OTB25LPLL datasheet(14/174 Pages) ACTEL

14 / 174 page

ProASICPLUS Flash Family FPGAs

1- 10

v5.2

Power-Up Sequencing

While ProASICPLUS devices are live at power-up, the order

of VDD and VDDP power-up is important during system

start-up. VDD should be powered up simultaneously with

VDDP on ProASIC

PLUS devices. Failure to follow these

guidelines may result in undesirable pin behavior during

system start-up. For more information, refer to Actel’s

Power-Up Behavior of ProASICPLUS Devices application

note.

LVPECL Input Pads

In addition to standard I/O pads and power pads,

ProASICPLUS devices have a single LVPECL input pad on

both the east and west sides of the device, along with

AVDD and AGND pins to power the PLL block. The

LVPECL pad cell consists of an input buffer (containing a

low voltage differential amplifier) and a signal and its

complement, PPECL (I/P) (PECLN) and NPECL (PECLREF).

The LVPECL input pad cell differs from the standard I/O

cell in that it is operated from VDD only.

Since it is exclusively an input, it requires no output

signal, output enable signal, or output configuration

bits. As a special high-speed differential input, it also

does not require pull ups. Recommended termination for

LVPECL inputs is shown in Figure 1-10. The LVPECL pad

cell compares voltages on the PPECL (I/P) pad (as

illustrated in Figure 1-11) and the NPECL pad and sends

the results to the global MUX (Figure 1-14 on page 1-14).

This high-speed, low-skew output essentially controls the

clock conditioning circuit.

LVPECLs are designed to meet LVPECL JEDEC receiver

standard levels (Table 1-5).

Figure 1-10 • Recommended Termination for LVPECL Inputs

Figure 1-11 • LVPECL High and Low Threshold Values

Table 1-5 •

LVPECL Receiver Specifications

Symbol

Parameter

Min.

Max

Units

VIH

Input High Voltage

1.49

2.72

VIL

Input Low Voltage

0.86

2.125

VID

Differential Input Voltage

0.3

VDD

PPECL

NPECL

From LVPECL Driver

Data

Z = 50

Ω

Z = 50

Ω

R = 100

Ω

2.72

2.125

1.49

0.86

Voltage

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