AN2433 Freescale Semiconductor / Motorola, AN2433 Datasheet - Page 10

• Manufacturer Part Number: AN2433
• Description: 5V to 3V Design Considerations
• Manufacturer: Freescale Semiconductor / Motorola

AN2433/D
Microcontroller Outputs
Ports current drive
capabilities
10
over-voltages because this kind of device has a larger latch-up current rating
than most MCUs.
Figure 7. 5V CMOS or TTL output to 3.3V MCU input using an LCX device
The output structure of a digital circuit determines the output voltage swing and
the current capability. The MOS circuitry for an MCU pin capable of operating
as an output is shown in
To guarantee reliable output high voltage and low voltage the load current
should be limited within the specified values given on the data sheets.
If the pin current is increased to very high levels, which is typically over the
specified limit of 25 mA, the die substrate in the area around the protection
device will be influenced thus affecting the electrical characteristics of the
devices in the vicinity as well. This will cause physical damage to the pins.
Freescale Semiconductor, Inc.
For More Information On This Product,
5V System
5V System
5V to 3V Design Considerations
GND
GND
Go to: www.freescale.com
OUT
OUT
OUT
OUT
Figure 8
GND
GND
GND
GND
11
11
13
13
15
15
17
17
19
19
2
2
4
4
6
6
8
8
1
1
.
U1A
U1A
MC74LCX244
MC74LCX244
U1B
U1B
MC74LCX244
MC74LCX244
A0
A0
A1
A1
A2
A2
A3
A3
OE
OE
A0
A0
A1
A1
A2
A2
A3
A3
OE
OE
Y0
Y0
Y1
Y1
Y2
Y2
Y3
Y3
Y0
Y0
Y1
Y1
Y2
Y2
Y3
Y3
18
18
16
16
14
14
12
12
9
9
7
7
5
5
3
3
3.3V System
3.3V System
IN
IN
IN
IN
GND
GND
MOTOROLA