si-8090jd Allegro MicroSystems, Inc., si-8090jd Datasheet - Page 5

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si-8090jd

Manufacturer Part Number
si-8090jd
Description
Step-down To 9.0 V, 1.5 A, Dc/dc Converter
Manufacturer
Allegro MicroSystems, Inc.
Datasheet

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Part Number
Manufacturer
Quantity
Price
Part Number:
SI-8090JD
Manufacturer:
SANKEN
Quantity:
20 000
Input Capacitor (C1). Capacitors with low impedance
for high-frequency ripple current must be used.
Output Capacitor (C2). Capacitors with low impedance
for high-frequency ripple current must be used. Especially
when the C2 impedance is high, the switching waveform
may not be normal at low temperatures. Film or tantalum
capacitor for C2 may cause abnormal oscillations.
Catch Diode (D1). Diode D1 must be a Schottky diode.
Other diode types will result in increased forward voltage
spikes, reverse current flow, increased IC power dissipa-
tion during the off period, and possible destruction of the
IC.
Choke Coil (L1). If the winding resistance of the choke
coil is too high, the circuit efficiency will decrease. As the
overcurrent protection start current is approximately 2.5 A,
attention must be paid to the heating of the coil by magnetic
saturation due to overload. To reduce the output ripple, the
inductor may be increased at the expense of excessive
board area and cost.
www.allegromicro.com
SI-8090JD
APPLICATIONS INFORMATION
Soft-Start Capacitor (C3). Soft start for the converter
is enabled by connecting a capacitor between terminal 5
and ground. The converter may be turned off by decreasing
the terminal 5 voltage below 0.5 V with either an npn
small-signal transistor or the output of open-collector TTL.
If both a large soft-start capacitor and on/off control are
desired, collector current limiting must be used to prevent
transistor damage. No external voltage can be applied to
terminal 5.
Parallel Operation. Parallel operation to increase load
current is not permitted.
Overcurrent Protection. The SI-8000JD series has a
built-in fold-back type overcurrent protection circuit, which
limits the output current at a start-up mode. It thus cannot
be used in applications that require current at the start-up
mode such as:
(1) constant-current load,
(2) power supply with positive and negative outputs to
common load (a center-tap type power supply), or
(3) raising the output voltage by putting a diode or a
resistor between the device ground and system ground.
Typical Application
DC/DC Converter
to 9.0 V, 1.5 A,
SI-8090JD
Step-Down
5

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