Gm x Ro

A =

IT1 = ITRO x

§

¨

©

1+

R1

R2

+ VRS1 -

RS1

CTRO

+5V

R2

R1

IT1

Current

Share

Transconductance

Amplifie

r

GND

CSP

CS

TRO

RSO

R

R

R

R

CSM

CSO

Remote Sense

Driver

LM5080

SHR

8R

8R

ITRO

RTRO

NRND

LM5080

SNVS387C – SEPTEMBER 2005 – REVISED MARCH 2013

www.ti.com

Figure 14. LM5080 Showing the RSO Buffer Configured to Boost Transconductance

The effective output current from the TRO pin can be multiplied to increase the current share loop gain if

necessary. R1 should be at least 10k

Ω.

REMOTE SENSE ADJUST MODES

The two remote sense adjust modes (positive and negative) achieve current sharing by controlling either remote

sense input of the power converter. These configurations for the LM5080 are shown in Figure 15 and Figure 16.

To understand the sharing mechanism, assume for a moment the SHR pin is disconnected from the share bus.

Connecting RSO and CSO configures the current sharing amplifier as a differential amplifier with a gain of one.

The CSP and RSO voltage will be identical and independent of the voltage across the sense resistor. Hence the

voltage regulation loop of each power converter is unaffected by the LM5080 when the SHR bus is open.

When the SHR pins are connected, the small signal transfer functions between the sense resistor voltages (VRS)

and the power supplies negative remote sense voltages (VSNS) are:

VSNS1 = A/4 x (VRS1 – VRS2)

VSNS2 = A/4 x (VRS2 – VRS1)

where

•

•

gm = current share amplifier transconductance (8.7mA/V)

•

Ro = output impedance of TRO pin (typically 6 M

Ω)

10

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