LT4180
5
4180fb
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pin FuncTions
INTV
CC
(Pin 1): The LDO Output. A low ESR ceramic
capacitor provides decoupling and output compensation.
1µF or more should be used.
DRAIN (Pin 2): Open-Drain of the Output Transistor. This
pin drives either the LED in an opto-isolator, or pulls down
on the regulator control pin.
COMP (Pin 3): Gate of the Output Transistor. This pin allows
additional compensation. It must be left open if unused.
CHOLD1 (Pin 4): Connects to track/hold amplifier hold
capacitor. The other end of this capacitor should be Kelvin
connected to GND.
GUARD2 (Pin 5): Guard Ring Drive for CHOLD2.
CHOLD2 (Pin 6): Connects to track/hold amplifier hold
capacitor. The other end of this capacitor should be Kelvin
connected to GND.
GUARD3 (Pin 7): Guard Ring Drive for CHOLD3.
CHOLD3 (Pin 8): Connects to track/hold amplifier hold
capacitor. The other end of this capacitor should be Kelvin
connected to GND.
GUARD4 (Pin 9): Guard Ring Drive for CHOLD4.
CHOLD4 (Pin 10): Connects to track/hold amplifier hold
capacitor. The other end of this capacitor should be Kelvin
connected to GND.
FB (Pin 11): Receives the feedback voltage from an exter-
nal resistor divider across the main output. An (optional)
capacitor
to ground may be added to eliminate high
frequency
noise. The time constant for this RC network
should be no greater than 0.1 times the dither frequency.
For example, with f
DITHER
= 1kHz,
t
= 0.1ms.
GND (Pin 12): Ground.
COSC (Pin 13): Oscillator Timing Capacitor. Oscillator
frequency is set by this capacitor and ROSC. For best ac-
curacy, the minimum recommended capacitance is 100pF.
ROSC (Pin 14): Oscillator Timing Resistor. Oscillator
frequency is set by this resistor and COSC.
OSC (Pin 15): Oscillator Output. This output may be
used to synchronize the switching regulator to the
Virtual Remote Sense. This is a high current output capable
of driving opto-isolators. Other isolation methods may
also be used with this output.
DIV2 (Pin 16): Dither Division Ratio Programming Pin.
DIV1 (Pin 17): Dither Division Ratio Programming Pin.
DIV0 (Pin 18): Dither Division Ratio Programming Pin.
Use the following table to program the dither division
ratio (f
OSC
/f
DITHER
)
Table 1. Programming the Dither Division Ratio (f
OSC
/f
DITHER
)
DIV2 DIV1 DIV0 DIVISION RATIO
0 0 0 8
0 0 1 16
0 1 0 32
0 1 1 64
1 0 0 128
1 0 1 256
1 1 0 512
1 1 1 1024
For example, f
DITHER
= f
OSC
/128 with DIV2 = 1 and DIV1
= DIV0 = 0.
SPREAD (Pin 19): Spread Spectrum Enable Input. Dither
phasing is pseudo-randomly adjusted when SPREAD is
tied high.
OV (Pin 20): Overvoltage Comparator Input. This prevents
line drop correction when wiring drops would cause ex-
cessive switching power supply output voltage. Set OV
so V
REG(MAX)
≤ 1.50V
LOAD
.
RUN (Pin 21): The RUN pin provides the user with an ac-
curate means for sensing the input voltage and program-
ming the start-up threshold for the line drop corrector.
SENSE (Pin 22): Current Sense Input. This input connects
to the current sense resistor. Kelvin connect to R
SENSE
.
V
PP
(Pin 23): Connect this pin to INTV
CC
.
V
IN
(Pin 24): Main Supply Pin. V
IN
must be locally bypassed
to ground. Kelvin connect the current sense resistor to
this pin and minimize interconnect resistance.
