AVCA (B) 164245 Translation Devices For LCD Module and Compact Flash Interfaces

LCD displays on mobile phones, digital cameras and PDA's are moving to higher-resolution color displays.

by Texas Instruments -- EDN, 5/18/2004

Technology Trend

LCD displays on mobile phones, digital cameras and PDA's are moving to higher-resolution color displays.
CPU and microcontroller I/O voltages are decreasing and moving to 2.5-V and below as core operating voltages migrate to 1.8-V and lower.
The existing controllers for LCD panels in the market still operate from 3 to 3.6-V supply voltages. Similarly, the LCD module interface in the market also remains fixed at the 3.3-V logic level.

Existing Problem

The I/O voltage mismatch between the processor and the LCD module makes it extremely difficult for these devices to interface and maintain acceptable noise margins.

Proposed Solution

The SN74AVCA164245 (or SN74AVCB164245) is a level-shifting logic buffer capable of translating from levels as low as 1.4-V up to a maximum of 3.6-V. It is ideally suited for interfacing with the lower-voltage microprocessor to the 3.3-V LCD module. Below is a block diagram showing the integration of the translation logic device onto the LCD module.

Compact Flash I/O Buffer

The compact flash (CF/CF+) standard provides interface to the CompactFlash (CF) flash data storage cards, magnetic disk cards and I/O cards including, but not limited to, serial cards, Ethernet cards, fax/modem cards, and wireless pager cards. A CompactFlash storage card also runs in True IDE Mode – making it electrically compatible with an IDE disk drive. The CF/CF+ connector consists of 50 pins with 11 address signals, 16 data signals, and other control signals.

Since most of the CF/CF+ cards in use today operate with a 3.3 V supply, and since the compact flash controller is embedded within the CPU and MCU, which is subject to the trend of decreasing I/O voltages (e.g., 1.8V), an external level shifter is required. The AVCA164245 or the AVCB164245 are ideal candidates for interfacing between these incompatible signal levels.

Input/Output Characteristics

The SN74AVCA164245 and SN74AVCB164245 translators are “split-rail” devices. One side is powered from VCC A while the opposite side is powered from VCC B. Logic I/O’s on the “A” side follow VCC A. Logic I/O’s on the “B” side follow VCC B. If VCC A and VCC B are powered from the same supply rail, then the device acts as a buffer with no translation. In total, 16 different level translation configurations can be achieved with a single device!

Features

Dynamic Drive Capability
- ± 24 mA at 3 V VCC
- ± 15 mA at 2.3 V VCC
- ± 9 mA at 1.65 V VCC
- ± 6 mA at 1.4 V VCC
Control Inputs (DIR, OE#) levels are referenced to VCC A (AVCA164245)
Control Inputs (DIR, OE#) levels are referenced to VCC B (AVCB164245)
Over-voltage tolerant up to 3.6 V
Ioff supports partial power down mode Target Applications
PDA, Smartphone
LCD Panel Module Interface
Digital Camera
Industrial Market

For More Information

Product Folder:
www.ti.com/sc/device/sn74avca164245
www.ti.com/sc/device/sn74avcb164245
Data Sheet:
www-s.ti.com/sc/techlit/sces395
www-s.ti.com/sc/techlit/sces394
Application Note:
www-s.ti.com/sc/techlit/scea030

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