SG3731J Ver la hoja de datos (PDF) - Microsemi Corporation
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SG3731J Datasheet PDF : 5 Pages
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SG1731/SG2731/SG3731
ELECTRICAL CHARACTERISTICS (continued)
Parameter
Test Conditions
SHUTDOWN Section
Logic Threshold
SHUTDOWN HIGH Current
SHUTDOWN LOW Current
Output Drivers (Each Output)
-VS = -3.5V to -15V
VSHUTDOWN = -VS+2.4V
VSHUTDOWN = -VS
HIGH Output Voltage
LOW Output Voltage
Driver Risetime
Driver Falltime
Total Supply Current
ISOURCE = 20mA
ISOURCE = 100mA
ISINK = 20mA
ISINK = 100mA
C = 1000pF
L
CL = 1000pF
VS Supply Current
V Supply Current
O
VSHUTDOWN = -VS + 0.8V
V
= -V + 0.8V
SHUTDOWN
S
Note 3. These parameters, although guaranteed, are not tested in production.
Note 4. Unity Gain Inverting 10KΩ Feedback Resistance.
Note 5. VCM = ±12V.
SG1731/2731/3731 Units
Min. Typ. Max.
VS+0.8
VS+2.0 V
400 µA
-1.0 mA
19.2
V
19.0
V
-19.2 V
-19.0 V
300 ns
300 ns
14 mA
6 mA
APPLICATION INFORMATION
SUPPLY VOLTAGE
The SG1731 requires a supply voltage for the control circuitry (VS)
and for the power output drivers (VO). Each supply may be either
balanced positive and negative with respect to ground, or single-
ended. The only restrictions are:
1. The voltage between +VS and -VS must be at least 7.0V; but
no more than 44V.
2. The voltage between +V and -V must be at least 5.0V; but
O
O
no more than 44V.
3. +V must be at least 5V more positive than -V . This
O
S
eliminates the combination of a single-ended positive control
supply with a single-ended negative driver supply.
SUBSTRATE CONNECTION
The substrate connection (Pin 10) must always be connected to
either -VS or -VO, whichever is more negative. The substrate must
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 500µA current source, and an
external timing capacitor CT. A positive reference voltage (2V∆+)
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 peak-
to-peak voltage excursion and the value of C . The theoretical
T
expression for the oscillator period is:
T = 2CT dV
OSC 5 x 10-4
(Eq.1)
where CT is the timing capacitor in Farads and dV is VOSC in Volts
peak-to-peak.
As a design aid, the solutions to Equation 1 over the
recommended range of TOSCand VOSCare given in graphic form in
Figure 1. The lower limit on TOSC is 1.85µs, corresponding to a
maximum frequency of 350 KHz. The maximum value of V ,
OSC
(2V∆+) - (2V∆-), is 10V peak-to-peak for linear waveforms.
FIGURE 1 - SG1731 OSCILLATOR PERIOD VS. VOSC AND CT
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 will determine the
S
input common mode range and output voltage swing; both will
extend to within 3V of the VS supply.
PULSE WIDTH MODULATION
Pulse width modulation occurs by comparing the triangle
waveform to a fixed upper (+VT) and lower (-VT) threshold
voltage. A crossing above the upper threshold causes
Output A to switch to the HIGH state, and a crossing below
4/90 Rev 1.3 9/99
Copyright 1999
LINFINITY Microelectronics Inc.
3
11861 Western Avenue ∞ Garden Grove, CA 92841
(714) 898-8121 ∞ FAX: (714) 893-2570
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