LTM8045 datasheet(16/54 Pages) AD

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LTM4655

Rev. 0

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INTVCC2 (G8): Channel 2 Internal Regulator, 3.3V Output

with Respect to VOUT2–. Channel 2 internal control circuits

and MOSFET drivers derive power from INTVCC2 bias.

Leave INTVCC2 open circuit. An LDO generates INTVCC2

from either SVIN2 or EXTVCC2, when RUN2 is logic high

(RUN2–GND > 1.2V). The INTVCC2 LDO is turned off when

RUN2 is logic low (RUN2–GND < 1.2V). (See EXTVCC2.)

EXTVCC1 (F3): External Bias, Auxiliary Input to the

INTVCC1 Regulator. When EXTVCC1–VOUT1– > 3.2V and

SVIN1 > 5V and RUN1–GND > 1.2V, the INTVCC1 LDO

derives power from EXTVCC1 bias instead of SVIN1. This

technique reduces LDO losses considerably, resulting in

a corresponding reduction in module junction tempera-

ture. For applications in which 4V < VOUT1+ – VOUT1– <

28V, connect EXTVCC1 to VOUT1+ through a 15Ω~110Ω

resistor and locally decouple EXTVCC1 to VOUT1– with a

1μF ceramic capacitor. Otherwise, connect EXTVCC1 to

VOUT1– or leave EXTVCC1 open circuit. See the Applications

Information section.

EXTVCC2 (F8): External Bias, Auxiliary Input to the

INTVCC2 Regulator. When EXTVCC2–VOUT2– > 3.2V and

SVIN2 > 5V and RUN2–GND >1.2V, the INTVCC2 LDO

derives power from EXTVCC2 bias instead of SVIN2. This

technique reduces LDO losses considerably, resulting in

a corresponding reduction in module junction tempera-

ture. For applications in which 4V < VOUT2+ – VOUT2– <

28V, connect EXTVCC2 to VOUT2+ through a 15Ω~110Ω

resistor and locally decouple EXTVCC2 to VOUT2– with a

1μF ceramic capacitor. Otherwise, connect EXTVCC2 to

VOUT2– or leave EXTVCC2 open circuit. See the Applications

Information section.

ISET1b (F1): 1.5nF Soft-Start Capacitor for Channel 1.

Connect ISET1b to ISET1a to achieve default soft-start

characteristics on channel 1, if desired. See ISET1a.

ISET2b (F6): 1.5nF Soft-Start Capacitor for Channel 2.

Connect ISET2b to ISET2a to achieve default soft-start

characteristics on channel 2, if desired. See ISET2a.

ISET1a (F2): Accurate 50μA Current Source. Positive

input to the error amplifier of channel 1. Connect a resis-

tor RISET1a = ((VOUT1+ – VOUT1–)/50μA) from this pin

to SVOUT1– local to the module to program the desired

channel 1 output voltage magnitude, VOUT1+ – VOUT1–. A

capacitor can be connected from ISET1a to SVOUT1– to

soft-start channel 1’s output voltage, i.e., reduce its start-

up inrush current. Connect ISET1a to ISET1b in order to

achieve default soft-start characteristics if desired. (See

ISET1b.)

In addition, the channel 1 output of the LTM4655 can

track a voltage applied to this pin. (See the Applications

Information section.)

ISET2a (F7): Accurate 50μA Current Source. Positive

input to the error amplifier of channel 1. Connect a resis-

tor RISET2a = ((VOUT2+ – VOUT2–)/50μA) from this pin

to SVOUT2– local to the module to program the desired

channel 2 output voltage magnitude, VOUT2+ – VOUT2–. A

capacitor can be connected from ISET2a to SVOUT2– to

soft-start channel 2’s output voltage, i.e., reduce its start-

up inrush current. Connect ISET2a to ISET2b in order

to achieve default soft-start characteristics if desired.

(See ISET2b.)

In addition, the channel 2 output of the LTM4655 can

track a voltage applied to this pin. (See the Applications

Information section.)

PGOOD1 (D1): Channel 1 Power Good Indicator, Open-

Drain Output Pin. PGOOD1 is high impedance when

PGDFB1–SVOUT1– is within approximately ±7.5% of

0.6V. PGOOD1 is pulled to GND when PGDFB1 is outside

this range.

PGOOD2 (D6): Channel 2 Power Good Indicator, Open-

Drain Output Pin. PGOOD2 is high impedance when

PGDFB2–SVOUT2– is within approximately ±7.5% of

0.6V. PGOOD2 is pulled to GND when PGDFB2 is outside

this range.

PIN FUNCTIONS

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