MB90820 Series
16
I
HANDLING DEVICES
1.
Preventing latch-up
CMOS ICs may cause latch-up in the following situations:
When a voltage higher than V
CC
or lower than V
SS
is applied to input or output pins.
When a voltage exceeding the rating is applied between V
CC
and V
SS
.
When the AV
CC
power supply is applied before the V
CC
voltage.
If latch-up occurs, the power supply current increases rapidly, sometimes resulting in thermal breakdown of the
device. Use meticulous care not to exceed the rating.
For the same reason, also be careful not to let the analog power-supply voltage exceed the digital power-supply
voltage.
Handling unused pins
2.
Unused input pins left open may cause abnormal operations, or latch-up leading to permanent damage. Unused
input pins should be pulled up or pulled down through at least 2 k
resistance.
Unused input/output pins may be left open in output state, but if such pins are in input state they should be
handled in the same way as input pins.
If any output pins are unused, set them to open.
Use of the external clock
3.
To use an external clock, drive only the X0 pin and leave the X1 pin open (See the illustration below).
4.
Power supply pins (V
CC
/V
SS
)
In products with multiple V
CC
or V
SS
pins, the pins of the same potential are internally connected in the device
to avoid abnormal operations including latch-up. However, you must connect the pins to external power supply
and a ground lines to lower the electro-magnetic emission level, to prevent abnormal operation of strobe signals
caused by the rise in the ground level, and to conform to the total output current rating.
Moreover, connect the current supply source with the V
CC
and V
SS
pins of this device at the low impedance.
It is also advisable to connect a ceramic bypass capacitor of approximately 0.1
μ
F between V
CC
and V
SS
near
this device.
Crystal oscillator circuit
5.
Noise near the X0 and X1 pins may cause the device to malfunction. Design the printed circuit board so that
X0, X1, the crystal oscillator (or ceramic oscillator) and the bypass capacitor to ground are located as close to
the device as possible.
It is strongly recommended to design the PC board artwork with the X0 and X1 pins surrounded by ground plane
because stable operation can be expected with such a layout.
Turning-on sequence of power supply to A/D converter and D/A converter
6.
Make sure to turn on the A/D converter and D/A converter power supply (AV
CC
, AV
SS
, AVR) and analog inputs
(AN0 to AN15) after turning-on the digital power supply (V
CC
).
MB90820 series
Open
X0
X1