LTC1771
ELECTRICAL CHARACTERISTICS
The
q
denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C.
V
IN
= 10V, V
RUN
= open unless otherwise specified.
SYMBOL
V
RUN/SS
I
RUN
PGATE t
r
, t
f
PARAMETER
RUN/SS Pin Threshold
Source Current
PGATE Transition Time (Note 7)
Rise Time
Fall Time
CONDITIONS
V
RUN/SS
Rising
V
RUN
= 0V, V
IN
= 2.8V to 18V
C
LOAD
= 2000pF
C
LOAD
= 2000pF
q
MIN
0.5
0.3
TYP
1.0
1
80
90
MAX
2
3
UNITS
V
µA
ns
ns
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
according to the following formulas:
LTC1771S8: T
J
= T
A
+ (P
D
)(110°C/W)
LTC1771MS8: T
J
= T
A
+ (P
D
)(150°C/W)
Note 3:
The LTC1771E is guaranteed to meet performance specifications
from 0°C to 70°C. Specifications over the – 40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls. The LTC1771I is guaranteed and tested
over the – 40°C to 85°C operating temperature range.
Note 4:
Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency. See Applications Information.
Note 5:
The LTC1771 is tested in a feedback loop that servos V
FB
to the
balance point for the error amplifier (V
ITH
= 1.23V).
Note 6:
No-load supply current consists of sleep mode current (9µA
typical) plus a small switching component necessary to overcome
Schottky diode leakage and feedback resistor current.
Note 7:
t
r
and t
f
measured at 10% to 90% levels.
PI FU CTIO S
RUN/SS (Pin 1):
The voltage level on this pin controls
shutdown/run mode (ground = shutdown, open/high =
run). Connecting an external capacitor to this pin provides
soft-start.
I
TH
(Pin 2):
Error Amplifier Compensation Point. The
current comparator threshold increases with this control
voltage. Nominal voltage range for this pin is 0V to 3V.
V
FB
(Pin 3):
Feedback of Output Voltage for Comparison
to Internal 1.23V Reference. An external resistive divider
across the output is returned to this pin.
GND (Pin 4):
Ground Pin.
PGATE (Pin 5):
High Current Gate Driver for External
P-Channel MOSFET Switch. Voltage swing is from ground
to V
IN
.
V
IN
(Pin 6):
Main Input Voltage Supply Pin.
SENSE (Pin 7):
Current Sense Input for Monitoring Switch
Current. Maximum switch current and Burst Mode
threshold is programmed with an external resistor be-
tween SENSE and V
IN
.
MODE (Pin 8):
Burst Mode Enable/Disable Pin. Connect-
ing this pin to V
IN
(or above 2V) enables Burst Mode
operation, while connecting this pin to ground disables
Burst Mode operation. Do not leave floating.
U
U
U
3
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