LT1965EDD-2.5#PBF Linear Technology, LT1965EDD-2.5#PBF Datasheet - Page 12

• Manufacturer Part Number: LT1965EDD-2.5#PBF
• Description: IC REG LDO 2.5V 1.1A 8-DFN
• Manufacturer: Linear Technology

Specifications of LT1965EDD-2.5#PBF

• Regulator Topology: Positive Fixed
• Voltage - Output: 2.5V
• Voltage - Input: Up to 20V
• Voltage - Dropout (typical): 0.31V @ 1.1A
• Number Of Regulators: 1
• Current - Output: 1.1A
• Current - Limit (min): 1.2A
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 8-DFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPLICATIONS INFORMATION
LT1965 Series
The LT1965 series are 1.1A low dropout regulators with
shutdown. The devices are capable of supplying 1.1A at
a typical dropout voltage of 310mV. The low operating
quiescent current (500μA for the adjustable version, 600μA
for the fi xed voltage versions) drops to less than 1μA in
shutdown. In addition to the low quiescent current, the
LT1965 regulators incorporate several protection features
that makes them ideal for use in battery-powered systems.
The devices protect themselves against both reverse input
and reverse output voltages. In battery backup applications,
if a backup battery holds up the output when the input is
pulled to ground, the LT1965 performs like it has a diode
in series with its output, preventing reverse current fl ow.
Also, in dual supply applications where the regulator load
is returned to a negative supply, the output can be pulled
below ground by as much as 20V. The LT1965 still starts
and operates normally in this situation.
Adjustable Operation
The LT1965 adjustable version has an output voltage range
of 1.20V to 19.5V. Figure 2 illustrates that the ratio of two
external resistors sets the output voltage. The device ser-
vos the output to maintain the ADJ pin voltage at 1.20V
referenced to ground. R1’s current equals 1.20V/R1. R2’s
current equals R1’s current plus the ADJ pin bias current.
The ADJ pin bias current, 1.3μA at 25°C, fl ows through
R2 into the ADJ pin. Use the formula in Figure 2 to calcu-
late output voltage. Linear Technology recommends that
R1’s value be less than 12.1k to minimize output voltage
errors due to the ADJ pin bias current. In shutdown, the
output turns off and the divider current is zero. For curves
depicting ADJ Pin Voltage vs Temperature and ADJ Pin
Bias Current vs Temperature, see the Typical Performance
Characteristics section.
12
V
IN
IN
LT1965
GND
OUT
1965 F02
ADJ
Figure 2. Adjustable Operation
R2
R1
+
V
OUT
I
OUTPUT RANGE = 1.20V TO 19.5V
V
V
ADJ
OUT
ADJ
= 1.3µA AT 25ºC
= 1.20V
= 1.20V 1+
R2
R1
+I
ADJ
• R2
The adjustable device is tested and specifi ed with the ADJ
pin tied to the OUT pin for an output voltage of 1.20V.
Specifi cations for output voltages greater than 1.20V are
proportional to the ratio of the desired output voltage to
1.20V: V
output current change of 1mA to 1.1A is typically –4.25mV
at V
Output Capacitance
The LT1965’s design is stable with a wide range of out-
put capacitors. The ESR of the output capacitor affects
stability, most notably with small capacitors. A minimum
output capacitor of 10μF with an ESR of 3Ω or less is
recommended to prevent oscillations. The LT1965 is a
low quiescent current device and output load transient
response is a function of output capacitance. Larger values
of output capacitance decrease the peak deviations and
provide improved transient response for larger current
changes.
Ceramic capacitors require extra consideration. Manufac-
turers make ceramic capacitors with a variety of dielectrics,
each with different behavior across temperature and applied
voltage. The most common dielectrics used are specifi ed
with EIA temperature characteristic codes of Z5U, Y5V,
X5R and X7R. The Z5U and Y5V dielectrics provide high
C-V products in a small package at low cost, but exhibit
strong voltage and temperature coeffi cients as shown in
Figures 3 and 4. When used with a 5V regulator, a 16V
10μF Y5V capacitor can exhibit an effective value as low
as 1μF to 2μF for the DC bias applied and over the operat-
ing temperature range. The X5R and X7R dielectrics yield
much more stable characteristics and are more suitable
for use as the output capacitor. The X7R type works over
a wider temperature range and has better temperature
stability whereas X5R is less expensive and is available in
higher values. Care still must be exercised when using X5R
and X7R capacitors; the X5R and X7R codes only specify
operating temperature range and maximum capacitance
change over temperature. Capacitance change due to DC
bias with X5R and X7R capacitors is better than Y5V and
Z5U capacitors, but can still be signifi cant enough to drop
1.20V
OUT
5V
= 1.20V. At V
OUT
• –4.25mV = –17.71mV
/1.20V. For example, load regulation for an
OUT
= 5V, load regulation is:
1965fa