EPM240 Datasheet, PDF (56/86 Pages) Altera Corporation – JTAG & In-System Programmability

4–6
Chapter 4: Hot Socketing and Power-On Reset in MAX II Devices
Power-On Reset Circuitry
Power-Up Characteristics
When power is applied to a MAX II device, the POR circuit monitors V_CCINT and
begins SRAM download at an approximate voltage of 1.7 V or 1.55 V for MAX IIG and
MAX IIZ devices. From this voltage reference, SRAM download and entry into user
mode takes 200 to 450 µs maximum, depending on device density. This period of time
is specified as t_CONFIG in the power-up timing section of the DC and Switching
Characteristics chapter in the MAX II Device Handbook.
Entry into user mode is gated by whether all V_CCIO banks are powered with sufficient
operating voltage. If V_CCINT and V_CCIO are powered simultaneously, the device enters
user mode within the t_CONFIG specifications. If V_CCIO is powered more than t_CONFIG after
V_CCINT, the device does not enter user mode until 2 µs after all V_CCIO banks are powered.
For MAX II and MAX IIG devices, when in user mode, the POR circuitry continues to
monitor the V_CCINT (but not V_CCIO) voltage level to detect a brown-out condition. If
there is a V_CCINT voltage sag at or below 1.4 V during user mode, the POR circuit resets
the SRAM and tri-states the I/O pins. Once V_CCINT rises back to approximately 1.7 V
(or 1.55 V for MAX IIG devices), the SRAM download restarts and the device begins
to operate after t_CONFIG time has passed.
For MAX IIZ devices, the POR circuitry does not monitor the V_CCINT and V_CCIO voltage
levels after the device enters user mode. If there is a V_CCINT voltage sag below 1.4 V
during user mode, the functionality of the device will not be guaranteed and you
must power down the V_CCINT to 0 V for a minimum of 10 µs before powering the V_CCINT
and V_CCIO up again. Once V_CCINT rises from 0 V back to approximately 1.55 V, the
SRAM download restarts and the device begins to operate after t_CONFIG time has
passed.
Figure 4–5 shows the voltages for POR of MAX II, MAX IIG, and MAX IIZ devices
during power-up into user mode and from user mode to power-down or brown-out.
1 All V_CCINT and V_CCIO pins of all banks must be powered on MAX II devices before
entering user mode.
MAX II Device Handbook
© October 2008 Altera Corporation