LTC3026EMSE-1#PBF Linear Technology, LTC3026EMSE-1#PBF Datasheet - Page 10

• Manufacturer Part Number: LTC3026EMSE-1#PBF
• Description: 1.5a vldo in dfn... ic reg ldo adj 1.5a...
• Manufacturer: Linear Technology

operaTion
LTC3026
The LDO provides a high accuracy output capable of
supplying 1.5A of output current with a typical dropout
voltage of only 100mV. A single ceramic capacitor as
small as 10µF is all that is required for output bypassing.
A low reference voltage allows the LTC3026 output to be
programmed to much lower voltages than available in
common LDOs (range of 0.4V to 2.6V).
The devices also include current limit and thermal overload
protection, and will survive an output short-circuit indefi-
nitely. The fast transient response of the follower output
stage overcomes the traditional trade-off between dropout
voltage, quiescent current and load transient response
inherent in most LDO regulator architectures, see Figure 1.
The LTC3026 also includes a soft-start feature to prevent
excessive current flow at V
LDO is enabled, the soft-start circuitry gradually increases
the LDO reference voltage from 0V to 0.4V over a period
of approximately 200µs, see Figure 2.
10
AC 20mV/DIV
I
OUT
1.5A
0mA
OUT
Figure 1. Output Load Step Response
V
C
V
V
OUT
OUT
IN
B
= 5V
= 1.7V
= 1.5V
= 10µF
100µs/DIV
IN
during start-up. When the
3026 F01
Adjustable Output Voltage
The output voltage is set by the ratio of two external resis-
tors as shown in Figure 3. The device servos the output
to maintain the ADJ pin voltage at 0.4V (referenced to
ground). Thus, the current in R1 is equal to 0.4V/R1. For
good transient response, stability and accuracy the current
in R1 should be at least 80µA, thus, the value of R1 should
be no greater than 5k. The current in R2 is the current in
R1 plus the ADJ pin bias current. Since the ADJ pin bias
current is typically <10nA it can be ignored in the output
voltage calculation. The output voltage can be calculated
using the formula in Figure 3. Note that in shutdown the
output is turned off and the divider current will be zero
once C
OUT
SHDN
OUT
PG
is discharged.
1.5V
1.5V
Figure 2. Soft-Start with Boost Disable
LTC3026
LO
HI
0V
0V
Figure 3. Programming the LTC3026
T
R
V
V
A
IN
B
OUT
= 25°C
= 5V
= 1.7V
V
GND
ADJ
OUT
= 1
R2
R1
100µs/DIV
C
OUT
V
OUT
= 0.4V 1+
3026 F02

 
3026 F03
R2
R1

 
3026ff