Power Sequence Auto Start Using Altera MAX Series
2014.09.22
AN-491
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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 features.
Related Information
• Design Example for MAX II
Provides the MAX II design files for this application note (AN 491).
• Design Example for MAX 10
Provides the MAX 10 design file for this application note (AN 491).
• Power Management in Portable Systems Using MAX II CPLDs
• MAX II CPLD Design Guidelines
Power Saving
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.
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Figure 1: Basic Block Diagram of an Auto Start System
Altera Device
Power Supply
External
Circuit
power_dwn
power_dwn_inv
'Memory' capacitors
connected to
bi-directional ports
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.
Auto Start
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 consump‐
tion.
2
Auto Start
AN-491
2014.09.22
Altera Corporation
Power Sequence Auto Start Using Altera MAX Series
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