Datasheet

3
LTC1879
1879f
The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are T
A
= 25°C.
V
IN
= 5V unless otherwise noted.
ELECTRICAL CHARACTERISTICS
V
RUN
RUN Threshold V
RUN
Ramping Up ● 0.2 0.7 1.5 V
I
RUN
RUN Input Current V
RUN
= 0V ±0.01 ±1 µA
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: The LTC1879E is guaranteed to meet specified performance from
0°C to 70°C. Specifications over the –40°C to 85°C operating ambient
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:
LTC1879: T
J
= T
A
+ (P
D
× 140°C/W)
Note 4: The LTC1879 is tested in a feedback loop which servos V
FB
to the
balance point for the error amplifier (V
ITH
= 1.2V)
Note 5: Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency.
Note 6: This IC includes overtemperature protection that is intended to
protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
temperature may impair device reliability.
R
DS(ON)
vs Temperature
Oscillator Frequency
vs Temperature
Oscillator Frequency
vs Supply Voltage
TYPICAL PERFOR A CE CHARACTERISTICS
UW
DC Supply Current
vs Temperature
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
R
DS(ON)
vs Input Voltage
TEMPERATURE (°C)
–50 –25 0 25 50 75 100 125
R
DS(ON)
(Ω)
1879 G01
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
V
IN
= 5V
V
IN
= 5V
V
IN
= 10V
V
IN
= 10V
SYNCHRONOUS SWITCH
MAIN SWITCH
TEMPERATURE (°C)
–50 –25 0 25 50 75 100 125
FREQUENCY (kHz)
1879 G02
595
575
555
535
515
495
V
IN
= 5V
SUPPLY VOLTAGE (V)
2 4 6810
OSCILLATOR FREQUENCY (kHz)
1879 G03
600
590
580
570
560
550
540
530
520
510
500
TEMPERATURE (°C)
–50
0 50 100 125
SUPPLY CURRENT (µA)
1879 G04
300
250
200
150
100
50
0
PULSE SKIPPING MODE
Burst Mode OPERATON
V
IN
= 5V
DC Supply Current
vs Input Voltage
INPUT VOLTAGE (V)
0
0
DC SUPPLY CURRENT (µA)
50
100
150
200
250
300
2468
1879 G05
10
PULSE SKIPPING MODE
Burst Mode OPERATION
INPUT VOLTAGE (V)
2
0
R
DS(ON)
(Ω)
0.1
0.2
0.3
0.4
46
8
10
1879 G06
0.5
0.6
35
7
9
SYNCHRONOUS
SWITCH
MAIN
SWITCH