LT1766IFE-5-PBF LINER [Linear Technology], LT1766IFE-5-PBF Datasheet - Page 9

• Manufacturer Part Number: LT1766IFE-5-PBF
• Description: 5.5V to 60V 1.5A, 200kHz Step-Down Switching Regulator
• Manufacturer: LINER [Linear Technology]

BLOCK DIAGRAM
will have 90° phase shift at a much lower frequency, but
will not have the additional 90° shift until well beyond
the LC resonant frequency. This makes it much easier to
frequency compensate the feedback loop and also gives
much quicker transient response.
Most of the circuitry of the LT1766 operates from an internal
2.9V bias line. The bias regulator normally draws power
from the regulator input pin, but if the BIAS pin is connected
to an external voltage higher than 3V, bias power will be
drawn from the external source (typically the regulated
SHDN 15
SYNC
BIAS
V
IN
COMPARATOR
10
14
4
SHUTDOWN
REGULATOR
+
2.9V BIAS
2.38V
0.4V
–
+
–
COMPARATOR
LOCKOUT
5.5μA
INTERNAL
V
CC
ANTISLOPE COMP
SLOPE COMP
OSCILLATOR
200kHz
Figure 1. LT1766 Block Diagram
V
CLAMP
C(MAX)
∑
Q3
+
output voltage). This will improve effi ciency if the BIAS
pin voltage is lower than regulator input voltage.
High switch effi ciency is attained by using the BOOST
pin to provide a voltage to the switch driver which is
higher than the input voltage, allowing switch to be satu-
rated. This boosted voltage is generated with an external
capacitor and diode. Two comparators are connected to the
shutdown pin. One has a 2.38V threshold for undervoltage
lockout and the second has a 0.4V threshold for complete
shutdown.
×1
11
V
R
C
LIMIT
FOLDBACK
CURRENT
–
CLAMP
LIMIT
CURRENT
COMPARATOR
Q2
S
R
FLIP-FLOP
R
g
m
S
FREQUENCY
= 2000μMho
FOLDBACK
AMPLIFIER
ERROR
LT1766/LT1766-5
BOOST
CIRCUITRY
6
DRIVER
–
+
1.22V
1766 F01
12
2
Q1
POWER
SWITCH
R
SENSE
FB
GND
1, 8, 9, 16, 17
SW
1766fc
9