINK

I

= 100mA

SINK

CL = 1000pF
CL = 1000pF

Total Supply Current

VS Supply Current
VO Supply Current

Note 3. These parameters, although guaranteed, are not tested in production.
Note 4. Unity Gain Inverting 10KΩ Feedback Resistance.

V

SHUTDOWN

V

SHUTDOWN

= -VS + 0.8V
= -VS + 0.8V

APPLICATION INFORMATION

SUPPLY VOLTAGE

The SG1731 requires a supply voltage for the control circuitry (V
and for the power output drivers (V

). Each supply may be either

O

balanced positive and negative with respect to ground, or single­ended. The only restrictions are:

1.The voltage between +V

and -VS must be at least 7.0V; but

S

no more than 44V.

2.The voltage between +VO and -VO must be at least 5.0V; but
no more than 44V.

must be at least 5V more positive than -VS. This

3.+V

O

eliminates the combination of a single-ended positive control
supply with a single-ended negative driver supply.

)

S

Test Conditions Units

Note 5. VCM = ±12V.

SG1731/2731/3731

Min. Typ. Max.

VS+0.8

VS+2.0

400

-1.0

19.2

19.0

-19.2

-19.0
300
300

14

6

V

µA

mA

V
V
V

V
ns
ns

mA
mA

As a design aid, the solutions to Equation 1 over the
recommended range of T
Figure 1. The lower limit on T
maximum frequency of 350 KHz. The maximum value of V
(2V

∆+) - (2V∆-), is 10V peak-to-peak for linear waveforms.

OSC

and V

are given in graphic form in

OSC

is 1.85µs, corresponding to a

OSC

OSC

,

SUBSTRATE CONNECTION

The substrate connection (Pin 10) must always be connected to
either -V

or -VO, whichever is more negative. The substrate must

S

also be well bypassed to ground with a high quality capacitor.

OSCILLATOR

FIGURE 1 - SG1731 OSCILLATOR PERIOD VS. V

OSC

AND C

T

ERROR AMPLIFIER

The triangle oscillator consists of two voltage comparators, a set/
reset flip-flop, a bi-directional 500µA current source, and an
external timing capacitor C

. A positive reference voltage (2V∆+)

T

applied to Pin 2 determines the positive peak value of the triangle,
and a negative reference voltage (2V∆-) at Pin 7 sets the negative
peak value of the triangle waveform.
Since the value of the internal current source is fixed at a nominal
±500µA, the oscillator period is a function of the selected peak­to-peak voltage excursion and the value of C

. The theoretical

T

expression for the oscillator period is:

2CT dV

= (Eq.1)

T

OSC

where CT is the timing capacitor in Farads and dV is V

5 x 10

-4

in Volts

OSC

peak-to-peak.

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The error amplifier of the SG1731 is a conventional internally­compensated operational amplifier with low output impedance.
All of the usual feedback and frequency compensation
techniques may be use to control the closed-loop gain
characteristics. The control supply voltage ±V
input common mode range and output voltage swing; both will

will determine the

S

extend to within 3V of the VS supply.

PULSE WIDTH MODULATION

Pulse width modulation occurs by comparing the triangle
waveform to a fixed upper (+V

) and lower (-VT) threshold

T

voltage. A crossing above the upper threshold causes
Output A to switch to the HIGH state, and a crossing below

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APPLICATION INFORMATION (continued)

the lower threshold causes Output B to switch to the HIGH state.
If ±V

is less than ±8V then ±VT can be obtained with resistors from

S

. If ±VS is greater than ±8V use zeners.

±V

S

Threshold crossings are generated by shifting the triangle
waveform up and down with the error voltage (Pin 5). A positive
error voltage will result in a pulse width modulated output at
Driver A (Pin 13). Similarly, a negative error voltage produces a
pulse train at Driver B (Pin 12). Figure 2 illustrates this process
for the case where V

∆+ is greater than V

It is important to note that the triangle shifting circuit also
attenuates the waveform seen at C
in a waveform at the PWM comparators with a positive peak of
V∆+ and a negative peak of V
when selecting the values for +V

∆-, and must be taken into account

and -VT.

T

.

T

by a factor of 2. This results

T

SG1731/SG2731/SG3731

APPLICATION CIRCUITS

FIGURE 2 - PULSE WIDTH MODULATION WITH NO DEADBAND

FIGURE 3

In this simple battery-powered position servo, the control supply
and driver supply are both single-ended positive with respect to

A high torque position servo is obtained by buffering the output
drivers to obtain higher output current.

FIGURE 4

ground.

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APPLICATION CIRCUITS

SG1731/SG2731/SG3731

FIGURE 5

Bi-directional speed control results when the feedback voltage
transducer is a tachometer.

The two-quadrant transfer function of the SG1731 is ideal for
pulse width modulated audio power amplifiers.

CONNECTION DIAGRAMS & ORDERING INFORMATION (See Note Below)

Ambient

Temperature Range

Connection Diagram

16-PIN CERAMIC DIP
J - PACKAGE

16-PIN PLASTIC DIP
N - PACKAGE

Part No.Package

SG1731J/883B -55°C to 125°C
SG1731J -55°C to 125°C
SG2731J -25°C to 85°C
SG3731J 0°C to 65°C

SG2731N -25°C to 85°C
SG3731N 0°C to 65°C

FIGURE 6

1916

+V

T

2

2V∆+ SHUTDOWN
N. I. INPUT +V
INV. INPUT

ERROR

C

T

2V∆-

-V

T

15

14

3
4

13

5

12

11

6

10

7
8

+V

S

O

OUTPUT A
OUTPUT B

-V

O

SUBSTRATE

-V

S

Note 1. All packages are viewed from the top.
Note 2. Contact factory for flatpack and leadless chip carrier availability.

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