SG2731 Microsemi Corporation, SG2731 Datasheet - Page 3

• Manufacturer Part Number: SG2731
• Description: Dc Motor Pulse Width Modulator
• Manufacturer: Microsemi Corporation

4/90 Rev 1.3 9/99
Copyright
ELECTRICAL CHARACTERISTICS
Note 3. These parameters, although guaranteed, are not tested in production.
Note 4. Unity Gain Inverting 10K
APPLICATION INFORMATION
SUPPLY VOLTAGE
The SG1731 requires a supply voltage for the control circuitry (V
and for the power output drivers (V
balanced positive and negative with respect to ground, or single-
ended. The only restrictions are:
SUBSTRATE CONNECTION
The substrate connection (Pin 10) must always be connected to
either -V
also be well bypassed to ground with a high quality capacitor.
OSCILLATOR
The triangle oscillator consists of two voltage comparators, a set/
reset flip-flop, a bi-directional 500 A current source, and an
external timing capacitor C
applied to Pin 2 determines the positive peak value of the triangle,
and a negative reference voltage (2V
peak value of the triangle waveform.
Since the value of the internal current source is fixed at a nominal
±500 A, the oscillator period is a function of the selected peak-
to-peak voltage excursion and the value of C
expression for the oscillator period is:
where C
peak-to-peak.
SHUTDOWN Section
Logic Threshold
SHUTDOWN HIGH Current
SHUTDOWN LOW Current
Output Drivers (Each Output)
HIGH Output Voltage
LOW Output Voltage
Driver Risetime
Driver Falltime
Total Supply Current
V
V
1. The voltage between +V
2. The voltage between +V
3. +V
S
O
Supply Current
Supply Current
no more than 44V.
no more than 44V.
eliminates the combination of a single-ended positive control
supply with a single-ended negative driver supply.
1999
O
S
T
must be at least 5V more positive than -V
or -V
is the timing capacitor in Farads and dV is V
O
, whichever is more negative. The substrate must
T
Parameter
OSC
=
5 x 10
2C
T
. A positive reference voltage (2V
S
O
T
and -V
and -V
dV
Feedback Resistance.
-4
O
). Each supply may be either
S
O
-
) at Pin 7 sets the negative
must be at least 7.0V; but
must be at least 5.0V; but
(continued)
T
. The theoretical
-V
V
V
I
I
I
I
C
C
V
V
SOURCE
SOURCE
SINK
SINK
SHUTDOWN
SHUTDOWN
SHUTDOWN
SHUTDOWN
L
L
OSC
S
= 1000pF
= 1000pF
(Eq.1)
= -3.5V to -15V
= 20mA
= 100mA
S
. This
in Volts
= 20mA
= 100mA
= -V
= -V
= -V
= -V
+
S
)
)
S
S
S
S
3
+2.4V
+ 0.8V
+ 0.8V
Test Conditions
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
ERROR AMPLIFIER
The error amplifier of the SG1731 is a conventional internally-
compensated 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
extend to within 3V of the V
PULSE WIDTH MODULATION
Pulse width modulation occurs by comparing the triangle
waveform to a fixed upper (+V
voltage.
Output A to switch to the HIGH state, and a crossing below
Note 5. V
+
) - (2V
A crossing above the upper threshold causes
FIGURE 1 - SG1731 OSCILLATOR PERIOD VS. V
CM
-
), is 10V peak-to-peak for linear waveforms.
= 12V.
SG1731/SG2731/SG3731
OSC
S
11861
and V
supply.
OSC
Western
T
OSC
is 1.85 s, corresponding to a
V
) and lower (-V
SG1731/2731/3731
Min. Typ. Max.
19.2
19.0
S
+0.8
L
are given in graphic form in
[phone]
INFINITY
Avenue
S
will determine the
OSC
V
Garden
-19.2
-19.0
AND C
-1.0
400
300
300
S
14
+2.0
6
Microelectronics
T
) threshold
FAX: [phone]
T
Grove,
Units
mA
mA
mA
ns
ns
V
V
V
V
V
CA
A
OSC
92841
,
Inc.