Pre-Regulator Module

PR036A480T012FP

vicorpower.com

Rev. 1.1

Page 8 of 13

PIN / CONTROL FUNCTIONS

Figure 14 — VI BRICK PRM pin configuration (viewed from pin side).

+In / -In DC Voltage Ports

The VI BRICK 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

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.11) 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 “adjust-

ing current limits” on page 11.

PR – Parallel Port

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

supports current sharing of two 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. Terminate this port with a 10 k

equivalent resistance to SG, e.g. 10 k for a single PRM, 20 k each for 2

PRMs in parallel, 30 k each for 3 PRMs in parallel etc.. Please consult Vicor

Applications Engineering regarding additional considerations when

paralleling more than two PRMs.

VH – Auxiliary Voltage

VH is a gated (e.g. mirrors PC), 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 under either transient or

steady state conditons including turn-on.

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 9, and described on Page 10. If no resistor is connected,

the PRM output will be approximately one volt. If set resistor is not collo-

cated 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 10 and Table 1 on Page 9) 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.