Philips Semiconductors

Product data

NE57810

Advanced DDR memory termination power

with external reference in

2003 Sep 12

10

The NE57810 allows use of an external reference voltage to set its

voltage and current to be drawn from a power supply bus that is not

the DDR RAM supply voltage. This may have some advantages

when you are attempting to better match the power being drawn

from the outputs emerging from main system power supply. This can

be seen in Figure 13.

The internal reference voltage is set by two matched 100 k

Ω

pins of the NE57810.

an external resistor divider whose resistor values are less than 5 k

Ω

each or by connecting the output of an operational amplifier that is

outputting the reference voltage. If the external resistor divider is

used, place a 0.01

µF ceramic bypass capacitor between the

new reference voltage when the external resistor divider is used will

be about 0.5 percent PLUS the sum of the tolerances of the

resistors used in the divider.

Please note that when the NE57810 is operating in this fashion, the

power dissipation of the part may increase.

SL01679

ExtRefIn

RefOut

NE57810

EXTERNAL REFERENCE IN

GND

(LF)

(HF)

GND

Figure 13.