ST5R25M Просмотр технического описания (PDF) - STMicroelectronics
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ST5R25M Datasheet PDF : 13 Pages
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ST5R00
ABSOLUTE MAXIMUM RATING
Symbol
Parameter
VOUT Output Voltage
VIN Input Voltage
VLX LX Pin Voltage
IL X LX Pin Output Current
Ptot Power Dissipation @ 25oC for SOT23-5L
Tstg Storage Temperature Range
Top Operating Junction Temperature Range
(*) Reduced by 1.7 mW for increasing in TA of 1oC over 25oC
Value
Unit
5. 5
V
5. 5
V
5. 5
V
Internally limited
170 (*)
mW
- 55 to 125
oC
- 25 to 85
oC
THERMAL DATA
Symbol
Parameter
Rthj- cas e Therma l Resistance Junction-case
SOT23-5L
63
SOT-89
17
Unit
°C/W
OPERATION
The ST5Rxx architecture is built around a VFM
CONTROL logic core: switching frequency is set
through a built in oscillator: TON time is fixed (Typ.
5µs) while TOFF time is determined by the error
amplifier output, a logic signal coming from the
comparison made by the Error Amplifier Stage
between the signal coming from the output
voltage divider network and the internal
Band-Gap voltage reference (Vref). TOFF reaches
a minimum (Typ. 1.7µs) when heavy load
conditions are met (Clock frequency 150KHz). An
over current conditions, through the internal
power switch, causes a voltage drop
VLX=RDSONxISW and the VLX limiter block forces
the internal switch to be off, so narrowing TON
time and limiting internal power dissipation. In this
case the switching frequency may be higher than
the 150KHz set by the internal clock generator.
VFM control ensures very low quiescent current
and high conversion efficiency even with very
light loads.
Since the Output Voltage pin is also used as the
device Supply Voltage, the versions with higher
output voltage present an higher internal supply
voltage that results in lower power switch RDSON,
slightly greater output power and higher
efficiency. Moreover, bootstrapping allows the
input voltage to sag to 0.6V (at IOUT=1mA) once
the system is started.
If the input voltage exceeds the output voltage,
the output will follow the input, however, the input
or output voltage must not be forced above 5.5V.
Typical Application Circuit
Typical Application Efficency
(*) See application info
2/13
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