gm1117-1.8tc3t Gamma Microelectronics, gm1117-1.8tc3t Datasheet - Page 7

• Manufacturer Part Number: gm1117-1.8tc3t
• Description: Gm1117 1.0a Low Dropout Precision Linear Regulators
• Manufacturer: Gamma Microelectronics

Protection Diodes
When large external capacitors are used with most
linear regulator, it is wise to add protection diodes. If
the input voltage of the regulator is shorted, the out-
put capacitor will discharge into the output of the reg-
ulator. The discharge current depends on the value
of capacitor, output voltage, and rate at which V
drops.
In the GM1117 linear regulators, the discharge path
is through a large junction, and protection diodes are
normally not needed. However, damage can occur if
the regulator is used with large output capacitance
values and the input voltage is instantaneously
shorted to ground. In this case, a diode connected
as shown above in Figure 2.
(a) Fixed Version
(b) Adjustable Version
V
IN
V
IN
Figure 2
C1
C1
MICROELECTRONICS
Large Output Capacitors
(a),(b)
V
A
V
IN
Protection Diode Scheme for
GM1117-Adj
IN
GM1117-3.3
IN4002
ADJ
IN4002
GND
C
ADJ
A
V
OUT
V
OUT
R2
R1
C2
V
C2
OUT
V
OUT
IN
1.0A LOW DROPOUT PRECISION LINEAR REGULATORS
Output Voltage Sensing
The GM1117 are three terminal regulators. For which,
they cannot provide true remote load sensing. Load
regulation is limited by the resistance of the conductors
connecting the regulator to the load. For best results
the GM1117 should be connected are as shown in
Figure 3.
Calculating Power Dissipation and Heat
Sink Requirements
The GM1117 precision linear regulators include thermal
shutdown and current limit circuitry to protect the de-
vices. However, high power regulators normally oper-
ate at high junction temperatures. It is important to cal-
culate the power dissipation and junction temperatures
accurately to be sure that you use and adequate heat
sink. The case is connected to V
and electrical isolation may be required for some appli-
cations. Thermal compound should always be used
with high current regulators like the GM1117.
(a) Fixed Version
(b) Adjustable Version
Figure 3
Minimized by this Grounding Scheme For Fixed
Power Management
V
IN
V
IN
(a),(b)
and Adjustable Output Regulators
Conductor Parasitic Resistance Effects are
V
V
IN
GM1117-3.3
IN
GM1117-Adj
GND
ADJ
V
V
OUT
OUT
OUT
R2
R1
R
R
C
C
on the GM1117,
Conductor
Parasitic
Resistance
Conductor
Parasitic
Resistance
GM1117
R
R
LOAD
LOAD
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