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LM1086 View Datasheet(PDF) - HTC Korea

Part Name
Description
Manufacturer
LM1086 Datasheet PDF : 8 Pages
1 2 3 4 5 6 7 8
1.5A L.D.O. VOLTAGE REGULATOR (Adjustable & Fixed)
RIPPLE REJECTION
LM1086
The ripple rejection values are measured with the adjustment pin bypassed. The impedance of the
adjust pin capacitor at the ripple frequency should be less than the value of R1 (normally 100Ω
to 120Ω) for a proper bypassing and ripple rejection approaching the values shown. The size of
the required adjust pin capacitor is a function of the input ripple frequency. If R1=100Ω at 120Hz
the adjust pin capacitor should be 25uF. At 10kHz only 0.22uF is needed.
The ripple rejection will be a function of output voltage, in circuits without an adjust pin bypass
capacitor. The output ripple will increase directly as a ratio of the output voltage to the reference
voltage (Vout/Vref)
OUTPUT VOLTAGE
LM1086
The LM1086 series develops a 1.25V reference voltage
between the output and the adjust terminal. Placing a
resistor between these two terminals causes a constant
current to flow through R1 and down throuth R2 to set the
overall output voltage.
This current is normally the specified minium load current
of 10mA. Because IADJ is very small and constant it
represents a small error and it can usually be ignored.
LOAD REGULATION
LM1086
True remote sheet specification it is not possible to
provide, because the LM1086 is a three terminal device.
The resistance of the wire connecting the regulator to the
load will limit the load regulation.
The data sheet specification for load regulation is measured
at the bottom of the package. Negative side sensing is a
true Kelvin connection, with the bottom of the output divider
returned to the negative side of the load.
The best load regulation is obtained when the top of the
resistor divider R1 is connected directly to the case not to
the load. If R1 were connected to the load, the effective
resistance between the regulator and the load would be:
[RPX(R2+R1)]/R1 , R P = Parasitic Line Resistance
Connected as shown Fig.3 RP is not multiplied by the divider ratio. Using 16-gauge wire the
parasitic line resistance is about 0.004Ω per foot, transllating to 4mV/ft at 1A load current.
-7-
HTC
 

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