LT1963EST-1.5#PBF Linear Technology, LT1963EST-1.5#PBF Datasheet - Page 15

• Manufacturer Part Number: LT1963EST-1.5#PBF
• Description: IC REG LDO 1.5V 1.5A LN SOT223-3
• Manufacturer: Linear Technology

Specifications of LT1963EST-1.5#PBF

• Regulator Topology: Positive Fixed
• Voltage - Output: 1.5V
• Voltage - Input: 2.1 ~ 20 V
• Voltage - Dropout (typical): 0.34V @ 1.5A
• Number Of Regulators: 1
• Current - Output: 1.5A
• Current - Limit (min): 1.6A
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: SOT-223 (3 leads + Tab), SC-73, TO-261
• Primary Input Voltage: 2.5V
• Output Voltage Fixed: 1.5V
• Dropout Voltage Vdo: 340mV
• No. Of Pins: 3
• Output Current: 1.5A
• Voltage Regulator Case Style: SOT-223
• Operating Temperature Range: -40°C To
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPLICATIONS INFORMATION
Table 1. Capacitor Minimum ESR
Figures 3 through 8 show the effect of ESR on the transient
response of the regulator. These scope photos show the
transient response for the LT1963A at three different output
voltages with various capacitors and various values of ESR.
The output load conditions are the same for all traces. In
all cases there is a DC load of 500mA. The load steps up
to 1A at the fi rst transition and steps back to 500mA at
the second transition.
At the worst case point of 1.2V
(Figure 3), a minimum amount of ESR is required. While
20mΩ is enough to eliminate most of the ringing, a value
closer to 50mΩ provides a more optimum response. At
2.5V output with 10μF C
at the transitions with 0Ω ESR but still settles to within
10mV in 20μs after the 0.5A load step. Once again a small
value of ESR will provide a more optimum response.
At 5V
damped with 0Ω ESR.
With a C
(Figure 6), the output rings although the amplitude is
only 20mV
20mΩ of ESR to provide good damping at 1.2V output.
Performance at 2.5V and 5V output with 100μF C
similar characteristics to the 10μF case (see Figures 7-8).
At 2.5V
At 5V
Capacitor types with inherently higher ESR can be combined
with 0mΩ ESR ceramic capacitors to achieve both good
high frequency bypassing and fast settling time. Figure
9 illustrates the improvement in transient response that
can be seen when a parallel combination of ceramic and
V
1.2V
1.5V
1.8V
2.5V
3.3V
≥5V
OUT
OUT
OUT
OUT
OUT
the response is well damped with 0Ω ESR.
with 10μF C
5mΩ to 20mΩ can improve transient response.
p-p
of 100μF at 0Ω ESR and an output of 1.2V
. With C
20mΩ
20mΩ
15mΩ
10μF
5mΩ
0mΩ
0mΩ
OUT
OUT
OUT
15mΩ
15mΩ
10mΩ
(Figure 5) the response is well
22μF
of 100μF it takes only 5mΩ to
5mΩ
0mΩ
0mΩ
(Figure 4) the output rings
OUT
10mΩ
10mΩ
10mΩ
47μF
5mΩ
0mΩ
0mΩ
with 10μF C
OUT
100μF
5mΩ
5mΩ
5mΩ
5mΩ
5mΩ
0mΩ
shows
OUT
POSCAP capacitors are used. The output voltage is at the
worst case value of 1.2V. Trace A, is with a 10μF ceramic
output capacitor and shows signifi cant ringing with a peak
amplitude of 25mV. For Trace B, a 22μF/45mΩ POSCAP is
added in parallel with the 10μF ceramic. The output is well
damped and settles to within 10mV in less than 20μs.
For Trace C, a 100μF/35mΩ POSCAP is connected in
parallel with the 10μF ceramic capacitor. In this case the
peak output deviation is less than 20mV and the output
settles in about 10μs. For improved transient response
the value of the bulk capacitor (tantalum or aluminum
electrolytic) should be greater than twice the value of the
ceramic capacitor.
Tantalum and Polytantalum Capacitors
There is a variety of tantalum capacitor types available,
with a wide range of ESR specifi cations. Older types have
ESR specifi cations in the hundreds of mΩ to several Ohms.
Some newer types of polytantalum with multi-electrodes
have maximum ESR specifi cations as low as 5mΩ. In gen-
eral the lower the ESR specifi cation, the larger the size and
the higher the price. Polytantalum capacitors have better
surge capability than older types and generally lower ESR.
Some types such as the Sanyo TPE and TPB series have
ESR specifi cations in the 20mΩ to 50mΩ range, which
provide near optimum transient response.
Aluminum Electrolytic Capacitors
Aluminum electrolytic capacitors can also be used with the
LT1963A. These capacitors can also be used in conjunction
with ceramic capacitors. These tend to be the cheapest and
lowest performance type of capacitors. Care must be used
in selecting these capacitors as some types can have ESR
which can easily exceed the 3Ω maximum value.
Ceramic Capacitors
Extra consideration must be given to the use of ceramic
capacitors. Ceramic capacitors are manufactured with a
variety of dielectrics, each with different behavior over
temperature and applied voltage. The most common
dielectrics used are Z5U, Y5V, X5R and X7R. The Z5U and
LT1963A Series
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