IGLOO Low-Power Flash FPGAs with Flash*Freeze Technology
3- 4
A dvanced v0. 1
I/O Power-Up and Supply Voltage Thresholds for Power-On Reset (Commercial and
Industrial)
Sophisticated
power-up
management
circuitry
is
designed into every IGLOO device. These circuits ensure
easy transition from the powered-off state to the
powered-up state of the device. The many different
supplies can power up in any sequence with minimized
current spikes or surges. In addition, the I/O will be in a
known state through the power-up sequence. The basic
There are five regions to consider during power-up.
IGLOO I/Os are activated only if ALL of the following
three conditions are met:
1. VCC and VCCI are above the minimum specified trip
2. VCCI > VCC – 0.75 V (typical)
3. Chip is in the operating mode.
VCCI Trip Point:
Ramping up: 0.6 V < trip_point_up < 1.2 V
Ramping down: 0.5 V < trip_point_down < 1.1 V
VCC Trip Point:
Ramping up: 0.6 V < trip_point_up < 1.1 V
Ramping down: 0.5 V < trip_point_down < 1 V
VCC and VCCI ramp-up trip points are about 100 mV
higher than ramp-down trip points. This specifically
built-in
hysteresis
prevents
undesirable
power-up
oscillations and current surges. Note the following:
During programming, I/Os become tristated and
weakly pulled up to VCCI.
JTAG supply, PLL power supplies, and charge pump
VPUMP supply have no influence on I/O behavior.
Internal Power-Up Activation Sequence
1. Core
2. Input buffers
3. Output buffers, after 200 ns delay from input
buffer activation
To make sure the transition from input buffers to output
buffers is clean, ensure that there is no path longer than
100 ns from input buffer to output buffer in your
design.
Figure 3-1
I/O State as a Function of VCCI and VCC Voltage Levels
Region 1: I/O buffers are OFF
Region 2: I/O buffers are ON.
I/Os are functional (except differential inputs)
but slower because V
CCI
/V
CC
are below
specification. For the same reason, input
buffers do not meet V
IH
/V
IL
levels, and
output buffers do not meet V
OH
/V
OL
levels.
Min V
CCI datasheet specification
voltage at a selected I/O
standard; i.e., 1.425 V or 1.7 V
or 2.3 V or 3.0 V
VCC
VCC = 1.425 V
Region 1: I/O Buffers are OFF
Activation trip point:
Va = 0.85 V ± 0.25 V
Deactivation trip point:
Vd = 0.75 V ± 0.25 V
Activation trip point:
Va = 0.9 V ± 0.3 V
Deactivation trip point:
Vd = 0.8 V ± 0.3 V
VCC = 1.575 V
Region 5: I/O buffers are ON
and power supplies are within
specification.
I/Os meet the entire datasheet
and timer specifications for
speed, V
IH
/V
IL
, V
OH
/V
OL
, etc.
Region 4: I/O
buffers are ON.
I/Os are functional
(except differential
but slower because V
CCI is
below specification. For the
same reason, input buffers do not
meet V
IH
/V
IL
levels, and output
buffers do not meet V
OH
/V
OL
levels.
Region 4: I/O
buffers are ON.
I/Os are functional
(except differential inputs)
where VT can be from 0.58 V to 0.9 V (typically 0.75 V)
VCCI
Region 3: I/O buffers are ON.
I/Os are functional; I/O DC
specifications are met,
but I/Os are slower because
the V
CC
is below specification.
V
CC = VCCI + VT