sc1456aims.tr Semtech Corporation, sc1456aims.tr Datasheet - Page 8

• Manufacturer Part Number: sc1456aims.tr
• Description: Sc1456 Dual 150 Ma Ultra-low Dropout, Low Noise Regulator
• Manufacturer: Semtech Corporation

Theory Of Operation
The SC1456 is intended for applications where very low
dropout voltage, low supply current, low output noise and
pcb real estate are critical. It provides a very simple, low
cost solution for two seperate regulated outputs.
Internally preset output voltage options require the use
of only four external capacitors for operation.
Each regulator 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 of that regulator 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
voltage (typically 1.250V).
An active high enable pin (EN) is provided for each
output to allow the customer to shut down that
regulator and enter an extremely low power Off-state. A
logic Low signal will reduce the regulator’s supply current
to 0.1nA.
Component Selection - General
Output capacitor: Semtech recommends a minimum
capacitance of 1µF at each output with an equivalent
POWER MANAGEMENT
Typical Characteristics (Cont.)
Applications Information
2005 Semtech Corp.
80
70
60
50
40
30
20
-50
VIN = 3.6V
-25
Sense/Select Threshold vs.
Junction Temperature
0
25
T
J
(°C)
50
SET
, the SET reference
75
100
125
8
series resistance (ESR) of <1
Ceramic capacitors are ideal for this application.
Increasing the bulk capacitance will further reduce
output noise and improve the overall transient response.
Input capacitor: Semtech recommends the use of a 1µF
ceramic capacitor at each 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 on page 9. The output voltage of
both outputs (OUT1 shown here) can be externally
adjusted anywhere within the range from 1.25V to
(V
with the following equation:
1% tolerance resistors are recommended. The values of
R1 and R2 should be selected such that the current flow
through them is 10µA (thus R2
voltages and/or high output currents, stability may be
improved by increasing C2 to 2.2µF and reducing R2 to
10k . See “Component Selection - General” for input
capacitor requirements.
V
OUT
IN(MIN)
0.01
0.1
10
1
0.1
. 1
- V
250
D(MAX)
Output Spectral Noise Density
). The output voltage will be in accordance
1
R
R
1
2
vs. Frequency
1
f (kHz)
120k ). At high input
over temperature.
10
SC1456
www.semtech.com
C
SC1456B
VIN = 3.6V
I
T
OUT
OUT
C
J
OUT
= 25°C
= 100µF
= 50mA
= 1µF
100