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APPLICATION INFORMATION

Typical DDR Application Diagram

Inhibit

+

+

DDRII/

QDRII

PTH05010W

VDDQ I/O Memory

Inhibit

+

PTH05050Y

DDR Termination

+

2 ×

330 µF

2 ×

22 µF

2 ×

330 µF

2 ×

22 µF

+Sense

Margin ±

Auto-Track

1 kΩ

1 kΩ

220 µF

47 µF

470 µF

47 µF

5.51 kΩ

UDG−05096

CAPACITOR RECOMMENDATIONS FOR THE PTH03010Y AND PTH05010Y DDR POWER

Input Capacitor

Output Capacitors

PTH03010Y

PTH05010Y

PTH12010Y

SLTS223A–MARCH 2004–REVISED OCTOBER 2005

MODULES

(3.3-V/5-V OPTION)

The recommended input capacitor(s) is determined by the 470 µF minimum capacitance and 500 mArms

minimum ripple current rating.

Ripple current, less than 160 mΩ equivalent series resistance (ESR), and temperature are the major

considerations when selecting input capacitors. Unlike polymer tantalum, regular tantalum capacitors have a

recommended minimum voltage rating of 2 × (maximum dc voltage + ac ripple). This is standard practice to

ensure reliability.

For improved ripple reduction on the input bus, ceramic capacitors may used to complement electrolytic types to

achieve the minimum required capacitance.

For applications with load transients (sudden changes in load current), regulator response benefits from external

output capacitance. The recommended output capacitance of 470 µF will allow the modue to meet its transieint

response specification. (See Electrical Specifications table). For most applications, a high quality computer-grade

aluminum electrolytic capacitor is adequate. These capacitors provide decoupling over the frequency range,

2 kHz to 150 kHz, and are suitable for ambient temperatures above 0°C. Below 0°C, tantalum, ceramic or

Os-Con type capacitors are recommended. When using one or more nonceramic capacitors, the calculated

equivalent ESR should be no lower than 4 mΩ (7 mΩ using the manufacturer’s maximum ESR for a single

capacitor).

a 10-µF to 22-µF X5R/X7R ceramic capacitor to the output reduces the output ripple voltage and improve the

regulator’s transient response. The measurement of both the output ripple and transient response is also best

achieved across a 10-µF ceramic capacitor.

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