LT3150CGN#PBF Linear Technology, LT3150CGN#PBF Datasheet - Page 12

• Manufacturer Part Number: LT3150CGN#PBF
• Description: IC CTRLR REG VLDO FET 16-SSOP
• Manufacturer: Linear Technology
• Type: Positive Adjustabler

Specifications of LT3150CGN#PBF

• Number Of Outputs: 1
• Voltage - Output: 2.5 ~ 18.4 V
• Current - Supply: 12mA
• Voltage - Input: 1.5 ~ 10 V, 10 ~ 20 V
• Operating Temperature: 0°C ~ 70°C
• Package / Case: 16-SSOP
• Primary Input Voltage: 10V
• Dropout Voltage Vdo: 130mV
• No. Of Pins: 16
• Output Current: 10A
• Operating Temperature Range: 0°C To +70°C
• Msl: MSL 1 - Unlimited
• Output Voltage Adjustable Min, Vout: 1.5V
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPLICATIO S I FOR ATIO
LT3150
holds internal comparator COMP3’s output low. This
comparator circuit, now enabled, monitors the GATE pin
and detects saturation at the positive rail. When a saturated
condition is detected, COMP3 activates the shutdown timer.
Once the time-out period occurs, the output is shut down
and latched off. The operation of resetting the latch remains
the same. Note that this technique does not limit the FET
current during the time-out period. The output current is
only limited by the input power supply and the input/out-
put impedance. Setting the timer to a short period in this
mode of operation keeps the external MOSFET within its
SOA (safe operating area) boundary and keeps the
MOSFET’s temperature rise under control.
Unique circuit design incorporated into the LT3150 allevi-
ates all concerns about power supply sequencing. The
issue of power supply sequencing is an important topic as
the typical LT3150 application has two separate power
supply inputs, V
slow in ramping up or is held off by SHDN1, insufficient
MOSFET gate drive exists and therefore, the output
voltage does not come up. This statement is true as long
as the V
external MOSFET. Prior to the boost converter powering
up, V
through the boost inductor. If V
MOSFET turns on and pulls the output voltage up. If this
situation exists and the output must be held off, then
pulling the SHDN2 pin high actively holds the output off.
Pull the SHDN2 pin low to allow start-up, as the SHDN2
high logic state is a latched condition.
If V
I
to drive the GATE pin to the positive V
in a large current as the V
undervoltage lockout circuit COMP2, which monitors the
I
low until the I
internal 1.21 reference voltage. The undervoltage lockout
circuit then smoothly releases the COMP pin and allows
the output voltage to come up in dropout from the input
supply voltage. An additional benefit derived from the
speed of the LT3150 feedback loop is that turn-on
overshoot is virtually nonexistent in a properly compen-
sated system.
12
POS
POS
IN2
pin is slow in ramping, then the feedback loop wants
supply voltage, holds Q6 on and pulls the COMP pin
IN2
is present, but the V
IN1
equals V
input voltage is lower than the threshold of the
POS
IN1
IN1
voltage increases to greater than the
U
and V
– V
IN2
IN1
U
F
IN1
due to the DC path present
. If the V
supply ramps up. However,
supply voltage tied to the
IN1
W
IN2
is high enough, the
IN2
supply voltage is
rail. This results
U
BOOST REGULATOR COMPONENT SELECTION
Diode
Linear Technology recommends the use of a Schottky
diode with the LT3150. For input supply voltages less than
2V, the Motorola MBR0520 or equivalent is a good choice
due to its small size, low cost and low forward voltage. The
average diode current equals the V
12mA typically. The peak diode current equals the peak
switch current, which in these low input-to-output voltage
applications ranges from 100mA to 200mA.
The diode’s forward voltage during its conduction period
directly affects the duty cycle of the boost converter. These
low input-to-output voltage applications require the boost
converter to operate at duty cycles close to the maximum
and the difference of a few hundred millivolts in the diode
forward voltage results in a duty cycle difference of several
percent. For supply voltages greater than 2V, a 1N4148 is
suitable and lowers cost.
Inductor
Use inductors with a saturation current rating (where
inductance is approximately 70% of zero current induc-
tance) of 0.2A or greater. Also, choose an inductor with a
DCR of 2.5 or less. The inductor’s DCR also affects the
boost converter’s duty cycle. A larger DCR value increases
the required duty cycle. An inductance value between
4.7 H and 10 H works well in most applications.
Table 1 lists several 10 H inductors that work with the
LT3150, although this is by no means an exhaustive list.
Many magnetic vendors have components suitable for use
in this boost application.
Input Capacitor
The input bypass capacitors serve as the reservoir capaci-
tor for the boost regulator, the linear regulator and what-
ever other system circuitry the input supply powers.
Therefore, the input capacitor network is most likely
distributed along the input supply PCB plane.
However, the switching of current at high speed by the
boost regulator mandates a local bypass capacitor at the
V
IN1
pin. Place this input capacitor physically close to the
IN2
supply current of
3150f