L1136_12 Datasheet, PDF (8/9 Pages) Unisonic Technologies – HIGH RIPPLE-REJECTION LOW DROPOUT HIGH OUTPUT CURRENT CMOS VOLTAGE REGULATOR

L1136
Preliminary
CMOS IC
„ FUNCTIONAL DESCRIPTION
1. Basic Operation
The UTC L1136‘s block diagram is shown in the following. (Fig.1)
The UTC L1136 has an error amplifier, and it compares the reference voltage (V_REF) with V_FB, which is the
output voltage resistance-divided by feedback resistors R_S and R_F. It supplies the gate voltage necessary to
maintain the constant output voltage which is not influenced by the input voltage and temperature change, to the
output transistor.
V_IN
Current
Supply
V_REF
Error Amplifier
-
+
Parasitic
Diode
V_OUT
R_F
V_FB
Reference
Voltage Circuit
R_S
V_SS
Fig.1
2. Output Transistor
For L1136, the output transistor is a P-channel MOSFET with low on-resistance.
In order to protect against inverse current, make sure that V_OUT does not exceed V_IN+0.3V, because of a
parasitic diode between the V_IN and V_OUT pin, when the potential of V_OUT became higher than V_IN.
3. Shutdown Pin (ON/OFF pin)
The shutdown pin is used to turn on and turn off this regulator.
When the ON/OFF pin is set to the shutdown level, the entire internal circuit stops operating. For reducing the
current dissipation, the internal P-channel MOSFET is shut down. The V_OUT pin is set to the V_SS level by the internal
dividing resistor of several hundred kΩ between the V_OUT and V_SS pin.
Note: When the ON/OFF pin voltage is in the range of 0.3V~1.0V, the current dissipation increases. The
architecture of the ON/OFF pin can be seen in Fig. 2 Since the ON/OFF pin is neither pulled down nor pulled up
internally, do not use it in the floating state.
ON/OFF Pin
“L”: Power off
“H”: Power on
Internal Circuits
Stop
Operate
V_OUT Pin Voltage
V_SS level
Set value
Current Consumption
I_SS2
I_SS1
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
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QW-R502-464.e