Datasheet
LT3845A
3
3845afa
PARAMETER CONDITIONS MIN TYP MAX UNITS
V
IN
Operating Voltage Range (Note 4)
V
IN
Minimum Start Voltage
V
IN
UVLO Threshold (Falling)
V
IN
UVLO Threshold Hysteresis
l
l
l
4
3.6
3.8
670
60
7.5
4
V
V
V
mV
V
IN
Supply Current
V
IN
Burst Mode Current
V
IN
Shutdown Current
V
CC
> 9V
V
BURST_EN
= 0V, V
FB
= 1.35V
V
SHDN
= 0V
l
20
20
9
15
µA
µA
µA
BOOST Operating Voltage Range
BOOST Operating Voltage Range (Note 5)
BOOST UVLO Threshold (Rising)
BOOST UVLO Threshold Hysteresis
V
BOOST
– V
SW
V
BOOST
– V
SW
V
BOOST
– V
SW
l
l
5
400
75
20
V
V
V
mV
BOOST Supply Current (Note 6)
BOOST Burst Mode Current
BOOST Shutdown Current
V
BURST_EN
= 0V
V
SHDN
= 0V
1.4
0.1
0.1
mA
µA
µA
V
CC
Operating Voltage Range (Note 5)
V
CC
Output Voltage
V
CC
UVLO Threshold (Rising)
V
CC
UVLO Threshold Hysteresis
Over Full Line and Load Range
l
l
8
6.25
500
20
8.3
V
V
V
mV
V
CC
Supply Current (Note 6)
V
CC
Burst Mode Current
V
CC
Shutdown Current
V
CC
Current Limit
V
BURST_EN
= 0V
V
SHDN
= 0V
l
l
–40
3
100
20
–150
3.7 mA
µA
µA
mA
Error Amp Reference Voltage Measured at V
FB
Pin
l
1.224
1.215
1.231 1.238
1.245
V
V
V
FB
Pin Input Current V
FB
= 1.231V 25 nA
SHDN Enable Threshold (Rising)
SHDN Threshold Hysteresis
l
1.3 1.35
120
1.4 V
mV
Sense Pins Common Mode Range
Current Limit Sense Voltage
Reverse Protect Sense Voltage
Reverse Current Inhibit Offset
V
SENSE
+
– V
SENSE
–
V
SENSE
+
– V
SENSE
–
, V
BURST_EN
= V
CC
V
BURST_EN
= 0V or V
BURST_EN
= V
FB
l
l
0
90
100
–100
10
36
115
V
mV
mV
mV
Input Current (I
SENSE
+
+ I
SENSE
–
) V
SENSE(CM)
= 0V
V
SENSE(CM)
= 2V
V
SENSE(CM)
> 4V
800
–20
–300
µA
µA
µA
Operating Frequency
l
270 300 330 kHz
Minimum Programmable Frequency
Maximum Programmable Frequency
l
l
500
100 kHz
kHz
External Sync Frequency Range
l
100 600 kHz
SYNC Input Resistance 40 kΩ
SYNC Voltage Threshold
l
1.4 2 V
Soft-Start Capacitor Control Current 2 µA
Error Amp Transconductance
l
270 340 410 µS
Error Amp DC Voltage Gain 62 dB
Error Amp Sink/Source Current ±30 µA
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 20V, V
CC
= BOOST = BURST_EN = 10V, SHDN = 2V, R
SET
= 49.9kΩ,
SENSE
–
= SENSE
+
= 10V, SGND = PGND = SW = SYNC = 0V, unless otherwise noted.