LM317MDT ON Semiconductor, LM317MDT Datasheet - Page 8

• Manufacturer Part Number: LM317MDT
• Description: Linear Regulators - Standard 500mA ADJ 1.2-37V
• Manufacturer: ON Semiconductor

Specifications of LM317MDT

• Polarity: Positive
• Number Of Outputs: 1
• Output Type: Adjustable
• Output Voltage: 1.2 V to 37 V
• Output Current: 0.25 A
• Line Regulation: 0.07 % / V
• Load Regulation: 1.5 % / V
• Input Voltage Max: 40 V
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: 0 C
• Package / Case: DPAK
• Mounting Style: SMD/SMT
• Reference Voltage: 1.3 V
• Voltage Regulation Accuracy: 4 %
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Basic Circuit Operation
operation, the LM317M develops and maintains a nominal
1.25 V reference (V
terminals. This reference voltage is converted to a
programming current (I
constant current flows through R
output voltage is given by:
error term in the equation, the LM317M was designed to
control I
this, all quiescent operating current is returned to the output
terminal. This imposes the requirement for a minimum load
current. If the load current is less than this minimum, the
output voltage will rise.
voltage differential across the circuit which is important to
performance, and operation at high voltages with respect to
ground is possible.
Load Regulation
load regulation, but a few precautions are needed to obtain
maximum performance. For best performance, the
programming resistor (R
the regulator as possible to minimize line drops which
effectively appear in series with the reference, thereby
degrading regulation. The ground end of R
near the load ground to provide remote ground sensing and
improve load regulation.
The LM317M is a three−terminal floating regulator. In
Since the current from the terminal (I
Since the LM317M is a floating regulator, it is only the
The LM317M is capable of providing extremely good
Adj
Figure 19. Basic Circuit Configuration
V
in
to less than 100 mA and keep it constant. To do
V
V out + V ref 1 )
ref
Adjust
= 1.25 V Typical
LM317M
ref
) between its output and adjustment
I
Adj
PROG
1
) should be connected as close to
) by R
V
V
ref
out
R 2
R 1
2
1
to ground. The regulated
(see Figure 19), and this
) I Adj R 2
+
R
R
Adj
I
2
1
PROG
2
APPLICATIONS INFORMATION
can be returned
) represents an
V
out
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8
External Capacitors
(C
impedance.
improve ripple rejection. This capacitor (C
ripple from being amplified as the output voltage is
increased. A 10 mF capacitor should improve ripple
rejection about 15 dB at 120 Hz in a 10 V application.
capacitance, like any feedback circuit, certain values of
external capacitance can cause excessive ringing. An output
capacitance (C
aluminum electrolytic capacitor on the output swamps this
effect and insures stability.
Protection Diodes
it is sometimes necessary to add protection diodes to prevent
the capacitors from discharging through low current points
into the regulator.
protection diodes for output voltages in excess of 25 V or
high capacitance values (C
D
short circuit. Diode D
discharging through the IC during an output short circuit.
The combination of diodes D
discharging through the IC during an input short circuit.
1
A 0.1 mF disc or 1.0 mF tantalum input bypass capacitor
The adjustment terminal may be bypassed to ground to
Although the LM317M is stable with no output
When external capacitors are used with any IC regulator
Figure 20 shows the LM317M with the recommended
in
prevents C
) is recommended to reduce the sensitivity to input line
C
in
Figure 20. Voltage Regulator with
V
O
in
O
from discharging thru the IC during an input
) in the form of a 1.0 mF tantalum or 25 mF
Adjust
Protection Diodes
1N4002
LM317M
D
1
2
R
protects against capacitor C
2
O
> 25 mF, C
1
R
and D
1
V
out
2
Adj
prevents C
C
Adj
D
> 5.0 mF). Diode
2
1N4002
Adj
+
C
) prevents
O
Adj
V
out
from
Adj