LTC1436AIGN Linear Technology, LTC1436AIGN Datasheet - Page 16

• Manufacturer Part Number: LTC1436AIGN
• Description: IC SW REG SYNC STEP-DOWN 24-SSOP
• Manufacturer: Linear Technology
• Type: Step-Down (Buck)r

Specifications of LTC1436AIGN

• Internal Switch(s): No
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 1.19 ~ 9 V
• Current - Output: 50mA
• Frequency - Switching: 125kHz ~ 240kHz
• Voltage - Input: 3.5 ~ 30 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 24-SSOP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Power - Output: -

APPLICATIONS
LTC1436A
LTC1436-PLL-A/LTC1437A
Topside MOSFET Driver Supply (C
An external bootstrap capacitor C
pin supplies the gate drive voltage for the topside
MOSFET(s). Capacitor C
charged through diode D
is low. When one of the topside MOSFET(s) is to be turned
on, the driver places the C
of the desired MOSFET. This enhances the MOSFET and
turns on the topside switch. The switch node voltage SW
rises to V
value of the boost capacitor C
greater than the total input capacitance of the topside
MOSFET(s). In most applications 0.1µF is adequate. The
reverse breakdown on D
Output Voltage Programming
The output voltage is pin selectable for all members of the
LTC1436A/LTC1437A family. The output voltage is
selected by the V
The LTC1436A/LTC1437A family also has remote output
voltage sense capability. The top of an internal resistive
divider is connected to V
output voltage applications the V
to the output voltage as shown in Figure 5a. When using
an external resistive divider, the V
and the V
as shown in Figure 5b.
16
V
V
V
EXTV
LTC1436A
LTC1437A
PROG
PROG
PROG
CC
Figure 4b. Capacitive Charge Pump for EXT V
OSENSE
IN
= 0V
= INTV
= Open (DC)
PGND
TGL
TGS
SW
V
BG
and the Boost pin rises to V
IN
C
IN
pin is connected to the feedback resistors
CC
PROG
+
U
N-CH
pin as follows:
B
N-CH
N-CH
INFORMATION
B
B
B
U
OSENSE
must be greater than V
from INTV
voltage across the gate source
V
in the functional diagram is
IN
V
V
V
OUT
OUT
OUT
B
BAT85
PROG
B
. For fixed 3.3V and 5V
OSENSE
needs to be 100 times
L1
connected to the Boost
W
= 3.3V
= 5V
= Adjustable
B
, D
CC
+
pin is left open (DC)
B
R
when the SW pin
IN
VN2222LL
pin is connected
SENSE
)
1µF
0.22µF
+ INTV
U
+
CC
IN(MAX).
CC
BAT85
BAT85
C
1436 F04b
. The
OUT
Power-On Reset Function (POR)
The power-on reset function monitors the output voltage
and turns on an open drain device when it is out of
regulation. An external pull-up resistor is required on the
POR pin.
When power is first applied or when coming out of
shutdown, the POR output is pulled to ground. When the
output voltage rises above a level which is 5% below the
final regulated output value, an internal counter starts.
After counting 2
down device turns off.
The POR output will go low whenever the output voltage
drops below 7.5% of its regulated value for longer than
approximately 30µs, signaling an out-of-regulation condi-
tion. In shutdown, the POR output is pulled low even if the
regulator’s output is held up by an external source.
Run/Soft Start Function
The RUN/SS pin is a dual purpose pin that provides the
soft start function and a means to shut down the
LTC1436A/LTC1437A. Soft start reduces surge currents
from V
Power supply sequencing can also be accomplished
using this pin.
Figure 5a. LTC1436A/LTC1437A Fixed Output Applications
Figure 5b. LTC1436A/LTC1437A Adjustable Applications
IN
by gradually increasing the internal current limit.
V
LTC1436A
LTC1437A
LTC1436A
LTC1437A
OUT
= 1.19V 1 +
16
V
V
(65536) clock cycles, the POR pull-
OSENSE
( )
OSENSE
V
V
SGND
SGND
PROG
PROG
R2
R1
GND: V
INTV
OPEN (DC)
CC
+
OUT
: V
100pF
OUT
C
= 3.3V
1.19V ≤ V
OUT
= 5V
1436 F05a
OUT
R2
R1
V
OUT
≤ 9V
1436 F05b
14367afb