LT3757MPMSE#PBF Linear Technology, LT3757MPMSE#PBF Datasheet - Page 11

• Manufacturer Part Number: LT3757MPMSE#PBF
• Description: IC DC-DC CTRLR ADJ 10MSOP
• Manufacturer: Linear Technology
• Type: Step-Up (Boost), Inverting, Flyback, Sepicr

Specifications of LT3757MPMSE#PBF

• Internal Switch(s): No
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Frequency - Switching: 100kHz ~ 1MHz
• Voltage - Input: 2.9 ~ 40 V
• Operating Temperature: -55°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 10-MSOP Exposed Pad, 10-HMSOP, 10-eMSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output: -
• Voltage - Output: -
• Power - Output: -

applicaTions inForMaTion
An effective approach to reduce the power consumption
of the internal LDO for gate drive is to tie the INTV
to an external voltage source high enough to turn off the
internal LDO regulator.
If the input voltage V
maximum rating of both the power MOSFET gate-source
voltage (V
voltage (17.5V), the INTV
to the V
turned off and the gate driver will be powered directly
from the input voltage, V
V
INTV
the lowest shutdown mode input supply current, do not
connect the INTV
In SEPIC or flyback applications, the INTV
connected to the output voltage V
diode, as shown in Figure 3, if V
conditions:
1. V
2. 7.2 < V
3. V
A resistor R
limit the inrush current from V
IN
Figure 2. Recommended Maximum Q
Frequencies to Ensure INTV
, however, a small current (around 16µA) will load the
CC
OUT
OUT
in shutdown mode. For applications that require
IN
GS
pin. In this condition, the internal LDO will be
< V
< maximum V
300
250
200
150
100
VCC
50
) and the INTV
0
OUT
0
IN
can be connected, as shown in Figure 3, to
< 17.5V
(pin voltage)
CC
5
pin to V
10
IN
IN
15
does not exceed the absolute
GS
CC
. With the INTV
CC
V
1MHz
CC
rating of power MOSFET
overvoltage lockout threshold
IN
300kHz
IN
20
pin can be shorted directly
(V)
Higher Than 4.5V
.
OUT
25
OUT
. Regardless of whether
OUT
30
G
meets the following
through a blocking
vs V
35
CC
IN
3757 F02
pin shorted to
CC
40
at Different
pin can be
CC
pin
or not the INTV
source, it is always necessary to have the driver circuitry
bypassed with a 4.7µF low ESR ceramic capacitor to ground
immediately adjacent to the INTV
Operating Frequency and Synchronization
The choice of operating frequency may be determined
by on-chip power dissipation, otherwise it is a trade-off
between efficiency and component size. Low frequency
operation improves efficiency by reducing gate drive cur-
rent and MOSFET and diode switching losses. However,
lower frequency operation requires a physically larger
inductor. Switching frequency also has implications for
loop compensation. The LT3757 uses a constant-frequency
architecture that can be programmed over a 100kHz to
1000kHz range with a single external resistor from the
RT pin to ground, as shown in Figure 1. The RT pin must
have an external resistor to GND for proper operation of
the LT3757. A table for selecting the value of R
operating frequency is shown in Table 1.
Table 1. Timing Resistor (R
OSCILLATOR FREQUENCY (kHz)
Figure 3. Connecting INTV
LT3757
1000
CC
100
200
300
400
500
600
700
800
900
INTV
GND
pin is connected to an external voltage
CC
T
) Value
3757 F03
C
4.7µF
VCC
D
VCC
CC
R
CC
VCC
and GND pins.
to V
V
OUT
OUT
R
LT3757
T
63.4
41.2
30.9
24.3
19.6
16.5
12.1
10.5
140
14
(kΩ)
T
for a given

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