This design example describes a simple method for
implementing Auto Start using Altera® MAX® II, MAX V, and MAX 10 devices.
The supported Altera devices are an excellent choice
for implementing low power applications and when battery life
extension are of importance. These devices are well suited for this
technique because of their simple power sequencing and proprietary
Many consumer and industrial application systems do not require the
device to be powered on at all times. It is preferred to have a design in
which the device powers on intermittently, remaining off for most of the
cycle. This is especially useful in portable battery-operated systems
which can function on a non-continuous periodic task.
Because MAX II and MAX V devices do not require a special power-on sequence, they
can be switched on quickly (typically 200 μs, depending on the logic
density). The ability to switch on and off quickly allows you to completely
switch off the device and switch it back on using external circuitry. The
external circuitry can be a simple RC timer designed for the required
delay. The MAX 10 Single Supply devices are designed for customer to easily manage power-up sequence on the board. The instant-on
feature is the fastest power-up mode for MAX 10 devices.
However, if you implement considerable power off time, such a simple
RC timer circuit is not practical. This requires very large values of R & C.
A counter utilizing capacitors as memory elements extends the
power-down period. The device turns on for a very small duration during
this power-down period, reads the value in these capacitors, increments
the count, and stores them back again before powering down. This cycle
repeats itself until the desired count is reached, at which time the device
switches on completely. When it switches on in the power-on period, the
device executes the task it was designed to accomplish.
Figure 1. Basic Block Diagram of an Auto Start System
The device uses the power down signals (power_dwn and its
complement) to trigger the external circuit and power down the device.
After the designed delay, the external circuit powers on the device. The
memory capacitors are connected to the bidirectional pins of the device
and are used as non-volatile memory elements.
As soon as the device is powered on, it goes into the read state.
The value on the capacitors is read and stored in registers. This
implementation uses two capacitors that allow you to store four different
values. One of the four LEDs used is switched on after the read operation
that corresponds to the value read from the capacitors. This value or
count is incremented and stored back into the capacitors, which act as
non-volatile memory elements. Power down is then initiated by setting
the power_dwn pin high. When power down is complete, the external RC
circuit acts as a timer and activates the device. This is repeated until the
desired delay is obtained (desired count is reached) and the complete
effective stretching of the power-down time is achieved (four times in this
case). The duty cycle of operation of the device can be controlled, resulting
in a longer power-down period and thereby decreasing the overall power
Figure 2. Auto Start Operation Flowchart
Figure 3. Power Cycle Waveform
Each cycle consists of a
‘Power On’ and a ‘Power Down’ period. In the ‘Power Down’ period the
MAX II devices regularly switches on for a very small period of time ‘t’, increments
the counter, and switches off. When the desired count is reached, the
MAX II devices enter into the Power On period and reinitializes the value of the
counter. It then performs the desired functions. At the end of the ‘Power
On’ period, the capacitors contain the reinitialized value. When the MAX II devices
are powered on again, it increments the counter and shuts down after the
period ‘t’, and the count is restarted.
Figure 4. External Circuitry
When the power_dwn
signal is low (pwr_dwn_inv is high), the voltage regulator (which has an
active low shutdown control) is switched on and the capacitor C
discharges. Whenever the device wants to switch off, it makes the
power_dwn signal high (pwr_dwn_inv is low). This switches off the
voltage regulator, cutting off the power to the device.
When all the I/O pins of the device are tri-stated, the capacitor starts
charging. It charges until the voltage across the device remains less than
the threshold potential of the regulator’s shutdown control (enhanced by
diodes D1 and D2), When the threshold is exceeded, the voltage regulator
is switched on. The cycle repeats itself.
Auto Start Using MAX II Devices
The detailed description of the implementation is based on the MAX II devices. This application can also be implemented in
MAX V and MAX 10 devices.
You can implement this design example with an EPM240 or any other device, supporting external RC circuitry, a power supply
capable of shut down, and two capacitors on the GPIO pins to act as
‘memory’ devices that save previous states. Implementation involves
using the design example source code and allocating the appropriate
signals and control lines to the GPIO lines of the MAX II device, along
with its support circuitry. The MDN-B2 demo board has a built-in
To demonstrate the control of the power cycle, two capacitors (C9 and
C10 on the MDN-B2 demo board) and four LEDs (D2, D3, D5, and D6) are
used. This design reads the values from the capacitors as soon as the
MAX II is powered on.
Table 1. LED Mapping
For each set of values, the corresponding LED glows. The MAX II then
increments the count and writes back this value to the capacitors. The
write cycle continues for some time to ensure sufficient charging of the
capacitors. The power down and its complement signals are made high
and low, respectively, resulting in complete power down.
Upon subsequent power on after a period of time determined by the
external RC, the MAX II repeats the cycle of reading, LED display,
and updating the capacitor states before powering down again.
Observing the LED counting up demonstrates the Auto Start feature of
Table 2. EPM240G Pin Assignments. Assign unused pins As input tri-stated in the Device and Pin
Options dialog box in the Quartus II software prior to compilation.
Auto Start Design Demonstration on MDN-B2 Board
To demonstrate the design example on the MDN-B2 demo board, follow these steps:
Ensure that VCCIO voltages on both banks are set to 2.5V (jumpers on
JP9 and JP7 on the demo board are set to 2.5V).
Turn on the power to the demo board (using slide switch SW1) and
download the design on to the MAX II device through the JP5 JTAG
header and a conventional programming cable such as the
ByteBlaster™ II or USB-Blaster™.
Keep SW4 on the board pressed as
you begin the programming process.
Turn off power to the board and
remove the JTAG connector after programming.
Turn on the power to the demo board. Using a voltmeter between
TP3 and GND on the demo board, observe VCCINT being powered
down and powered up cyclically.
Repeat observation for VCCIO
(between TP1 and GND on demo board). Also observe the 4 LEDs
(D2, D3, D5, and D6) shift their position each time the power to the
device is restored.
Each time the LED blinks, its position is based
upon the previous LED position that blinked and in accordance to
the LED Mapping table.
Design example adapted for Altera MAX 10 FPGAs by:
Orchid Technologies Engineering and Consulting, Inc.