LTM4607 datasheet(8/28 Pages) LINER

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LTM8056

8056fa

For more information www.linear.com/LTM8056

PIN FUNCTIONS

RT(PinH1):TimingResistor.TheRTpinisusedtoprogram

the switching frequency of the LTM8056 by connecting a

resistor from this pin to ground. The range of oscillation is

100kHzto800kHz.TheApplicationsInformationsectionof

the data sheet includes a table to determine the resistance

value based on the desired switching frequency. Minimize

capacitance at this pin. A resistor to ground must be ap-

plied under all circumstances.

SYNC(PinH2):ExternalSynchronizationInput.TheSYNC

pin has an internal pull-down resistor. See the Synchroni-

zation section in Applications Information for details. Tie

this pin to GND when not used.

FB (Pin J1): Output Voltage Feedback. The LTM8056

regulates the FB pin to 1.2V. Connect the FB pin to a

resistive divider between the output and GND to set the

output voltage. See Table 1 for recommended FB divider

resistor values.

COMP (Pin J2): Compensation Pin. The LTM8056 is

equipped with internal compensation that works well with

most applications. In some cases, the performance of the

LTM8056 can be enhanced by modifying the control loop

compensation by applying a capacitor or RC network to

this pin.

SS (Pin K1): Soft-Start. Connect a capacitor from this pin

to GND to increase the soft-start time. Soft-start reduces

the input power source’s surge current by gradually in-

creasing the controller’s current limit. Larger values of the

soft-start capacitor result in longer soft-start times. If no

soft-start is required, leave this pin open.

CTL (Pin K2): Current Sense Adjustment. Apply a voltage

below 1.2V to reduce the current limit threshold of IOUT.

Drive CTL to less than about 50mV to stop switching. The

CTL pin has an internal pull-up resistor to 2V. If not used,

leave this pin open.

IOUTMON (Pin L2): Output Current Monitor. This pin pro-

duces a voltage that is proportional to the voltage between

VOUT and IOUT. IOUTMON will equal 1.2V when VOUT – IOUT

= 58mV. This feature is generally useful only if a current

sense resistor is applied between VOUT and IOUT. This is

a high impedance output. Use a buffer to drive a load.

IINMON (Pin L3): Input Current Monitor. This pin produces

a voltage that is proportional to the voltage between IIN

and VIN. IINMON will equal 1V when IIN-VIN = 50mV. This

feature is generally useful only if a current sense resistor

is applied between VIN and IIN.

RUN(PinL4):LTM8056Enable.RaisetheRUNpinvoltage

above 1.2V for normal operation. Above 1.2V (typical), but

below 6V, the RUN pin input bias current is less than 1μA.

Below 1.2V and above 0.3V, the RUN pin sinks 3μA so

the user can define the hysteresis with the external resis-

tor selection. This will also reset the soft-start function.

If RUN is 0.3V or less, the LTM8056 is disabled and the

SVIN quiescent current is below 1μA.

IIN (Pin L9): Input Current Sense. Tie this pin to the input

current sense resistor. The input average current sense

threshold is 50mV, so the LTM8056 will regulate the input

current to 50mV/RSENSE, where RSENSE is the value of the

input current sense resistor in ohms. Tie to VIN when not

used.Keepthispinwithin±0.5VofVINunderallconditions.

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