lt3070 Linear Technology Corporation, lt3070 Datasheet - Page 23

• Manufacturer Part Number: lt3070
• Description: 5a, Low Noise, Programmable Output, 85mv Dropout Linear Regulator
• Manufacturer: Linear Technology Corporation

ApplicAtions inFormAtion
Table 4 shows a simple guideline for PCB trace resistance
as a function of weight and trace width.
Table 4. PC Board Trace Resistance
*Trace resistance is measured in milliohms/in
Quieting the Noise
The LT3070 offers numerous noise performance advan-
tages. Each LDO has several sources of noise. An LDO’s
most critical noise source is the reference, followed by
the LDO error amplifier. Traditional low noise regulators
buffer the voltage reference out to an external pin (usually
through a large value resistor) to allow for bypassing and
noise reduction of reference noise. The LT3070 deviates
WEIGHT (Oz)
1
2
100 MIL WIDTH*
5.43
2.71
1.5V
V
IN
2.5V TO 3.6V
V
BIAS
330µF
1nF
NC
NC
200 MIL WIDTH*
Figure 6. 1.5V to 1.2V Linear Regulator
IN
EN
V
V
V
MARGSEL
MARGTOL
VIOC
2.71
1.36
O0
O1
O2
2.2µF
LT3070
BIAS
GND
REF/BYP
PWRGD
SENSE
OUT
50k
from the traditional voltage reference by generating a
low voltage V
nal resistor ≅19k. This intermediate impedance node
(REF/BYP) facilitates external filtering directly. A 10nF filter
capacitor minimizes reference noise to 10µV
600mV REF/BYP pin, equivalently a 17µV contribution to
output noise at V
Characteristics for Noise vs Output Voltage performance
as a function of C
This approach also accommodates reference sharing
between LT3070 regulators that are hooked up in cur-
rent sharing applications. The REF/BYP filter capacitor
delays the initial power-up time by a factor of the RC time
constant. V
time is significantly reduced and well controlled coming
out of nap mode (EN:LO↑HI).
3070 F06
*X5R OR X7R CAPACITORS
0.01µF
2.2µF*
PWRGD
REF
4.7µF*
REF
remains active in nap mode, thus start-up
from a reference current into an inter-
OUT
REF/BYP
10µF*
= 1V. See the Typical Performance
.
V
1.2V
5A
OUT
LT3070
RMS

at the
3070f