D710 データシートの表示（PDF） - Semtech Corporation

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D710

500 MHz Pin Electronics Driver,Window Comparator, and Load

Semtech Corporation 

Edge710

EDGE HIGH-PERFORMANCE PRODUCTS

Circuit Description (continued)

Source and Sink Current Levels

Commutating Voltage Compensation

The amount of current that the diode bridge can source

and sink is adjustable from 0 mA to 35 mA. The source

and sink levels are separate and independent.

ISC_IN and ISK_IN are current controlled inputs whose

voltage level is held very close to ground (<100 mV

variation) over the entire legal current input range.

The VCM_CAP pin is an op amp compensation node that

requires a fixed .01 µF chip capacitor (with good high

frequency characteristics) to ground. This capacitor is

used to compensate an internal node on the on-chip buffer

for the commutating voltage input.

Split Load

There is a nominal gain of 20 between the ISC_IN current

and the bridge source current.

ISOURCE = 20 * ISC_IN

There is a nominal gain of –20 between the ISK_IN current

and the bridge sink current.

ISINK = –20 * ISK_IN

The VCM_OUT_A is the actual commutating voltage

generated by the on-chip buffer. VCM_OUT_A is also

connected to the upper half of the diode bridge, and is

responsible for sinking the programmed source current

when the load is sinking current from the DUT.

VCM_OUT_B is connected to the lower half of the diode

bridge, and is responsible for providing the sink current

when the load is sourcing current to the DUT.

Because the inversion creates a 180˚ phase shift between

ISK_IN and ISINK, there is a tendency toward instability.

A minimum of 500 W of external series resistance should

be used between an external voltage or current source

and the ISC_IN and ISK_IN pins to ensure stability. Stray

capacitance at the ISK_IN pin should be kept to a

minimum. PCB layout should minimize coupling between

ISK_IN and LOAD.

Caution: The ISKIN and ISCIN inputs are designed for

positive current between 0 mA and 1.75 mA flowing into

the part. Care should be taken to insure that current is

never required to flow out of the part on these two nodes.

VCM_OUT_B does NOT have an on-chip buffer. To

configure the load as a standard active diode bridge,

connect VCM_OUT_A and VCM_OUT_B together off-chip.

Or, to configure the load as a split load, an external buffer

must be used for VCM_OUT_B.

External Bridge Connections

Access to the top and bottom of the diode bridge is granted

through a 1 KW resistor. Pins BRIDGE_SC and BRIDGE_SK

allow external current sources to be used instead of the

internal I_SOURCE and I_SINK sources. These external

pins are useful when extremely accurate source and sink

currents are required for low current operation.

VCM_IN

 2000 Semtech Corp.

I_SOURCE

VCM_OUT_A

I_SINK

VCM_OUT_B

6

1KΩ

BRIDGE_SC

LOAD

1KΩ

BRIDGE_SK

www.semtech.com

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