Datasheet

2
LTC1872
ABSOLUTE MAXIMUM RATINGS
W
WW
U
(Note 1)
Input Supply Voltage (V
IN
).........................–0.3V to 10V
SENSE
–
, NGATE Voltages ............ –0.3V to (V
IN
+ 0.3V)
V
FB
, I
TH
/RUN Voltages ..............................–0.3V to 2.4V
NGATE Peak Output Current (<10µs) ....................... 1A
Storage Ambient Temperature Range ... –65°C to 150°C
Operating Temperature Range (Note 2) .. –40°C to 85°C
Junction Temperature (Note 3).............................150°C
Lead Temperature (Soldering, 10 sec)..................300°C
PACKAGE/ORDER INFORMATION
W
U
U
T
JMAX
= 150°C, θ
JA
= 230°C/W
S6 PART MARKING
ORDER PART
NUMBER
LTC1872ES6
LTMK
Consult factory for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The ● denotes specifications that apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C. V
IN
= 4.2V unless otherwise specified. (Note 2)
PARAMETER CONDITIONS MIN TYP MAX UNITS
Input DC Supply Current Typicals at V
IN
= 4.2V (Note 4)
Normal Operation 2.4V ≤ V
IN
≤ 9.8V 270 420 µA
Sleep Mode 2.4V ≤ V
IN
≤ 9.8V 230 370 µA
Shutdown 2.4V ≤ V
IN
≤ 9.8V, V
ITH
/RUN = 0V 8 22 µA
UVLO V
IN
< UVLO Threshold 6 10 µA
Undervoltage Lockout Threshold V
IN
Falling ● 1.55 2.00 2.35 V
V
IN
Rising 1.85 2.10 2.40 V
Shutdown Threshold (at I
TH
/RUN) ● 0.15 0.35 0.55 V
Start-Up Current Source V
ITH
/RUN = 0V 0.25 0.5 0.85 µA
Regulated Feedback Voltage 0°C to 70°C(Note 5) ● 0.780 0.800 0.820 V
–40°C to 85°C(Note 5)
● 0.770 0.800 0.830 V
V
FB
Input Current (Note 5) 10 50 nA
Oscillator Frequency V
FB
= 0.8V 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 (Note 6) 114 120 mV
I
TH
/RUN 1
GND 2
V
FB
3
6 NGATE
5 V
IN
4 SENSE
–
TOP VIEW
S6 PACKAGE
6-LEAD PLASTIC SOT-23
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: The LTC1872E 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.
Note 3: T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
according to the following formula:
T
J
= T
A
+ (P
D
• θ
JA
°C/W)
Note 4: Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency.
Note 5: The LTC1872 is tested in a feedback loop that servos V
FB
to the
output of the error amplifier.
Note 6: Guaranteed by design at duty cycle = 30%. Peak current sense
voltage is V
REF
/6.67 at duty cycle <40%, and decreases as duty cycle
increases due to slope compensation as shown in Figure 2.