Datasheet

LT1765/LT1765-1.8/LT1765-2.5/
LT1765-3.3/LT1765-5
3
1765fd
ELECTRICAL CHARACTERISTICS
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: The LT1765E is guaranteed to meet performance specifi cations
from 0°C to 125°C. Specifi cations over the –40°C to 125°C operating
junction temperature range are assured by design, characterization and
correlation with statistical process controls.
PARAMETER CONDITIONS MIN TYP MAX UNITS
Maximum Switch Current Limit 346 A
Oscillator Frequency 3.3V < V
IN
< 25V
l
1.1 1.25 1.6 MHz
Switch On Voltage Drop I = 3A
l
270 430 mV
V
IN
Undervoltage Lockout (Note 3)
l
2.47 2.6 2.73 V
V
IN
Supply Current
l
1 1.3 mA
Shutdown Supply Current V
SHDN
= 0V, V
IN
= 25V, V
SW
= 0V
l
15 35
55
μA
μA
Feedback Voltage 3V < V
IN
< 25V, 0.4V < V
C
< 0.9V
(Note 3)
LT1765 (Adj)
l
1.182
1.176
1.2 1.218
1.224
V
V
LT1765-1.8
l
1.764 1.8 1.836 V
LT1765-2.5
l
2.45 2.5 2.55 V
LT1765-3.3
l
3.234 3.3 3.366 V
LT1765-5
l
4.9 5 5.1 V
FB Input Current LT1765 (Adj)
l
0.25 0.5 μA
FB Input Resistance LT1765-1.8
LT1765-2.5
LT1765-3.3
LT1765-5
l
l
l
l
10.5
14.7
19
29
15
21
27.5
42
21
30
39
60
FB Error Amp Voltage Gain 0.4V < V
C
< 0.9V 150 350
FB Error Amp Transconductance
ΔI
VC
= ±10μA
l
500 850 1300 μMho
V
C
Pin Source Current V
FB
= V
NOM
– 17%
l
80 120 160 μA
V
C
Pin Sink Current V
FB
= V
NOM
+ 17%
l
70 110 180 μA
V
C
Pin to Switch Current Transconductance 5A/V
V
C
Pin Minimum Switching Threshold Duty Cycle = 0% 0.4 V
V
C
Pin 3A ISW Threshold 0.9 V
Maximum Switch Duty Cycle V
C
= 1.2V, I
SW
= 800mA, V
IN
= 6V
l
85
80
90 %
%
Minimum Boost Voltage Above Switch I
SW
= 3A
l
1.8 2.7 V
Boost Current I
SW
= 1A (Note 4)
I
SW
= 3A (Note 4)
l
l
20
70
30
140
mA
mA
SHDN Threshold Voltage
l
1.27 1.33 1.40 V
SHDN Threshold Current Hysteresis
l
4710 μA
SHDN Input Current (Shutting Down) SHDN = 60mV Above Threshold
l
–7 –10 –13 μA
SYNC Threshold Voltage 1.5 2.2 V
SYNC Input Frequency 1.6 2 MHz
SYNC Pin Resistance I
SYNC
= 1mA 20
The l denotes the specifi cations which apply over the full operating temperature range, otherwise specifi cations are at T
A
= 25°C.
V
IN
= 15V, V
C
= 0.8V, Boost = V
IN
+ 5V, SHDN, SYNC and switch open unless otherwise noted.
Note 3: Minimum input voltage is defi ned as the voltage where the internal
regulator enters lockout. Actual minimum input voltage to maintain a
regulated output will depend on output voltage and load current. See
Applications Information.
Note 4: Current fl ows into the BOOST pin only during the on period of the
switch cycle.