 Product Pages:
ST890B ST890C
ST890 is a low-voltage, P-channel MOSFET power switch intended for high-side
load-switching applications. This switch operates with inputs from +2.7V
to +5.5V, making it ideal for both +3V and +5V systems. Internal current-limiting
circuitry protects the voltage supply input against overload. Thermal-overload
protection limits power dissipation and junction temperature.
ST890 limits currents up to 1.2A. The current limit through the switch
is programmed by a resistor connected to the SET pin to the ground. When
the output current is increased beyond the programmed current limit, or
1.2A, the current also increases through the replica switch (IOUT/1110)
and through RSET.
The current-limit error amplifier compares the voltage across RSET to
the internal +1.24V reference and regulates the current back to the lower
programmed limit or 1.2A. This switch is not bi-directional; therefore,
the input voltage must be higher than the output voltage.
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2.7V to 5.5V input range
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Programmable current limit up to 1.2A
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Low quiescent current
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Thermal shutdown
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FAULT indicator output
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90m (typ) on-resistance (Vin=3V)
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SO-8 package
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Price effective
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Market standard fully compliant
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Portable equipment
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PCMCIA slots
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Access bus slots
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Point of deployment slot in set-top-boxes
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Current-limit switch is digitally programmable
| Settings the current limit |
The current limit of ST890 can be programmed with the SET pin. This pin
is internally connected to both the current mirror, that divides the IOUT
by 1110, and to the error amplifier that provides the difference between
the reference voltage and the voltage VSET of the SET pin. The formula
to calculate RSET is: RSET= VSET / ISET
RSET = VSET / 1110 . .
then: RSET= 1.38 x 103 / ILIMIT
| MAXIM |
| E = -40°C to +85°C
S = SO |
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