IC LDO 3.3V 3A SHUTDOWN DDPAK-5

LT1529CQ-3.3#TR

Manufacturer Part NumberLT1529CQ-3.3#TR
DescriptionIC LDO 3.3V 3A SHUTDOWN DDPAK-5
ManufacturerLinear Technology
LT1529CQ-3.3#TR datasheet
 


Specifications of LT1529CQ-3.3#TR

Regulator TopologyPositive FixedVoltage - Output3.3V
Voltage - InputUp to 15VVoltage - Dropout (typical)0.6V @ 3A
Number Of Regulators1Current - Output3A
Current - Limit (min)3.2AOperating Temperature0°C ~ 125°C
Mounting TypeSurface MountPackage / CaseTO-263-5, D²Pak (5 leads + Tab), TO-263BA
Lead Free Status / RoHS StatusContains lead / RoHS non-compliant  
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LT1529
LT1529-3.3/LT1529-5
U
U
U
PI FU CTIO S
function of voltage appears in the Typical Performance
Characteristics. If the SHDN pin is not used it can be left
open circuit. The device will be active, output on, if the
SHDN pin is not connected.
V
(Pin 5): Input Pin. Power is supplied to the device
IN
through the V
pin. The V
pin should be bypassed to
IN
IN
ground if the device is more than six inches away from the
main input filter capacitor. In general, the output imped-
ance of a battery rises with frequency so it is advisable to
O
U
U
A
PPLICATI
S
I FOR ATIO
The LT1529 is a 3A low dropout regulator with mi-
cropower quiescent current and shutdown capable of
supplying 3A of output current at a dropout voltage of
0.6V. The device operates with very low quiescent current
(50µA). In shutdown the quiescent current drops to only
16µA. In addition to the low quiescent current the LT1529
incorporates several protection features which make it
ideal for use in battery-powered systems. The device is
protected against reverse input voltages. In battery backup
applications where the output can be held up by a backup
battery when the input is pulled to ground, the LT1529 acts
like it has a diode in series with its output and prevents
reverse current flow.
Adjustable Operation
The adjustable version of the LT1529 has an output
voltage range of 3.75V to 14V. The output voltage is set
by the ratio of two external resistors as shown in Figure 2.
The device servos the output voltage to maintain the
voltage at the ADJ pin at 3.75V. The current in R1 is then
equal to 3.75V/R1. The current in R2 is equal to the sum
of the current in R1 and the ADJ pin bias current. The ADJ
pin bias current, 150nA at 25°C, flows through R2 into the
ADJ pin. The output voltage can be calculated according
to the formula in Figure 2. The value of R1 should be less
than 400k to minimize errors in the output voltage caused
by the ADJ pin bias current. Note that in shutdown the
output is turned off and the divider current will be zero.
Curves of ADJ Pin Voltage vs Temperature and ADJ Pin
8
include a bypass capacitor in battery-powered circuits. A
bypass capacitor in the range of 1µF to 10µF is sufficient.
The LT1529 is designed to withstand reverse voltages on
the V
pin with respect to ground and OUTPUT pin. In the
IN
case of a reversed input, which can happen if a battery is
plugged in backwards, the LT1529 will act as if there is a
diode in series with its input. There will be no reverse
current flow into the LT1529 and no reverse voltage will
appear at the load. The device will protect both itself and
the load.
W
U
Bias Current vs Temperature appear in the Typical Perfor-
mance Characteristics. The reference voltage at the ADJ
pin has a positive temperature coefficient of approxi-
mately 15ppm/°C. The ADJ pin bias current has a negative
temperature coefficient. These effects will tend to cancel
each other.
The adjustable device is specified with the ADJ pin tied to
the OUTPUT pin. This sets the output voltage to 3.75V.
Specifications for output voltage greater than 3.75V will be
proportional to the ratio of the desired output voltage to
3.75V (V
OUT
output current change of 1mA to 3A is – 0.5mV typical at
V
= 3.75V. At V
OUT
12
V
3 75
.
V
5
1
V
V
OUTPUT
OUT
IN
+
LT1529
V
R2
IN
4
2
SHDN
SENSE
GND
R1
3
LT1529 • F02
( )
1 + R2
V
= 3.75V
+ (I
× R2)
OUT
ADJ
R1
V
= 3.75V
ADJ
I
= 150nA AT 25°C
ADJ
OUTPUT RANGE = 3.3V TO 14V
Figure 2. Adjustable Operation
/3.75V). For example: load regulation for an
= 12V, load regulation would be:
OUT
(
)
(
)
– .
0 5
mV
– .
1 6
mV
=
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