LTC1625IGN#TR Linear Technology, LTC1625IGN#TR Datasheet - Page 14

• Manufacturer Part Number: LTC1625IGN#TR
• Description: IC SW REG STEP-DOWN SYNC 16-SSOP
• Manufacturer: Linear Technology
• Type: Step-Down (Buck)r

Specifications of LTC1625IGN#TR

• Internal Switch(s): No
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 1.19 ~ 36 V
• Current - Output: 50mA
• Frequency - Switching: 150kHz
• Voltage - Input: 3.7 ~ 36 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-SSOP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Power - Output: -
• Other names: LTC1625IGNTR; Q1127755

APPLICATIONS
LTC1625
Note that R
gate drives other than the 5.2V INTV
be accounted for when selecting the MOSFET R
Particular care should be taken with applications where
EXTV
voltage is between 4.7V and 5.2V, INTV
nected to the output and the gate drive is reduced. The
resulting increase in R
limit. Even applications with V
region during start-up and must take into account the
reduced current limit.
Topside MOSFET Driver Supply (C
An external bootstrap capacitor (C
diagram) connected to the BOOST pin supplies the gate
drive voltage for the topside MOSFET. This capacitor is
charged through diode D
is low. Note that the voltage across C
drop below INTV
switch node voltage rises to V
to approximately V
C
refreshes. Thus, the boost capacitance needs to store
about 100 times the gate charge required by the top
MOSFET. In many applications 0.22 F is adequate.
When adjusting the gate drive level , the final arbiter is the
total input current for the regulator. If you make a change
and the input current decreases, then you improved the
efficiency. If there is no change in input current, then there
is no change in efficiency.
Output Voltage Programming
The LTC1625 has a pin selectable output voltage deter-
mined by the V
V
V
V
Remote sensing of the output voltage is provided by the
V
internal resistive divider is used and the V
connected directly to the output voltage as shown in
Figure 6a. When using an external resistive divider, the
14
B
PROG
PROG
PROG
OSENSE
supplies the top driver for as long as ten cycles between
CC
= 0V
= INTV
= Open
pin. For fixed 3.3V and 5V output applications an
is connected to the output. When the output
DS(ON)
CC
PROG
CC
also varies with the gate drive level. If
IN
. When the top MOSFET turns on, the
U
pin as follows:
+ INTV
DS(ON)
B
INFORMATION
from INTV
U
CC
V
V
V
OUT
. During dropout operation,
OUT
OUT
OUT
IN
will also lower the current
and the BOOST pin rises
> 5.2V will traverse this
= 3.3V
= 5V
= Adjustable
W
CC
B
CC
, D
B
are used, this must
B
when the SW node
in the functional
B
is about a diode
)
CC
OSENSE
will be con-
U
DS(ON)
pin is
.
V
feedback resistors as shown in Figure 6b. The output
voltage is set by the divider as:
Run/Soft Start Function
The RUN/SS pin is a dual purpose pin that provides a soft
start function and a means to shut down the LTC1625. Soft
start reduces surge currents from V
creasing the controller’s current limit I
can also be used for power supply sequencing.
Pulling the RUN/SS pin below 1.4V puts the LTC1625 into
a low quiescent current shutdown (I
be driven directly from logic as shown in Figure 7. Releas-
ing the RUN/SS pin allows an internal 3 A current source
to charge up the external capacitor C
been pulled all the way to ground there is a delay before
starting of approximately:
PROG
V
OUT
pin is left open and the V
1 19 1
V
.
OUT
+
V
OUT
Figure 6a. Fixed 3.3V or 5V V
= 3.3V:
V
C
= 5V: INTV
Figure 6b. Adjustable V
V
OUT
OUT
R
R
GND
R2
R1
2
CC
1
+
OPEN
C
OUT
OSENSE
V
V
SGND
V
V
SGND
PROG
OSENSE
PROG
OSENSE
Q
LTC1625
LTC1625
< 30 A). This pin can
OUT
IN
pin is connected to
SS
TH(MAX)
OUT
1625 F06b
by gradually in-
. If RUN/SS has
1625 F06a
. This pin