ADUC847BCP8-5 AD [Analog Devices], ADUC847BCP8-5 Datasheet - Page 88

• Manufacturer Part Number: ADUC847BCP8-5
• Description: MicroConverter Multichannel 24-/16-Bit ADCs with Embedded 62 kB Flash and Single-Cycle MCU
• Manufacturer: AD [Analog Devices]

ADuC845/ADuC847/ADuC848
As an alternative to providing two separate power supplies,
AV
ferrite bead between it and DV
separately to ground. An example of this configuration is shown
in Figure 65. In this configuration, other analog circuitry (such
as op amps and voltage reference) can be powered from the
AV
Notice that in both Figure 64 and Figure 65 a large value (10 µF)
reservoir capacitor sits on DV
sits on AV
located at each V
practice, be sure to include all of these capacitors and ensure
that the smaller capacitors are closer than the 10 µF capacitors
to each V
the ground terminal of each of these capacitors directly to the
underlying ground plane. Finally, note that, at all times, the
analog and digital ground pins on the part must be referenced
to the same system ground reference point. It is recommended
that the CSP paddle be soldered to ensure mechanical stability
but be floated with respect to system V
POWER-ON RESET OPERATION
An internal power-on reset (POR) is implemented on the
ADuC845/ADuC847/ADuC848. For DV
internal POR holds the part in reset. As DV
an internal timer times out for typically 128 ms before the part
is released from reset. The user must ensure that the power
supply has at least reached a stable 2.7 V minimum level by this
time. Likewise on power-down, the internal POR holds the part
in reset until the power supply drops below 1 V. Figure 66
illustrates the operation of the internal POR.
Figure 66. ADuC845/ADuC847/ADuC848 Internal Power-On Reset Operation
Figure 65. External Single-Supply Connections (56-Lead CSP Pin Numbering)
DV
CORE RESET
INTERNAL
DD
DD
DD
can be kept quiet by placing a small series resistor and/or
supply line as well.
2.63V TYP
1.0V TYP
DIGITAL SUPPLY
DD
DD
+
–
pin with lead lengths as short as possible. Connect
0.1 µ F
. Also, local decoupling capacitors (0.1 µF) are
DD
pin of the chip. As per standard design
128ms TYP
10 µ F
22
36
51
23
37
38
50
DV
DGND
DD
BEAD
DD
DD
ADuC845/
ADuC847/
ADuC848
and a separate 10 µF capacitor
, and then decoupling AV
128ms TYP
1.6 Ω
DD
AGND
AV
s or grounds.
DD
DD
DD
below 2.63 V, the
4
5
6
rises above 2.63 V,
10 µ F
0.1 µ F
1.0V TYP
DD
Rev. A | Page 88 of 108
POWER CONSUMPTION
The DV
normal and power-down modes. The AV
current is specified with the analog peripherals disabled. The
normal mode power consumption represents the current drawn
from DV
(such as the watchdog timer and power supply monitor)
consume negligible current and are therefore included with the
normal operating current. The user must add any currents
sourced by the parallel and serial I/O pins, and those sourced by
the DAC to determine the total current needed at the ADuC845/
ADuC847/ADuC848 DV
drawn from the DV
during Flash/EE erase and program cycles.
POWER-SAVING MODES
Setting the power-down mode bit, PCON.1, in the PCON SFR
described in Table 6, allows the chip to be switched from
normal mode into full power-down mode.
In power-down mode, both the PLL and the clock to the core
are stopped. The on-chip oscillator can be halted or can
continue to oscillate, depending on the state of the oscillator
power-down bit (OSC_PD) in the PLLCON SFR. The TIC,
driven directly from the oscillator, can also be enabled during
power-down. However, all other on-chip peripherals are shut
down. Port pins retain their logic levels in this mode, but the
DAC output goes to a high impedance state (three-state) while
ALE and PSEN outputs are held low. There are five ways to
terminate power-down mode:
•
•
•
Asserting the RESET Pin
Returns to normal mode. All registers are set to their reset
default value and program execution starts at the reset
vector once the RESET pin is de-asserted.
Cycling Power
All registers are set to their default state and program exe-
cution starts at the reset vector approximately 128 ms later.
Time Interval Counter (TIC) Interrupt
If the OSC_PD bit in the PLLCON SFR is clear, the 32 kHz
oscillator remains powered up even in power-down mode.
If the time interval counter (wake-up/RTC timer) is
enabled, a TIC interrupt wakes the part from power-down
mode. The CPU services the TIC interrupt. The RETI at
the end of the TIC ISR returns the core to the next
instruction after that one that enabled power-down.
DD
DD
power supply current consumption is specified in
by the digital core. The other on-chip peripherals
DD
supply increases by approximately 5 mA
DD
and AV
DD
supply pins. Also, current
DD
power supply