P4022 Datasheet, PDF (4/13 Pages) EM Microelectronic - MARIN SA – Multi Frequency Contactless Identification Device Anti-Collision compatible with BTGs Supertag Category Protocols

PRELIMINARY
EM MICROELECTRONIC-MARIN SA P4022
Current Consumption
The total typical current consumption from the
storage capacitor CP in various modes is shown in
Table 4 below.
The total current consumption in conjunction with
the size of the power storage capacitance
determines the maximum time that transistor Q2
can be turned on and Q1 turned off, before the
supply voltage drops below 1 V, thereby resulting
in the power-on reset block resetting the chip.
This in turn determines the minimum data bit rate
and maximum range. Similarly the total storage
capacitance and total current determine the
maximum unpowered SWITCHED-OFF state time.
The second column shows the current drawn in
FREE-RUNNING mode. The third column shows
the current drawn for the bi-directional protocols,
which includes the current drawn by the GAP
input pull-up. The fourth column shows the total
current drawn in SWITCHED-OFF state. In this
mode both the GAP input and the shunt regulator
draws current from the storage capacitor.
Supply
(V)
Current
(Free)
(µA)
Current
(Bi-directional)
(µA)
Current
(SWTICHED-
OFF state)
(µA)
1.0
1.8
2.2
2.8
1.2
2.6
3.6
4.6
1.5
3.8
6.3
8.3
2.0
6
13
16
3.0
11
31
51
Table 4
Table 5 below shows the theoretical storage
capacitance required for various applications.
For free-running applications, the capacitance
required is determined by the data bit rate and
encoding method. Only the Logic, PON and
oscillator draw current in Free-running
applications. For the bi-directional protocols, the
GAP input pull-up also draws current during
modulation.
Data bit En-
rate coding
(kbit/s)
Free-
running
(pF)
Bi-direc-
tional
(pF)
Counting
(µF)
4
Man
2700
3600
20
4
Glitch
670
900
20
64
Man
170
240
20
64 Glitch
40
80
20
Table 5
For counting applications (SWITCH-OFF BTG-
Supertag) the required unpowered time in the
SWITCHED-OFF state determines the size of the
capacitor. In applications where the chip can be
guaranteed to stay powered, the capacitor size is
determined by the data bit rate.
It should be noted that the on-chip capacitance is
sufficient for free-running applications at 64 kbit/s,
while inductive applications at 4 kbit/s require a
few nanofarad externally. Unpowered counting
applications will require more than 20 µF to
achieve 1 second unpowered time in the
SWITCHED-OFF state.
4