EM4095
Signal RDY/CLK
This signal provides the external microprocessor with
clock signal which is synchronous with the signal on ANT1
and with information about EM4095 internal state. Clock
signal synchronous with ANT1 indicates that PLL is in lock
and that Reception chain operation point is set. When
SHD is high RDY/CLK pin is forced low. After high to low
transition on SHD the PLL starts-up, and the reception
chain is switched on. After time T
SET
the PLL is locked and
reception chain operation point has been established. At
this moment the same signal which is being transmitted to
ANT1 is also put to RDY/CLK pin indicating to
microprocessor that it can start observing signal on
DEMOD_OUT and giving at the same time reference
clock signal. Clock on RDY/CLK pin is continuous, it is
also present during time the ANT drivers are OFF due to
high level on MOD pin. During the time T
SET
from high to
low transition on SHD pin RDY/CLK pin is pulled down by
100 kΩ pull down resistor. The reason for this is in
additional functionality of RDY/CLK pin in case of AM
modulation with index which is lower then 100%. In that
case it is used as auxiliary driver which maintains lower
amplitude on coil during modulation. (see also Typical
Operating Configuration)
Remark: Please refer to AN4095 for external components
calculation and limits.
Typical Operating Configuration
Read Only Mode
RDY/CLK
1
2
3
16
15
14
Read/Write mode (High Q factor antenna)
RDY/CLK
1
16
15
14
R
SER
+5V
L
A
C
RES
C
DV1
C
DV2
+5V
2
3
4
5
6
7
8
C
DC2
C
FCAP
SHD
DEMOD_OUT
MOD
C
AGND
C
DEC
P4095
EM4095
12
11
10
9
13
µP
Fig. 8
Read/Write mode (AM modulation)
RDY/CLK
R
AM
+5V
1
2
3
16
15
14
C
DC2
C
FCAP
SHD
DEMOD_OUT
MOD
C
AGND
C
DEC
L
A
C
RES
C
DV1
C
DV2
4
5
EM4095
13
P4095
12
11
10
9
µP
+5V
6
7
8
Fig. 9
C
DC2
C
FCAP
SHD
DEMOD_OUT
MOD
C
AGND
C
DEC
Figure 6 presents EM4095 used in Read Only mode. Pin
MOD is not used. It is recommended to connect it to VSS.
+5V
L
A
C
RES
C
DV1
C
DV2
+5V
4
5
6
7
8
P4095
EM4095
13
12
11
10
9
µP
Figure 7 presents typical R/W configuration for OOK
communication protocol reader to transponder (eg.
EM4150). It is recommended to be used with low Q factor
antennas (up to 15).
When the antenna quality is high using configuration of
figure 6 or 7 the voltage on antenna can arrive in the
range of few hundred volts and antenna peak current may
exceed its maximum value. In such a case the capacitive
divider ratio has to be high thus limiting the sensitivity. For
such case it is better to reduce antenna circuit quality by
adding serial resistor. In this way the antenna current is
lower and thus power dissipation of IC is reduced with
practically the same performance (Fig. 8).
In the case AM modulation communication protocol
reader to transponder (eg. EM4069) is needed a single
ended configuration has to be used (figure 9). When pin
MOD is pulled high driver on ANT1 is put in three state,
driver RDY/CLK continues driving thus maintaining lower
antenna current. Modulation index is adjusted by resitor
R
AM
. As mentioned above RDY/CLK signal becomes
active only after the demodulation chain operating point is
set.
Before it is pulled down by high impedance pull down
resistor (100 kΩ) in order not to load ANT1 output. In the
case of AM modulation configuration the total antenna
current change at the moment RDY/CLK pin becomes
active, so external microprocessor has to wait another
T
SET
before it can start observing DEMOD_OUT.
7
www.emmicroelectronic.com
Fig. 6
Read/Write mode (Low Q factor antenna)
RDY/CLK
1
2
3
16
15
14
C
DC2
C
FCAP
SHD
DEMOD_OUT
MOD
C
AGND
C
DEC
+5V
L
A
C
RES
C
DV1
C
DV2
+5V
4
5
6
7
8
P4095
EM4095
13
12
11
10
9
µP
Fig. 7
Copyright
2002, EM Microelectronic-Marin SA
EMMICRO [ EM MICROELECTRONIC - MARIN SA ]
