LT1082IQ#TRPBF Linear Technology, LT1082IQ#TRPBF Datasheet - Page 7

• Manufacturer Part Number: LT1082IQ#TRPBF
• Description: IC SWTCHNG REG HI-V/EFF 1A 5-DD
• Manufacturer: Linear Technology
• Type: Step-Down (Buck), Step-Up (Boost), Inverting, Flyback, Forward Converterr

Specifications of LT1082IQ#TRPBF

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Current - Output: 1A
• Frequency - Switching: 60kHz
• Voltage - Input: 3 ~ 75 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: D²Pak, TO-263 (5 leads + tab)
• Power - Output: 20W
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Output: -

OPERATIO
BLOCK
The LT1082 is a current mode switcher. This means that
switch duty cycle is directly controlled by switch current
rather than by output voltage. Referring to the block
diagram, the switch is turned “on” at the start of each
oscillator cycle. It is turned “off” when switch current
reaches a predetermined level. Control of output voltage is
obtained by using the output of a voltage sensing error
amplifier to set current trip level. This technique has
several advantages. First, it has immediate response to
input voltage variations, unlike ordinary switchers which
have notoriously poor line transient response. Second, it
reduces the 90 phase shift at mid-frequencies in the
energy storage inductor. This greatly simplifies closed-
loop frequency compensation under widely varying input
voltage or output load conditions. Finally, it allows simple
pulse-by-pulse current limiting to provide maximum switch
protection under output overload or short conditions. A
I D AGRA
FB
U
W
MODE SELECT
60kHz
14kHz
1.24V
2.3V
REG
OSC
REF
V
IN
–
+
ERROR
AMP
SHUTDOWN
CIRCUIT
LOGIC
COMP
GND
0.15V
V
C
low dropout internal regulator provides a 2.3V supply for
all internal circuitry on the LT1082. This low dropout
design allows input voltage to vary from 3V to 75V with
virtually no change in device performance. A 60kHz
oscillator is the basic clock for all internal timing. It turns
“on” the output switch via the logic and driver circuitry.
Special adaptive anti-sat circuitry detects onset of
saturation in the power switch and adjusts driver current
instantaneously to limit switch saturation. This minimizes
driver dissipation and provides very rapid turn-off of the
switch.
A 1.2V bandgap reference biases the positive input of the
error amplifier. The negative input is brought out for
output voltage sensing. This feedback pin has a second
function: when pulled low with an external resistor and
with I
* ALWAYS CONNECT E1 TO GROUND PIN ON MiniDIP PACKAGE.
EMITTERS TIED TO GROUND ON TO-220 PACKAGE.
FLYBACK
ERROR
AMP
FB
of 60 A to 200 A, it programs the LT1082 to
GAIN 5
ANTI-SAT
DRIVER
CURRENT
AMP
16.2V
+
–
SWITCH OUT
0.2
E1* E2
0.2
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LT1082
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