ISSUED DATE :2005/01/24
REVISED DATE :
GT2123
Description
C M O S P o s i t i v e Vo l t a g e R eg u l a t o r
The GT2123 of positive, linear regulators feature low quiescent current (35 A typ.) with low dropout voltage,
making them ideal for battery applications.
This rugged device has both Thermal Shutdown, and Current Fold-back to prevent device failure under the
“Worst” of operating conditions.
The SOT-26 version also features a “Power Good” detector, which pulls low when the output is out of
regulation. The GT2123 is stable with an output capacitance of 2.2 F or greater.
Features
&
Low Dropout Voltage
Very
Functional Block Diagram
Applications
&
Battery Powered Widgets
&Instrumentation
&Wireless Devices
&PC Peripherals
&Portable Electronics
&Cordless Phones
&Electronic Scales
&Guaranteed 300mA output
&Over-Temperature Shutdown
&Current Limiting
&Short Circuit Current Fold-back
&Highly Accurate± 1.5%
&Adjustable output voltages
&Power-saving Shutdown Mode
&Power Good Detector
&Low Temperature coefficient
Package Dimensions
REF.
A
B
C
D
E
F
Millimeter
Min.
Max.
2.70
3.10
2.60
3.00
1.40
1.80
0.30
0.55
0
0.10
0°
10°
REF.
G
H
I
J
K
L
Dimensions
Millimeter
1.90 REF.
1.20 REF.
0.12 REF.
0.37 REF.
0.60 REF.
0.95 REF.
Typical Application Circuit
1/8
ISSUED DATE :2005/01/24
REVISED DATE :
Absolute Maximum Ratings
Parameter
Input
Max Voltage
Output Current
Input,
Output Voltage
Operating Ambient Temperature
Junction Temperature
Maximum Junction Temperature
Thermal Resistance
Power Dissipation( T=100 : )
EDS Classification
Symbol
V
IN
I
OUT
Topr
Tj
Tj
Max
ja
PD
V
IN
=5V,
Ratings
8
P
D
/( V
IN-
V
O)
GND-0.3 to V
IN
+0.3
-40 ~ +85
-40 ~ +125
150
260
380
B
Unit
V
mA
V
:
: /W
mW
Electrical Characteristics Ta=25
Parameter
Output Voltage
Output Current
Current Limit
Load Regulation
Dropout Voltage
Ground Pin Current
Line Regulation
Input
Voltage
Over Temperature Shutdown
Over Temperature Hysterisis
unless otherwise noted
Condition
Min
-1.5%
300
300
-
-
-
-
-
-
-
Note1
-
-
-
Symbol
V
O
I
O
I
LIM
REG
LOAD
V
DROPOUT
I
GND
REG
LINE
V
IN
OTS
OTH
TC
I
SC
PSRR
TYP
-
Max
1.5%
-
-
1
1300
400
300
-
0.15
0.1
7
-
-
-
300
-
-
-
-
-
1.23
V
IN
0.4
0.1
0.5
1
0.1
85
-
1
7
0.4
Unit
V
mA
mA
%
mV
A
%
V
:
:
ppm/ :
mA
dB
V
IN
=5V, I
O
=1mA
V
IN
=5V, V
O
>1.2
V
IN
=5V, V
O
>1.2
V
IN
=5V,
I
O
=1mA to 300mA
1.5V<V
O(NOM)
2.0V
I
O
=300mA
2.0V<V
O(NOM)
2.8V
V
O
=V
O(NOM)
-2%
2.8V<V
O(NOM)
<3.8V
V
IN
=5V,
I
O
=1mA~300mA
I
O
=5mA
V
O ˇ ¯ `
V
ˆ
V
IN
=V
OUT
(T)+1 to
V
O
2.0V
V
OUT
(T)+2
-
450
0.2
-
-
-
35
-
0.02
-
150
30
30
150
60
50
20
30
1
1.215
-
-
-
-
0.5
-
-
-
-
-
-
Output Voltage
Temperature Coefficient
Short Circuit Current
(Note2)
Power Supply Rejection
V
IN
=5V, V
OUT
<0.8V
f=100Hz
V
IN
=5V
Io=100mA
f=1kHz
Co=2.2 f
f=10kHz
f=10Hz~100kHz
Io=10mA
C
BYP
=0 F
Co=2.2 F
-
-
-
-
-
-
1.2
2.0
0
-
-
-
0
-
115
-
-
-
Output Voltage Noise
ADJ Input Bias Current
ADJ Reference Voltage
eN
I
ADJ
V
REF
V
EH
V
EL
I
EH
I
EL
I
SD
V
O,SD
V
UV
V
OV
I
LC
V
PG
V
OL
Vrms
A
Ø
V
V
A
A
A
V
%Vo
(NOM)
%Vo
(NOM)
A
V
V
EN
Input
Threshold
EN
Input
Bias Current
Shutdown Supply Current
Shutdown Output Voltage
Output Under Voltage
Output Over Voltage
PG Leakage Current
PG Voltage Rating
PG Voltage Low
Note 1: V
IN
(MIN)
=V
OUT
+V
DROPOUT
V
IN
=2.7V to 7V
V
IN
=2.7V to 7V
V
EN
=V
IN
, V
IN
=2.7V to 7V
V
EN
= 0V, V
IN
=2.7V to 7V
V
IN
=5V, V
O
=0V, V
EN
<V
EL
Io=35
A, V
EN
<V
EL
V
PG
=7V
V
O
in regulation
I
SINK
=0.4mA
2: To prevent the Short Circuit Current protection feature from being prematurely activated, the input voltage must be applied before
a current source load is applied.
2/8
ISSUED DATE :2005/01/24
REVISED DATE :
Ordering Information ( contd. )
Part Number
GT2123-AD
XXXX
Marking
3BAD2
Output Voltage
Adjustable
Part Number
Marking
Output Voltage
The GT2123 of COMS regulators contain a PMOS pass transistor, voltage reference, error amplifier,
over-current protection, thermal shutdown and Power Good detection circuitry.
The P-channel pass transistor receives data from the error amplifier, over-current shutdown, and thermal
protection circuits. During normal operation, the error amplifier compares the output voltage to a precision
reference. Over-current and Thermal shutdown circuits become active when the junction temperature exceeds
150 : , or the current exceeds 300mA. During thermal shutdown, the output voltage remains low. Normal
operation is restored when the junction temperature drops below 120 : .
The GT2123 switches from voltage mode to current mode when the load exceeds the rated output current.
This prevents over-stress. The GT2123 also incorporates current fold-back to reduce power dissipation when
the output is short circuited. This feature becomes active when the output drops below 0.8 volts, and reduces
the current flow by 65%. Full current is restored when the voltage exceeds 0.8 volts.
Detailed Description
The GT2123 is stable with an output capacitance to ground of 2.2 F or greater. Ceramic capacitors have the
lowest ESR, and will offer the best AC performance. Conversely, Aluminum Electrolytic capacitors exhibit the
highest ESR, resulting in the poorest AC response. Unfortunately, large value ceramic capacitors are
comparatively expensive. One option is to parallel a 0.1 F ceramic capacitor with a 10 F Aluminum Electrolytic.
The benefit is low ESR, high capacitance, and low overall cost.
A second capacitor is recommended between the input and ground to stabilize Vin. The input capacitor should
be at least 0.1 F to have a beneficial effect.
All capacitors should be placed in close proximity to the pins. A “Quiet” ground termination is desirable. This
can be achieved with a “Star” connection.
External Capacitors
The Enable pin normally floats high. When actively, pulled low, the PMOS pass transistor shuts off, and all
internal circuits are powered down. In this state, the quiescent current is less than 1 A. This pin behaves much
like an electronic switch.
Enable
Power Good
The GT2123 includes the Power Good feature. When the output is not within D
10% of the specified voltage, it
pulls low. This can occur under the following conditions:
1) Input Voltage too low.
2) During Over-Temperature.
3) During Over-Current.
4) If output is pulled up.
(Note: PG pin is an open-drain output.)
3/8
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