LTM4664 datasheet(20/138 Pages) AD

20 / 138 page

LTM4664A

Rev. 0

For more information www.analog.com

PIN FUNCTIONS

VINS1: (J15-J16) Power input pins to the first stage

divide by two. Place input capacitance between these

pins and GND.

4:1 Divider Section (Stage 2)

VINS2: (C1-C3) Power input pins to the second stage

divide by two. Place input capacitance between these pin

and GND.

SW3, SW4: (D1-D3), (G1-G3) Switching nodes for the

2nd stage CFLY Flying capacitor. See Block Diagram.

VINS2F: (D5) Input Voltage Sensing with Filtering. This

pin has a 1kΩ resistor in series from VINS2, and a 4700pf

capacitor to GND. The pin has a 1MΩ resistance to GND.

See Block Diagram.

INSNSS2–: (D6) Current sense comparator negative input,

connected to the negative node of the current sensing

resistor. Short to INSNSS2+ if not used.

INSNSS2+: (D7) Current sense comparator positive input,

connected to the positive node of the external current

sensing resistor. The current sensing resistor has to be

placed on the drain of the very top MOSFET. When the

voltage between INSNSS2+ pin and INSNSS2– pin is

higher than 50mV, the controller indicates an overcurrent

fault by pulling the FAULTS2 pin down. The INSNSS2+

pin is also used to source 95mA current to the VOUT2

pin during the pre-balance time in divider applications.

Connect directly to the drain of the very top MOSFET if

not used. See Application Schematic section.

HYS_PRGMS2: (E5) A resistor connected between this

pin and ground will set the window threshold of the win-

dow comparator that monitors the voltage difference

between (VINS2)/2 and VOUT2. There is a 10μA current

flowing out of this pin. See applications section.

OVP_SET: (E6) External + input for setting the VOUT2

trip level. The OVP_SET pin will have a voltage divider

to monitor the VOUT2 voltage and set to trip when the

divider midpoint on the OVP_SET pin exceeds the ref-

erence trip level on the VOUT2_SET pin. For example, if

the OVP_SET trip point was set for VTRIP, then RTOP =

((VTRIP/5.1V)-1) • 7.5K, with RTOP being the top resistor in

the divider, and RBOT is the bottom resistor in the divider.

RBOT set to 7.5k. If not used, tie this pin to INTVCCS2. See

4:1 Divider Application Information section.

OVP_TRIP: (E7) Open collector output that is used to trip

off input power and clamp hold up energy during an over

voltage fault on VOUT2. See Applications section.

TIMERS2: (F5) Charge Balance and Fault Timer Control

Input. A capacitor between this pin and ground sets the

amount of time to charge VOUT2 to (VINS2)/2. It also sets

the short-circuit retry time. See the 4:1 Divider Application

Information.

VOUT2_SET: (F6) External – comparator input for setting

the VOUT2 trip reference level. This can be done with a

resistor and 5.1V Zener from VIN. This secondary fault

protection is in and above the Fault protection for Stage

1 and Stage 2. The overall input voltage is divided down

by four, so VOUT2 will be 1/4 of VIN. The OVP_SET pin will

have a voltage divider to monitor the VOUT2 voltage and

set to trip when the divider midpoint on the OVP_SET pin

exceeds the reference trip level. If not used, tie this pin to

ground. See 4:1 Divider Application Information section.

EXTVCCS2: (F7) External Power Input to the Internal LDO

Connected to INTVCCS2. This LDO supplies INTVCCS2

power, bypassing the internal LDO powered from VIN2

whenever EXTVCCS2 is higher than 6.5V and VINS2 is

higher than 7V. Do not exceed 30V on this pin. This pin

can be driven with the VOUT2 output to limit power loss

in LDO with VINS2 at higher input voltage. See 4:1 Divider

Application Information section.

FREQS2: (G5) Frequency Set Pin. There is a precision

10μA current flowing out of this pin. A resistor to ground

sets a voltage which in turn programs the frequency.

See the 4:1 Divider Application Information section for

detailed information.

RUNS2: (G6) Stage 2 Run Control Input. Forcing RUNS2

below 1.2V shuts down the controller. When RUNS2 is

higher than 1.2V, internal circuitry starts up. There is a

1μA pull-up current flowing out of RUNS2 pin when the

RUNS2 pin voltage is below 1.2V and an additional 5μA

current flowing out of RUNS2 pin when the RUNS2 pin

voltage is above 1.2V. Use PGOODS1, and FAULTS1 from

stage one to enable stage 2.

LTM4664 Datasheet(PDF) 20 Page - Analog Devices

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