EP3C55 datasheet(9/34 Pages) ALTERA

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Chapter 1: Cyclone III Device Data Sheet

1–9

Electrical Characteristics

Altera Corporation

Cyclone III Device Handbook, Volume 2

Example 1–1 shows you the example to calculate the change of 50

Ω I/O impedance

from 25°C at 3.0 V to 85°C at 3.15 V:

Pin Capacitance

Table 1–9 lists the pin capacitance for Cyclone III devices.

Example 1–1.

ΔR

V = (3.15 – 3) × 1000 × –0.026 = –3.83

ΔR

T = (85 – 25) × 0.262 = 15.72

Because

ΔR

V is negative,

V = 1 / (3.83/100 + 1) = 0.963

Because

ΔR

T is positive,

T = 15.72/100 + 1 = 1.157

MF = 0.963 × 1.157 = 1.114

final = 50 × 1.114 = 55.71

Table 1–9. Cyclone III Devices Pin Capacitance

Symbol

Parameter

Typical –

QFP

Typical –

FBGA

Unit

IOTB

Input capacitance on top/bottom I/O pins

IOLR

Input capacitance on left/right I/O pins

LV DSLR

Input capacitance on left/right I/O pins with dedicated

LVDS output

V REFLR (1)

Input capacitance on left/right dual-purpose VREF pin

when used as V

REF or user I/O pin

V REFTB (1)

Input capacitance on top/bottom dual-purpose VREF pin

when used as V

REF or user I/O pin

23 (2)

CLKTB

Input capacitance on top/bottom dedicated clock input

pins

CLKLR

Input capacitance on left/right dedicated clock input pins

Notes to Table 1–9:

(1) When VREF pin is used as regular input or output, a reduced performance of toggle rate and tCOis expected due to

higher pin capacitance.

(2) CVREFTB for EP3C25 is 30 pF.

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