SC8863-250CSKTR SEMTECH [Semtech Corporation], SC8863-250CSKTR Datasheet - Page 7

• Manufacturer Part Number: SC8863-250CSKTR
• Description: 150mA Ultra Low Dropout, Low Noise Regulator
• Manufacturer: SEMTECH [Semtech Corporation]

Theory Of Operation
The SC8863 is intended for applications where very low
dropout voltage, low supply current and low output noise
are critical. It provides a very simple, low cost solution
that uses very little pcb real estate. Fixed output voltage
options require the use of only two external capacitors
for operation.
Each voltage option has both fixed and adjustable
output voltage modes. Grounding the SET pin (pulling it
below the Sense/Select threshold of 55mV) will connect
the internal resistor divider to the error amplifier
resulting with the internally preset output voltage. If SET
is pulled above this threshold, then the Sense/Select
switch will connect the SET pin to the error amplifier. The
output will be regulated such that the voltage at SET will
equal V
An active high enable pin (EN) is provided to allow the
customer to shut down the part and enter an extremely
low power Off-state. A logic Low signal will reduce the
supply current to 0.1nA.
Component Selection - General
Output capacitor: Semtech recommends a minimum
capacitance of 1µF at the output with an equivalent
series resistance (ESR) of <1
Ceramic capacitors are ideal for this application.
Increasing the bulk capacitance will further reduce
POWER MANAGEMENT
Typical Characteristics (Cont.)
Applications Information
2005 Semtech Corp.
80
70
60
50
40
30
20
-50
VIN = 3.6V
SET
, the SET reference voltage (typically 1.250V).
-25
Sense/Select Threshold vs.
Junction Temperature
0
25
T
J
(°C)
50
over temperature.
75
100
125
7
output noise and improve the overall transient response.
Input capacitor: Semtech recommends the use of a 1µF
ceramic capacitor at the input. This allows for the device
being some distance from any bulk capacitance on the
rail. Additionally, input droop due to load transients is
reduced, improving load transient response.
Component Selection - Externally Set Output
Please refer to Figure 1 below. The output voltage can
be externally adjusted anywhere within the range from
1.25V to (V
accordance with the following equation:
V
OUT
0.01
0.1
=
10
C1
1uF Ceramic
1
. 1
0.1
250
IN(MIN)
Output Spectral Noise Density
Figure 1: Externally set output
•



1
+
3
1
- V
R
R
IN
EN
U1
1
2
D(MAX)
vs. Frequency



GND
2
1
SC8863
). The output voltage will be in
OUT
SET
f (kHz)
4
5
10
R1
R2
10k
SC8863
www.semtech.com
C
SC8863-2.8
VIN = 3.6V
I
T
OUT
OUT
C
J
OUT
= 25°C
= 100µF
= 50mA
C2
2.2uF Ceramic
= 1µF
100