LT3050EDDB#PBF Linear Technology, LT3050EDDB#PBF Datasheet - Page 18

• Manufacturer Part Number: LT3050EDDB#PBF
• Description: IC ADJ LDO REG 0.6V TO 44.5V 0.1A DFN-12
• Manufacturer: Linear Technology

Specifications of LT3050EDDB#PBF

• Primary Input Voltage: 45V
• Output Voltage Adjustable Range: 0.6V To 44.5V
• Dropout Voltage Vdo: 340mV
• No. Of Pins: 12
• Output Current: 100mA
• Operating Temperature Range: -40°C To +125°C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

LT3050 Series
APPLICATIONS INFORMATION
Table 1 shows 1% resistor divider values for some common
output voltages with a resistor divider current of 5μA.
Table 1. Output Voltage Resistor Divider Valves
Bypass Capacitance, Output Voltage Noise and
Transient Response
The LT3050 regulator provides low output voltage noise
over the 10Hz to 100kHz bandwidth while operating at
full load with the addition of a reference bypass capacitor
(C
low leakage capacitor is recommended. This capacitor will
bypass the internal reference of the regulator, providing a
low frequency noise pole. With the use of 10nF for C
the output voltage noise decreases to as low as 30μV
when the output voltage is set for 0.6V. For higher output
voltages (generated by using a feedback resistor divider),
the output voltage noise gains up accordingly when using
C
To lower the output voltage noise for higher output voltages,
include a feedforward capacitor (C
ADJ pin. A good quality, low leakage capacitor is recom-
mended. This capacitor will bypass the error amplifi er of
the regulator, providing a low frequency noise pole. With
the use of 10nF for both C
noise decreases to 30μV
set to 5V by a 5μA feedback resistor divider. If the current
in the feedback resistor divider is doubled, C
be doubled to achieve equivalent noise performance.
Higher values of output voltage noise are often measured if
care is not exercised with regard to circuit layout and test-
ing. Crosstalk from nearby traces induces unwanted noise
onto the LT3050’s output. Power supply ripple rejection
must also be considered. The LT3050 regulator does not
have unlimited power supply rejection and passes a small
portion of the input noise through to the output.
18
REF/BYP
REF/BYP
V
OUT
2.5
3.3
1.2
1.5
1.8
3
5
by itself.
) from the REF/BYP pin to GND. A good quality,
(V)
RMS
R1 (kΩ)
FF
118
121
124
115
124
124
115
and C
when the output voltage is
REF/BYP
FF
) from V
, output voltage
R2 (kΩ)
FF
365
499
562
845
118
182
249
OUT
must also
REF/BYP,
to the
RMS
Using a feedforward capacitor (C
pin has the added benefi t of improving transient response
for output voltages greater than 0.6V. With no feedforward
capacitor, the settling time will increase as the output
voltage is raised above 0.6V. Use the equation in Figure 2
to determine the minimum value of C
transient response that is similar to 0.6V output voltage
performance regardless of the chosen output voltage
(See Figure 3 and Transient Response in the Typical Perf-
ormance Characteristics section).
During start-up, the internal reference will soft-start if a
reference bypass capacitor is present. Regulator start-
up time is directly proportional to the size of the bypass
capacitor, slowing to 6ms with a 10nF bypass capacitor
(See Start-up Time vs REF/BYP Capacitor in the Typical
Performance Characteristics section). The reference by-
pass capacitor is actively pulled low during shutdown to
reset the internal reference.
Figure 2. Feedforward Capacitor for Fast Transient Response
LOAD CURRENT
Figure 3. Transient Response vs Feedforward Capacitor
V
100mA/DIV
IN
100pF
10nF
1nF
SHDN
IN
GND REF/BYP
0
LT3050-5
OUT
ADJ
C
REF/BYP
3050 F02
100μs/DIV
C
FF
C
I
FB DIVIDER
FF
10nF
10μA
FF
C
) from V
V
OUT
=
OUT
• I
R1+R2
(
V
FB DIVIDER
OUT
3050 F03
FF
(
10μA FOR FIXED V
OUT
V
C
I
FB-DIVIDER
to achieve a
OUT
OUT
)
to the ADJ
= 5V
= 10μF
= 10μA
3050fa
OUT
)