BD3531F

2/15

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TSZ22111・15・001

TSZ02201-0J2J0A900950-1-2

02.Nov.2015 Rev.001

Pin Configuration

Pin Descriptions

Description of Blocks

1.

VCC

The VCC pin is for the independent power supply input that operates the internal circuit of the IC. It is the voltage at

this pin that drives the IC’s amplifier circuits. The VCC input ranges 5V and maximum current consumption is 4mA. A

bypass capacitor of 10

μF or so should be connected to this pin when using the IC in an application circuit.

2.

VDDQ

This is th

e power supply input pin for an internal voltage divider network. The voltage at VDDQ is halved by two 50kΩ

internal voltage-divider resistors and the resulting voltage serves as reference for the VTT output. Since VTT =

1/2VDDQ, the JEDEC requirement for DDR-SDRAM can be satisfied by supplying the correct voltage to VDDQ.

Noise input should be avoided at the VDDQ pin as it is also included by the voltage-divider at the output. An RC filter

consisting of a resistor and a capacitor (220Ω and 2.2μF, for instance,) may be used to reduce the noise input but

make sure that it will not significantly affect the voltage-

divider’s output.

3.

VTT_IN

VTT_IN is the

power supply input pin for the VTT output. Input voltage may range from 1.0V to 5.5V, but

consideration must be given to the current limit dictated by the ON-Resistance of the IC and to the change in allowable

loss due to input/output voltage difference.

Generally, the following voltages are supplied:

・ DDR I

・ DDRII

Take note that a high-impedance voltage input at VTT_IN may result in oscillation or degradation in ripple rejection, so

connecting a 100

μF capacitor with minimal change in capacitance to VTT_IN terminal is recommended. However,

this impedance may depend on the characteristics of the power supply input and the impedance of the PC board wiring,

which must be carefully checked before use.

4.

VREF

BD3531F provides a constant voltage, VREF, which is independent from the VTT output and can serve as reference

input for memory c

ontrollers and DRAMs. The voltage level of VREF is kept constant even if the EN pin is at “Low”

level, making the use of this IC compatible with the “Self Refresh” state of DRAMs.

In order to stabilize the output voltage, connecting the correct combination of capacitor and resistor to VREF is

necessary. For this purpose, a combination of 1.0μF to 2.2μF ceramic capacitor, characterized by minimal variation in

capacitance, and a 0.5Ω to 2.2Ω phase compensating resistor is recommended.

5.

VTTS

VTTS is a sense pin for the load regulation of the VTT output voltage. In case the wire connecting VTT pin and the load

is too long, connecting VTTS pin to the part of the wire nearer to the load may improve load regulation.

Pin No.

Pin Name

Pin Function

1

GND

GND Pin

2

EN

Enable Input Pin

3

VTTS

Detector Pin for Termination Voltage

4

VREF

Reference Voltage Output Pin

5

VDDQ

Reference Voltage Input Pin

6

VCC

VCC Pin

7

VTT_IN

Termination Input Pin

8

VTT

Termination Output Pin

VTT_IN

GND

EN

VTTS

VREF

VTT

VCC

VDDQ

1

2

3

4

5

6

7

8

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