U3525-D16-T UTC [Unisonic Technologies], U3525-D16-T Datasheet - Page 7

• Manufacturer Part Number: U3525-D16-T
• Description: REGULATING PWM IC
• Manufacturer: UTC [Unisonic Technologies]

U3525
APPLICATION INFORMATION AND CIRCUIT
SHUTDOWN OPTIONS (see Block Diagram)
readily accept a pull-down signal which only has to sink a maximum of 100µA to turn off the outputs. This is
subject to the added requirement of discharging whatever external capacitance may be attached to these pins.
available shutdown options. Activating this circuit by applying a positive signal on Pin 10 performs two functions:
the PWM latch is immediately set providing the fastest turn-off signal to the outputs; and a 150µA current sink
begins to discharge the external soft-start capacitor. If the shutdown command is short, the PWM signal is
terminated without significant discharge of the soft-start capacitor, thus, allowing, for example, a convenient
implementation of pulse-by-pulse current limiting. Holding Pin 10 high for a longer duration, however, will
ultimately discharge this external capacitor, recycling slow turn-on upon release.
OSCILLATOR SCHEMATIC
Since both the compensation and soft-start terminals (Pins 9 and 8) have current source pull-ups, either can
An alternate approach is the use of the shutdown circuitry of Pin 10 which has been improved to enhance the
Pin 10 should not be left floating as noise pickup could conceivably interrupt normal operation.
V
REF
R
C
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
T
T
15
COMPARATOR
6
5
TO PWM
Q1
GND
400μA
Q3
Q2
Q8
Q6
SYNC.
Q4
2kΩ
1KΩ
Q9
2kΩ
Q10 Q11
14KΩ
Q12
Q5
25KΩ
Q13
Q7
Q14
DISCHARGE
Q15
LINEAR INTEGRATED CIRCUIT
7
1KΩ
Q16
5pF
23KΩ
7.4KΩ
3KΩ
Q17
4
TO OUTPUT
250Ω
CLOCK
BLANKING
QW-R103-032,A
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