EM6621
3. Power Supply
The EM6621 is supplied by a single external power supply between V
DD
(Vbat) and V
SS
(Ground). A built-in
voltage regulator generates Vreg providing regulated voltage for the oscillator and the internal logic. The output
drivers are supplied directly from the external supply V
DD
. The internal power configuration is shown below in
Figure 5.
To supply the internal core logic it is possible to use either the internal voltage regulator (Vreg < V
DD
) or Vbat
directly ( Vreg = V
DD
). The selection is done by metal 1 mask option. By default the voltage regulator is used.
Refer to chapter 18.1.5 for the metal mask selection.
The internal voltage regulator is chosen for high voltage systems. It saves power by reducing the internal core
logic’s power supply to an optimum value. However, due to the inherent voltage drop over the regulator the
minimal V
DD
is restricted to 1.4 V .
A direct Vbat connection can be selected for systems running on a 1.5 V battery. The internal 1 KOhm resistor
together with the external capacitor on Vreg is filtering the V
DD
supply to the internal core. In this case the
minimum V
DD
can be as low as 1.2 V.
Figure 5. Internal Power Supply
T erm inal
V bat
M V reg
M 1B
1kO hm
M 1A
Term inal
V reg
A ll P ad
input &
output
buffers,
S V LD
R ef. Logic
C ore Logic,
LC D Logic,
O scillator
V oltage m ultiplier,
LC D outputs
R ef. LC D
03/02 REV. D/444
Copyright
2002, EM Microelectronic-Marin SA
7
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EMMICRO [ EM MICROELECTRONIC - MARIN SA ]
