SG2524P STMicroelectronics, SG2524P Datasheet - Page 5

• Manufacturer Part Number: SG2524P
• Description: PMIC Solutions SO-16 REGULATED PWM
• Manufacturer: STMicroelectronics

Specifications of SG2524P

• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

PRINCIPLES OF OPERATION
The SG2524/3524 is a fixed frequency pulse-
with-modulation voltage regulator control circuit.
The regulator operates at a frequency that is pro-
grammed by one timing resistor (R
ing capacitor (C
charging current for C
voltage ramp at C
tor providing linear control of the output pulse
width by the error amplifier. the SG2524/3524
contains, an on-board 5V regulator that serves as
a
SG2524/3524’s internal control circuitry and is
also useful in supplying external support functions.
This reference voltage is lowered externally by a
resistor divider to provide a reference within the
common mode range the error amplifier or an ex-
ternal reference may be used. The power supply
output is sensed by a second resistor divider net-
work to generale a feedback signal to error ampli-
fier. The amplifier output voltage is then com-
pared to the linear voltage ramp at C
resulting modulated pulse out of the high-gain
comparator is then steered to the appropriate out-
put pass transistors (Q
steering flip-flop, which is synchronously toggled
by the oscillator output. The oscillator output
pulse also serves as a blanking pulse to assure
both output are never on simultaneously during
the transition times. The width of the blanking
pulse is controlled by the value of C
may be applied in a push-pull configuration in
which their frequency is half that of the base oscil-
lator, or paralleled for single-ended applications in
which the frequency is equal to that of the oscilla-
tor. The output of the error amplifier shares a
common input to the comparator with the current
limiting at shutdown circuitry and can be overrid-
den by signals from either of these inputs. This
common point is also available externally and
may be employed to control the gain of, or to
compensate, the error amplifier, or to provide ad-
ditional control to the regulator.
RECOMMENDED OPERATING CONDITIONS
TYPICAL APPLICATIONS DATA
OSCILLATOR
The oscillator controls the frequency of the
Supply voltage V
Reference Output Current
Current trough C
Timing Resistor, R
Timing Capacitor, C
reference
T
IN
as
T
Terminal
T
T
). R
T
, which is fed to the compara-
well
T
T
. This results in a linear
A
established a constant
or Q
as
B
0.001 to 0.1 F
- 0.03 to -2mA
1.8 to 100K
) by the pulse-
powering
0 to 20mA
T
8 to 40V
T
) and one tim-
. The outputs
T
. The
the
SG2524 and is programmed by R
cording to the approximate formula:
where:
R
C
f is in KHz
Pratical values of C
0.1 F. Pratical values of R
100K . This results in a frequency range typically
from 120Hz to to 500KHz.
BLANKING
The output pulse of oscillator is used as a blank-
ing pulse at the output. This pulse width is con-
trolled by the value of C
required for frequency control, the oscillator out-
put pulse width may still be increased by applying
a shunt capacitance of up to 100pF from pin 3 to
ground. If still greater dead-time is required, it
should be accomplished by limiting the maximum
duty cycle by clamping the output of the error am-
plifier. This can easily be done with the circuit be-
low:
Figure 6.
SYNCRONOUS OPERATION
When an external clock is desired, a clock pulse
of approximately 3V can be applied directly to the
oscillator output terminal. The impedance to
ground at this point is approximately 2K . In this
configuration R
period slightly greater than that the external clock.
If two more SG2524 regulators are to be operated
synchronously, all oscillator output terminals
should be tied together, all C
nected to a single timing capacitor, and timing re-
sistor connected to a single R
other R
V
tween the C
REF
T
T
is in K
is in F
. Minimum lead lengths should be used be-
T
terminals can be left open or shorted to
T
terminals.
T
C
T
f
must be selected for a clock
T
R
T
1.18
fall between 0.001 and
.If small values of C
T
C
T
T
SG2524 - SG3524
fall between 1.8 and
T
T
terminals con-
T
terminal. The
and C
T
T
ac-
are
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