TYPICAL PERFORMANCE CHARACTERISTICS
LTC1872B
Reference Voltage
vs Temperature
825
VIN = 4.2V
820
815
810
805
800
795
790
785
780
775
–55 –35 –15 5 25 45 65 85 105 125
TEMPERATURE (°C)
1872B G01
Normalized Oscillator Frequency
vs Temperature
10
VIN = 4.2V
8
6
4
2
0
–2
–4
–6
–8
–10
–55 –35 –15 5 25 45 65 85 105 125
TEMPERATURE (°C)
1872B G02
Undervoltage Lockout Trip
Voltage vs Temperature
2.24
VIN FALLING
2.20
2.16
2.12
2.08
2.04
2.00
1.96
1.92
1.88
1.84
–55 –35 –15 5 25 45 65 85 105 125
TEMPERATURE (°C)
1872B G03
Maximum Current Sense Trip
Voltage vs Duty Cycle
130
VIN = 4.2V
120
TA = 25°C
110
100
90
80
70
60
50
20 30 40 50 60 70 80 90 100
DUTY CYCLE (%)
187B2 G04
Shutdown Threshold
vs Temperature
600
VIN = 4.2V
560
520
480
440
400
360
320
280
240
200
–55 –35 –15 5 25 45 65 85 105 125
TEMPERATURE (°C)
1872B G05
PIN FUNCTIONS
ITH/RUN (Pin 1): This pin performs two functions. It
serves as the error amplifier compensation point as well as
the run control input. Nominal voltage range for this pin is
0.7V to 1.9V. Forcing this pin below 0.35V causes the
device to be shut down. In shutdown all functions are
disabled and the NGATE pin is held low.
GND (Pin 2): Ground Pin.
VFB (Pin 3): Receives the feedback voltage from an exter-
nal resistive divider across the output.
SENSE– (Pin 4): The Negative Input to the Current Com-
parator.
VIN (Pin 5): Supply Pin. Must be closely decoupled to GND
Pin 2.
NGATE (Pin 6): Gate Drive for the External N-Channel
MOSFET. This pin swings from 0V to VIN.
3