
000-0046140-111
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SLG46140
22.0 Power On Reset (POR)
The SLG46140 has a power-on reset (POR) macrocell to ensure correct device initialization and operation of all macrocells in
the device. The purpose of the POR circuit is to have consistent behavior and predictable results when the VDD power is first
ramping to the device, and also while the VDD is falling during power-down. To accomplish this goal, the POR drives a defined
sequence of internal events that trigger changes to the states of different macrocells inside the device, and finally to the state of
the I/O pins.
22.1 General Operation
The SLG46140 is guaranteed to be powered down and nonoperational when the VDD voltage (voltage on PIN1) is less than
Power Off Threshold (see in Electrical Characteristics table), but not less than -0.6V. Another essential condition for the chip to
be powered down is that no voltage higher (see Note 1) than the VDD voltage is applied to any other PIN. For example, if VDD
voltage is 0.3V, applying a voltage higher than 0.3V to any other PIN is incorrect, and can lead to incorrect or unexpected device
behavior.
Note 1. There is a 0.6V margin due to forward drop voltage of the ESD protection diodes.
To start the POR sequence in the SLG46140, the voltage applied on the VDD should be higher than the Power_ON threshold
(see Note 2). The full operational VDD range for the SLG46140 is 1.71V – 5.5V (1.8V ±5% - 5V±10%). This means that the VDD
voltage must ramp up to the operational voltage value, but the POR sequence will start earlier, as soon as the VDD voltage rises
to the Power_ON threshold. After the POR sequence has started, the SLG46140 will have a typical period of time to go through
all the steps in the sequence (see
and
), and will be ready and completely operational after the POR sequence
is complete.
Note 2. The Power_ON threshold is defined in Electrical Characteristics table.
Note 3. VDD ramp rising speed must be less than 0.6 V/µs after power on. Violating this specification may cause chip to restart.
To power down the chip the VDD voltage should be lower than the operational and to guarantee that chip is powered down it
should be less than Power Off Threshold.
All PINs are in high impedance state when the chip is powered down and while the POR sequence is taking place. The last step
in the POR sequence releases the I/O structures from the high impedance state, at which time the device is operational. The pin
configuration at this point in time is defined by the design programmed into the chip. Also as it was mentioned before the voltage
on PINs can’t be bigger than the VDD, this rule also applies to the case when the chip is powered on.