LTM8003 datasheet(12/28 Pages) AD

12 / 28 page

LTM8051

Rev. 0

For more information www.analog.com

PIN FUNCTIONS

VIN1 (Pin E7): Input power for the channel 1 regulator.

The VIN1 powers the internal control circuitry for channel

1/4 and is monitored by undervoltage lockout circuitry.

The VIN1 voltage must be greater than 3.0V for either

channel1/4 of the LTM8051 to operate. Decouple VIN1 to

ground with an external, low ESR capacitor. See Table 1

for recommended values.

VIN4 (Pin F7): Input power for the channel 4 regulator.

Decouple VIN4 to ground with an external, low ESR capaci-

tor. See Table 1 for recommended values.

VIN23 (Bank 5): Input power for the channel 2/3 regula-

tor. The VIN23 bank powers the internal control circuitry

for both channel 2/3 and is monitored by undervoltage

lockout circuitry. The VIN23 voltage must be greater than

3.0V for either channel2/3 of the LTM8051 to operate.

Decouple VIN23 to ground with an external, low ESR

capacitor. See Table 1 for recommended values.

VOUT1/2/3/4 (Bank 1/2/3/4): Power Output for channel

1/2/3/4, respectively. Apply the output filter capacitor and

the output load between these pins and GND pins.

GND (Bank 6): Tie these GND pins to a local ground plane

below the LTM8051 and the circuit components. In most

applications, the bulk of the heat flow out of the LTM8051

is through these pads, so the printed circuit design has a

large impact on the thermal performance of the part. See

the PCB Layout and Thermal Considerations sections for

more details. Return the feedback divider (RFB) to this net.

BIAS14/23 (Pin N3/A5): The internal regulator will draw

current from BIAS

n instead of VIN1 or VIN23 when BIASn

is tied to a voltage higher than 3.2V. For output voltages

of 3.3V and above this pin should be tied to VOUTn. If this

pin is tied to a supply other than VOUTn use a local bypass

capacitor on this pin.

CLKOUT14/23 (Pin D6/C6): Synchronization output.

When SYNC14/23>2.8V, the CLKOUT14/23 pin provides

a waveform about 90 degrees out-of-phase with Channel

1/2 respectively. This allows synchronization with other

regulators with up to four phases. When an external clock

is applied to the SYNC pin, the CLKOUT pin will output a

waveform with about the same phase, duty cycle, and fre-

quency as the SYNC waveform. In Burst Mode operation,

the CLKOUT pin will be internally grounded. Float this pin

if the CLKOUT function is not used. Do not drive this pin.

FB1/2/3/4 (Pin L2/D2/D1/L1): The LTM8051 regulates the

n pins to 800mV. Connect the feedback resistor to this

pin to set the output voltage.

PG1/2/3/4 (Pin L6/K6/K7/L7): The PG

n pin is the open-

drain output of an internal comparator. PG

n remains low

until the FB

n pin is within ±7.5% of the final regulation

voltage, and there are no fault conditions. PG

n is pulled

low during VINn UVLO, Thermal Shutdown, or when the

RUN

n pin is low.

RT14/23 (Pin K1/J1): Connect a resistor between RT

and ground to set the switching frequency. Do not drive

this pin.

RUN14/23 (Pin D7/C7): The corresponding channel of

the LTM8051 is shutdown when this pin is low and active

when this pin is high. Tie to VINn if shutdown feature is

not used. An external resistor divider from VINn can be

used to program a VINn threshold below which the cor-

responding channel of the LTM8051 will shut down. Do

not float this pin.

SHARE14/23 (Pin N5/A3): Sharing Control. Float

SHARE14 when VOUT1 and VOUT4 are load sharing.

Connect SHARE14 to VCC14 if VOUT1 and VOUT4 are inde-

pendent. Float SHARE23 when VOUT2 and VOUT3 are load

sharing. Connect SHARE23 to VCC23 if VOUT2 and VOUT3

are independent. Connect SHARE14 and SHARE23 if par-

allel all four channels. Connect this pin to the SHARE

pin of another LTM8051 when load sharing with another

LTM8051.

VCC14/23 (Pin N4/A4): Internal Regulator Bypass Pin. The

internal power drivers and control circuits are powered

from this voltage. VCCn current will be supplied from

BIAS

n if VBIASn > 3.2V, otherwise current will be drawn

from VINn. If VOUT1 and VOUT4 are load sharing, leave

VCC14 floating. If VOUT2 and VOUT3 are load sharing, leave

VCC23 floating. If VOUT1 and VOUT4 are independent volt-

ages, connect SHARE14 to VCC14; if VOUT2 and VOUT3

are independent voltages, connect SHARE23 to VCC23,

otherwise the LTM8051 will not regulate properly. Do not

load the VCCn with external circuitry.

LTM8003 Datasheet(PDF) 12 Page - Analog Devices

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