LT1076_15 Datasheet, PDF (4/16 Pages) Linear Technology – Step-Down Switching Regulator

LT1074/LT1076
ELECTRICAL CHARACTERISTICS
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: To calculate maximum switch “on” voltage at currents between
low and high conditions, a linear interpolation may be used.
Note 3: A feedback pin voltage (V_FB) of 2.5V forces the V_C pin to its low
clamp level and the switch duty cycle to zero. This approximates the zero
load condition where duty cycle approaches zero.
Note 4: Total voltage from V_IN pin to ground pin must be ≥ 8V after start-
up for proper regulation.
Note 5: Switch frequency is internally scaled down when the feedback pin
voltage is less than 1.3V to avoid extremely short switch on times. During
testing, V_FB is adjusted to give a minimum switch on time of 1µs.
Note
6:
I_LIM
≈
R_LIM –
2k
1k
(LT1074),
I_LIM ≈
R_LIM – 1k
5.5k
(LT1076).
Note 7: Switch to input voltage limitation must also be observed.
Note 8: V_MAX = 40V for the LT1074/76 and 60V for the LT1074HV/76HV.
Note 9: Does not include switch leakage.
BLOCK DIAGRA
INPUT SUPPLY
LT1074
10µ A
0.3V
+
µ-POWER
SHUTDOWN
–
6V
REGULATOR
AND BIAS
320 µA
6V TO ALL
CIRCUITRY
2.35V
+
CURRENT
LIMIT
SHUTDOWN
500 Ω
CURRENT
LIMIT
COMP
+
0.04
C2
–
250 Ω
–
SHUTDOWN*
I _LIM*
4.5V 10k
4
2.21V
+
A1
ERROR
AMP
–
FREQ SHIFT
100kHz
OSCILLATOR
SYNC
3V(p-p)
R
S
R/S
LATCH
Q
G1
R
V_IN
Z
ANALOG
X
MULTIPLIER
XY
Z
Y
+
C1
–
PULSE WIDTH
COMPARATOR
FB
V_C
24V (EQUIVALENT)
LT1076
*AVAILABLE ON PACKAGES WITH PIN
COUNTS GREATER THAN 5.
0.1 Ω
400 Ω 15 Ω
SWITCH
OUTPUT
(V_SW)
100Ω
SWITCH
OUTPUT (V_SW )
LT1074 • BD01
sn1074 1074fds