mfrc522 NXP Semiconductors, mfrc522 Datasheet - Page 71

• Manufacturer Part Number: mfrc522
• Description: Contactless Reader Ic
• Manufacturer: NXP Semiconductors

NXP Semiconductors
17. Reset and Oscillator Startup Time
112132
Product data sheet
17.1 Reset Timing Requirements
17.2 Oscillator Startup Time
The reset signal is filtered by a hysteresis circuit and a spike filter (rejects signals shorter
than 10 ns) before it enters the digital circuit. In order to perform a reset, the signal has to
be low for at least 100 ns.
Having set the MFRC522 to a Power-down mode or supplying the IC with XVDD the
following figure describes the startup timing for the oscillator.
The time t
startup time is defined by the crystal itself.
The t
before the MFRC522 can be addressed. The delay time is calculated as follows:
t
The time t
delay
Device Activation
Fig 23. Oscillator Startup time.
Clock Stable
Clock Ready
delay
[μs] = 1024/27.12 = 37.76 μs.
Oscillator
defines the internal delay time of the MFRC522 when the clock signal is stable
startup
osc
is defined as the sum of the time t
defines the startup time of crystal oscillator circuit. The crystal oscillator
Rev. 3.2 — 22 May 2007
t startup
t osc
delay
and t
startup
.
Contactless Reader IC
MFRC522
© NXP B.V. 2007. All rights reserved.
t delay
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t