User's Manual

TRF7960
TRF7961
www.ti.com SLOU186F–AUGUST 2006–REVISED AUGUST 2010
Table 5-3. Supply-Regulator Setting – Automatic – 5-V System
Byte Option Bits Setting in Control Register Action
Address
B7 B6 B5 B4 B3 B2
(1)
B1 B0
00 1 5-V system
0B 1 x 1 1 Automatic regulator setting ≉ 250-mV difference
0B 1 x 1 0 Automatic regulator setting ≉ 350-mV difference
0B 1 x 0 0 Automatic regulator setting ≉ 400-mV difference
(1) X are don't cares
Table 5-4. Supply-Regulator Setting – Automatic – 3-V System
Byte Option Bits Setting in Control Register Action
Address
B7 B6 B5 B4 B3 B2
(1)
B1 B0
00 0 3-V system
0B 1 x 1 1 Automatic regulator setting ≉ 250-mV difference
0B 1 x 1 0 Automatic regulator setting ≉ 350-mV difference
0B 1 x 0 0 Automatic regulator setting ≉ 400-mV difference
(1) X are don't cares
5.1.4 Power Modes
The chip has seven power states, which are controlled by two input pins (EN and EN2) and three bits in
the chip status control register (00h).
The main reader enable input is EN (which has a threshold level of 1 V minimum). Any input signal level
from 1.8 V to V
IN
can be used. When EN is set high, all of the reader regulators are enabled, together with
the 13.56-MHz oscillator, while the SYS_CLK (output clock for external micro controller) is made available.
The auxiliary-enable input EN2 has two functions. A direct connection from EN2 to V
IN
ensures availability
of the regulated supply (V
DD_X
) and an auxiliary clock signal (60 kHz) on the SYS_CLK output (same for
the case EN = 0). This mode is intended for systems in which the MCU controlling the reader is also being
supplied by the reader supply regulator (V
DD_X
) and the MCU clock is supplied by the SYS_CLK output of
the reader. This allows the MCU supply and clock to be available during power-down.
A second function of the EN2 input is to enable start-up of the reader system from complete power down
(EN = 0, EN2 = 0). In this case the EN input is being controlled by the MCU or other system device that is
without supply voltage during complete power down (thus unable to control the EN input). A rising edge
applied to the EN2 input (which has a 1-V threshold level) starts the reader supply system and 13.56-MHz
oscillator (identical to condition EN = 1). This start-up mode lasts until all of the regulators have settled
and the 13.56-MHz oscillator has stabilized. If the EN input is set high by the MCU (or other system
device), the reader stays active. If the EN input is not set high within 100 μs after the SYS_CLK output is
switched from auxiliary clock (60 kHz) to high-frequency clock (derived from the crystal oscillator), the
reader system returns to complete power-down mode. This option can be used to wake the reader system
from complete power down by using a push-button switch or by sending a single pulse.
Copyright © 2006–2010, Texas Instruments Incorporated System Description 13
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