pc87591l National Semiconductor Corporation, pc87591l Datasheet - Page 64

• Manufacturer Part Number: pc87591l
• Description: Lpc Mobile Embedded Controllers
• Manufacturer: National Semiconductor Corporation

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3.0 Power, Reset and Clocks
Both AV
erated with only one of them (AV
cause current leakage. Therefore, ADC and DAC modules should be left at their reset condition (disabled) or disabled by
firmware until AV
to be externally filtered or driven by a low-noise power supply.
The PC87591x is designed to operate with a Lithium backup battery that supplies voltage up to 3.6V. The PC87591x includes
an internal current-limiting resistor on the V
V
AV
modules from noise caused by the digital modules.
The following directives are recommended for the PC87591x power and ground connections (see Figure 11 for the power
supply connections):
Ground Connection
Use two ground planes, one for the digital signals (GND) and one for the analog signals (AGND). The following ground con-
nections should also be made:
Note that low-impedance ground layers improve noise isolation and reduce ground bounce problems.
Power Connection
All PC87591x supply pins must be connected to the appropriate power plane, and decoupling capacitors must be used as
recommended below.
The analog supply pin, AV
supply (3.3V). If the AV
LC or RC filter for the AV
by replacing L
Decoupling Capacitors
The following decoupling capacitors should be used to reduce power supply deeps, ground bounce and EMI (refer to
Figure 11 for the position of capacitors, e.g., C1, C2, etc.):
DD
CC
The analog ground plane (AGND) should be connected at only one point to the digital ground plane (GND). This point
should be located physically near the PC87591x.
The analog ground return pin of the PC87591x (AGND) should be connected to the analog ground plane.
The decoupling capacitors of the analog supply (AV
as possible to the AGND pin.
The ground reference of the voltage input signals to the ADC module (V
the AGND plane close to the PC87591x.
The ground reference of the voltage output signals from the DAC module (V
to the AGND plane close to the PC87591x.
All GND pins of the PC87591x must be connected to the GND plane.
The decoupling capacitors of the Suspend digital supply (V
one side of each capacitor should be connected to the ground plane.
The ground reference of the voltage input signals to the ACM module (KBV
to the GND plane close to the PC87591x.
The decoupling capacitors of the Host digital supply (V
each capacitor should be connected to the ground plane.
The ground return and the decoupling capacitor of the backup battery supply (V
PC87591x; one of the capacitor’s sides should be connected to the ground plane.
Suspend digital supply (V
pin pair. Also, place one 10 47 F C
Host digital supply (V
pair. Also, place one 10-47 F tantalum capacitor (C6) on the common net as close as possible to the chip.
Backup battery (V
Analog supply (AV
close as possible to the pin.
, V
use a separate ground return, named analog ground and marked AGND. This ensures effective isolation of the analog
CC
CC
and V
and V
1
(in Figure 11) with a 10 resistor (not shown in the figure).
BAT
CC
CC
is within the limits specified above. In addition, the AV
use a common ground return, named digital ground and marked GND. The analog circuits supplied by
should be applied for correct operation; and although the PC87591x is protected against damage if op-
BAT
CC
CC
CC
): Place one 0.1 F capacitor (C7) on the V
): Place a 0.1 F capacitor (C2) and a 10-47 F tantalum capacitor (C1) on the AV
DD
pin is connected to the same power supply as the V
CC
pin. An example of an LC filter [L
): Place one 0.1 F capacitor (C5) on the V
, should be connected to a low-noise power supply that has the same voltage as the digital
CC
): Place one 0.1 F capacitor (C3) on each V
CC
or V
CC
4
(Continued)
tantalum capacitor on the common net as close as possible to the chip.
), the ADC and DAC modules do not function correctly in such a case and may
BAT
input as required to meet UL regulations.
CC
) pin should be connected to the analog ground plane as close
DD
64
1
) pin should be located near the V
and (C
CC
) pin should be located near each V
1
BAT
+C
DD
CC
2
pin as close as possible to the pin.
)] is shown in Figure 11. An RC filter is obtained
-GND pin pair as close as possible to the pin
is internally isolated from V
CC
CC
IN
OUT
0-9 in Figure 11) should be connected to
-GND pin pair as close as possible to the
pin, it is recommended to use an external
IN
0-7 in Figure 11) should be connected
0-3 in Figure 11) should be connected
BAT
) pin should be located near the
DD
-GND pair; one side of
CC
CC
to enable AV
-GND pin pair;
CC
Revision 1.07
pin as
CC