LTM4650 datasheet(9/28 Pages) AD

9 / 28 page

LTM4660

Rev. 0

For more information www.analog.com

PIN FUNCTIONS

EXTVCC (K10): External Power Input to an Internal LDO

Connected to INTVCC. This LDO supplies INTVCC power,

bypassing the internal LDO powered from VIN whenever

EXTVCC is higher than 8V. Do not float or exceed 20V on

this pin. Connect EXTVCC to GND, if the features is unused.

To reduce internal module temperature rise, it is strongly

recommended to bias EXTVCC with 8VDC or higher. For

applications where VOUT ≥ 8V, there is an easy way: con-

nect VOUT to EXTVCC. For applications where VOUT < 8V, it

is strongly recommended to drive EXTVCC to 8V (or higher)

with an external bias supply. When driving EXTVCC exter-

nally, take precautions to ensure EXTVCC ≤ VIN at all times.

TEMP (K11): Temperature Sensing Input. Using a PTC

resistor as the lower leg of a resistor divider, connect the

TEMP pin to the common point of the divider. The PTC

resistor is used to monitor a hot spot on the PCB. Once

it reaches the TEMP threshold of 1.22V, the LTM4660

stops switching for 100ms before retrying. Ground this

pin if not used.

VFB (K12): Error Amplifier Feedback Input. Connect resis-

tor RVFB from this pin to SGND in order to configure the

VOUT output voltage setting. RVFB is given by Equation 1.

RVFB (kΩ) =

60.4

VOUT

VVFB

− 1

⎛

⎝⎜

⎞

⎠⎟

(1)

When EXT_REF is connected to INTVCC, the module regu-

lates the VFB pin at 0.8V, nominal. If EXT_REF is used or

TRACK/SS is externally driven to influence the VFB tar-

get servo voltage, the value of RVFB must be computed

accordingly. (See the Applications Information section.)

RUN (L3): Run Control Input. A voltage above 1.3V turns

the LTM4660 ON. A voltage below 1.1V causes the mod-

ule to shutdown. There is a 1μA pull-up current on this

pin when its voltage is below 1.3V.

SGND (L4, L12, M12): Signal Ground. All small-signal

components and compensation components (if used)

should connect to this signal SGND, which connects to

GND internal to the module. It is not necessary to connect

SGND to GND externally.

TRACK/SS (L9): Output Voltage Tracking and Soft-Start

Input. The LTM4660 regulates the VFB voltage to the low-

est of three voltages: 0.8V, the voltage on the EXT_REF

pin or the voltage on the TRACK/SS pin. An internal 10μA

pull-up current source is connected to this pin. A capaci-

tor to SGND at this pin sets the ramp time to the final

regulated output voltage. Alternatively, a resistor divider

from another voltage supply connected to this pin allows

the LTM4660 output voltage to track the other supply

during start-up.

HYS_PRGM (L11): There is a 10μA current flowing out

of this pin. A voltage created by connecting a resistor

from this pin to SGND sets an equal amount of window

threshold around VIN/2 to a window comparator. When

the voltage at MIDSNS is not within this window threshold,

FAULT will be pulled low and switching will stop. CFLY and

CMID will be rebalanced to half of VIN before resuming

normal operation.

PGOOD (M2): Power Good Pin. This is an open drain

output. PGOOD is pulled to ground when voltage at VFB

pin falls below 7.5% or rises above 8.5% of its set point.

It will also be pulled low when FAULT is tripped.

MODE/PLLIN (M3): Mode Selection or External

Synchronization Input to Phase Detector. When external

synchronization is not used, this pin selects the operating

modes and can be tied to SGND, to INTVCC or left open

circuit. If the pin is connected to SGND, it enables forced

continuous mode while a connection to INTVCC enables

pulse-skipping mode. Floating the pin enables Burst Mode

operation. For external sync, apply a clock signal to this

pin. The integrated PLL along with its internal compen-

sation network will synchronize the internal oscillator to

external clock. Forced continuous mode will be enabled

when an external clock is applied.

CLKOUT (M4): Clock Output Pin. This pin outputs a

clock 180° out of phase with the main operating clock

of the LTM4660.

EXT_REF (M9): External Reference Input. A voltage

applied to this pin forces the VFB to regulate to this volt-

age. Internal clamps set at 0.45V and 0.9V limit the lower

and upper bounds of VFB regulation that EXT_REF can

LTM4650 Datasheet(PDF) 9 Page - Analog Devices

LTM4650 Datasheet(HTML) 9 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

Datasheet Descarga

Enlace URL