Datasheet

LTC1871-7
6
18717fd
Typical perForMance characTerisTics
Frequency vs Temperature
Maximum Sense Threshold
vs Temperature
SENSE Pin Current vs Temperature
INTV
CC
Load Regulation INTV
CC
Line Regulation
INTV
CC
Dropout Voltage
vs Current, Temperature
RUN (Pin 1): The RUN pin provides the user with an
accurate means for sensing the input voltage and pro-
gramming the start-up threshold for the converter. The
falling RUN pin threshold is nominally 1.248V and the
comparator has 100mV of hysteresis for noise immunity.
When the RUN pin is below this input threshold, the IC
is shut down and the V
IN
supply current is kept to a low
value (typ 10µA). The Absolute Maximum Rating for the
voltage on this pin is 7V.
I
TH
(Pin 2): Error Amplifier Compensation Pin. The current
comparator input threshold increases with this control
voltage. Nominal voltage range for this pin is 0V to 1.40V.
FB (Pin 3): Receives the feedback voltage from the external
resistor divider across the output. Nominal voltage for this
pin in regulation is 1.230V.
FREQ (Pin 4): A resistor from the FREQ pin to ground
programs the operating frequency of the chip. The nominal
voltage at the FREQ pin is 0.6V.
pin FuncTions
TEMPERATURE (°C)
–50
275
GATE FREQUENCY (kHz)
280
290
295
300
325
310
0
50
75
18717 G13
285
315
320
305
–25 25
100
125
150
TEMPERATURE (°C)
–50
140
MAX SENSE THRESHOLD (mV)
145
150
155
160
–25 0 25 50
18717 G14
75 100 125 150
TEMPERATURE (°C)
–50
25
SENSE PIN CURRENT (µA)
30
35
0
50
75
18717 G15
–25 25
100
125
150
GATE HIGH
V
SENSE
= 0V
0
INTV
CC
VOLTAGE (V)
7.0
30 50 80
18717 G16
6.9
6.8
10 20
40
60 70
V
IN
= 8V
V
IN
(V)
0
6.9
INTV
CC
VOLTAGE (V)
7.0
7.1
10 20
30
40
18717 G17
7.2
5 15
25
35
INTV
CC
LOAD (mA)
0
0
DROPOUT VOLTAGE (mV)
50
150
200
250
500
350
5
10
18717 G18
100
400
450
300
15
20
150°C
75°C
125°C
25°C
–50°C
0°C