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V•I Chip Pre-Regulator Module

P048F048T24AL

Rev. 1.7

Page 8 of 14

PRELIMINARY

Pin / Control Functions

V•I Chip Pre-Regulator Module

+IN / -IN DC Voltage Ports

The V•I Chip maximum input voltage should not be exceeded. PRMs

have internal over / undervoltage lockout functions that prevent

operation outside of the specified input range. PRMs will turn on

when the input voltage rises above its undervoltage lockout. If the

input voltage exceeds the overvoltage lockout, PRMs will shut down

until the overvoltage fault clears. PC will toggle indicating an out of

bounds condition.

+OUT / -OUT Factorized Voltage Output Ports

These ports provide the Factorized Bus voltage output. The –OUT port

is connected internally to the –IN port through a current sense resistor.

The PRM has a maximum power and a maximum current rating and is

protected if either rating is exceeded. Do not short –OUT to –IN.

VC – VTM Control

downstream VTMs, enabling the VTMs and synchronizing the rise of

the VTM output voltage to that of the PRM. The VC port also provides

feedback to the PRM to compensate for voltage drop due to the VTM

output resistance. The PRM’s VC port should be connected to the VTM

VC port. A PRM VC port can drive a maximum of two (2) VTM VC ports.

PC – Primary Control

The PRM voltage output is enabled when the PC pin is open circuit

(floating). To disable the PRM output voltage, the PC pin is pulled low.

Open collector optocouplers, transistors, or relays can be used to

control the PC pin. When using multiple PRMs in a high power array,

the PC ports must be tied together to synchronize their turn on.

During an abnormal condition the PC pin will pulse (Fig.12) as the

PRM initiates a restart cycle. This will continue until the abnormal

condition is rectified. The PC should not be used as an auxiliary voltage

supply, nor should it be switched at a rate greater than 1 Hz.

TM – Factory Use Only

IL – Current Limit Adjust

The PRM has a preset, maximum, current limit set point. The IL port

may be used to reduce the current limit set point to a lower value. See

“adjusting current limits” on page 10.

PR – Parallel Port

The PR port signal, which is proportional to the PRM output power,

supports current sharing among PRMs. To enable current sharing, PR

ports should be interconnected. Bypass capacitance should be used

when interconnecting PR ports and steps should be taken to minimize

coupling noise into the interconnecting bus. Please consult Vicor

Applications Engineering regarding additional considerations.

VH – Auxiliary Voltage

VH is a gated, non-isolated, nominally 9 Volt, regulated DC voltage

(see “Auxiliary Pins” specifications, on Page 7) that is referenced to

SG. VH may be used to power external circuitry having a total current

consumption of no more than 5 mA.

SC – Secondary Control

The load voltage may be controlled by connecting a resistor or voltage

source to the SC port referenced to SG. The slew rate of the output

voltage may be controlled by controlling the rate-of-rise of the voltage

at the SC port (e.g., to limit inrush current into a capacitive load).

SG – Signal Ground

This port provides a low inductance Kelvin connection to –IN and

should be used as reference for the OS, CD, SC,VH and IL ports.

OS – Output Set

The application-specific value of the Factorized Bus voltage (Vf) is set

by connecting a resistor between OS and SG. Resistor value selection is

shown in Table 1 on Page 2, and described on Page 9. If no resistor is

connected, the PRM output will be approximately one volt. If set

resistor is not collocated with the PRM, a local bypass capacitor of

~200 pF may be required.

CD – Compensation Device

Adaptive Loop control is configured by connecting an external resistor

between the CD port and SG. Selection of an appropriate resistor

value (see Equation 2 on Page 9 and Table 1 on Page 2) configures the

PRM to compensate for voltage drops in the equivalent output

resistance of the VTM and the PRM-VTM distribution bus. If no resistor

is connected to CD, the PRM will be in Local Loop mode and will

regulate the +OUT / –OUT voltage to a fixed value.

Figure 15 — PRM pin configuration

Bottom View

4

3

2

1

+OUT

–OUT

+IN

–IN

VC

PC

TM

IL

VH

PR

NC

SG

SC

OS

NC

CD

A

B

C

D

E

F

G

H

J

K

L

M

N

P

AL Version

A

B

C

D

E

F

G

H

J

K

L

M

N

P

Signal Name

Designation

+IN

G1-K1,G2-K2

–IN

L1-P1, L2-P2

VC

A1,A2

PC

B1, B2

TM

C1, C2

IL

D1, D2

PR

F1, F2

VH

A3, A4

SC

B3, B4

SG

C3, C4

OS

D3, D4

CD

F3, F4

+OUT

G3-K3, G4-K4

–OUT

L3-P3, L4-P4