LTC3866 Datasheet, PDF (8/36 Pages) Linear Technology – Current Mode Synchronous Controller for Sub Milliohm DCR Sensing

LTC3866
Typical Performance Characteristics T_A = 25°C, unless otherwise noted.
Shutdown Current vs Temperature
50
45
40
35
30
25
20
15
10
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
3866 G22
Input Quiescent Current
vs Input Voltage without EXTV_CC
4.00
3.75
3.50
3.25
3.00
2.75
2.50
5 10 15 20 25 30 35 40
INPUT VOLTAGE (V)
3866 G23
Quiescent Current vs Temperature
without EXTV_CC
4.0
3.8
3.6
3.4
3.2
3.0
2.8
2.6
2.4
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
3866 G24
Pin Functions (FE/UF)
FREQ (Pin 1/Pin 22): Oscillator Frequency Control Input.
A 10µA current source flows out of this pin. Connecting
a resistor between this pin and ground sets a DC voltage
which in turn programs the oscillator frequency. Alterna-
tively, this pin can be driven with a DC voltage to vary the
frequency of the internal oscillator.
RUN (Pin 2/Pin 23): Run Control Input. A voltage above
1.22V turns on the IC. Pulling this pin below 1.14V causes
the IC to shut down. There is a 1μA pull-up current for the
pin. Once the RUN pin rises above 1.22V, an additional
4.5μA pull-up current is added to the pin.
TK/SS (Pin 3/Pin 24): Output Voltage Tracking and Soft-
Start Input. An internal soft-start current of 1.25μA charges
the external soft-start capacitor connected to this pin.
ITH (Pin 4/Pin 1): Current Control Threshold and Error
Amplifier Compensation Pin. The current comparator trip-
ping threshold is proportional with this voltage.
V_FB (Pin 5/Pin 2): Error Amplifier Feedback Input. This
pin receives the remotely sensed feedback voltage to set
the output voltage through an external resistive divider
connected to the DIFFOUT pin or the output.
DIFFOUT (Pin 6/Pin 3): Output of Remote Sensing Differ-
ential Amplifier. Connect this pin to V_FB through a resistive
divider to set the desired output voltage.
8
DIFFN (Pin 7/Pin 4): Negative Input of Remote Sensing
Differential Amplifier. Connect this pin close to the ground
of the output load.
DIFFP (Pin 8/Pin 5): Positive Input of Remote Sensing
Differential Amplifier. Connect this pin close to the output
load.
SNSD⁺ (Pin 9/Pin 6): First Positive Current Sense Input.
This pin is connected to sense the signal of the output
inductor’s DCR, it is to be used with a filter that matches
the bandwidth, L/DCR, of the inductor.
SNS^– (Pin 10/Pin 7): Negative Current Sense Input. This
negative input of the current comparator is to be connected
to the output.
SNSA⁺ (Pin 11/Pin 8): Second Positive Current Sense
Input. This input is to be connected to sense the signal of
the output’s inductor DCR with a filter bandwidth of five
times larger than L/DCR.
ILIM (Pin 12/Pin 9): Current Comparator Sense Voltage
Limit. Apply a DC voltage to set the maximum current
sense threshold for the current comparator.
CLKOUT (Pin 13/Pin 10): Clock Output Pin. The CLKOUT
signal is 180° out of phase to the rising edge of the IC
internal clock.
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