Datasheet

LTC3872
3
3872fc
For more information www.linear.com/LTC3872
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 LTC3872 is tested under pulsed load conditions such that
T
J
≈T
A
. The LTC3872E is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 85°C operating
junction temperature range are assured by design, characterization and
correlation with statistical process controls. The LTC3872I is guaranteed
over the –40°C to 125°C operating junction temperature range. The
LTC3872H is guaranteed over the full –40°C to 150°C operating junction
temperature range. The maximum ambient temperature consistent with
these specifications is determined by specific operating conditions in
conjunction with board layout, the rated package thermal impedance and
other environmental factors.
PARAMETER CONDITIONS MIN TYP MAX UNITS
Input Voltage Range
l
2.75 9.8 V
Input DC Supply Current
Normal Operation
Shutdown
UVLO
Typicals at V
IN
= 4.2V (Note 4)
2.75V ≤ V
IN
≤ 9.8V
V
RUN/SS
= 0V
V
IN
< UVLO Threshold
250
8
20
400
20
35
µA
µA
µA
Undervoltage Lockout Threshold V
IN
Rising
V
IN
Falling
l
l
2.3
2.05
2.45
2.3
2.75
2.55
V
V
Shutdown Threshold (at RUN/SS) V
RUN/SS
Falling
V
RUN/SS
Rising
l
l
0.6
0.65
0.85
0.95
1.05
1.15
V
V
Regulated Feedback Voltage (Note 5) LTC3872E
LTC3872I and L
TC3872H
l
l
1.182
1.178
1.2
1.2
1.218
1.218
V
V
Feedback Voltage Line Regulation 2.75V < V
IN
< 9V (Note 5) 0.14 mV/V
Feedback Voltage Load Regulation V
ITH
= 1.6V (Note 5)
V
ITH
= 1V (Note 5)
0.05
–0.05
%
%
V
FB
Input Current (Note 5) 25 50 nA
RUN/SS Pull Up Current V
RUN/SS
= 0 0.35 0.7 1.25 µA
Oscillator Frequency
Normal Operation V
FB
= 1V 500 550 650 kHz
Gate Drive Rise Time C
LOAD
= 3000pF 40 ns
Gate Drive Fall Time C
LOAD
= 3000pF 40 ns
Peak Current Sense Voltage IPRG = GND (Note 6) LTC3872E
LTC3872I
LTC3872H
l
l
l
80
70
65
100
100
100
120
120
120
mV
mV
mV
IPRG = Float
LTC3872E
LTC3872I
LTC3872H
l
l
l
145
135
130
170
170
170
195
195
195
mV
mV
mV
IPRG = V
IN
LTC3872E
LTC3872I
LTC3872H
l
l
l
240
225
215
270
270
270
290
290
290
mV
mV
mV
Default Internal Soft-Start Time 1 ms
The l denotes the specifications which apply over the specified operating
temperature range, otherwise specifications are at T
A
= 25°C (Note 2). V
IN
= 4.2V unless otherwise noted.
Note 3: T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
according to the following formula:
LTC3872TS8: T
J
= T
A
+ (P
D
• 195°C/W)
LTC3872DDB: T
J
= T
A
+ (P
D
• 76°C/W)
Note 4: The dynamic input supply current is higher due to power MOSFET
gate charging (Q
G
• f
OSC
). See Applications Information.
Note 5: The LTC3872 is tested in a feedback loop which servos V
FB
to
the reference voltage with the I
TH
pin forced to the midpoint of its voltage
range (0.7V ≤ V
ITH
≤ 1.9V, midpoint = 1.3V).
Note 6: Rise and fall times are measured at 10% and 90% levels.
elecTrical characTerisTics