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SX1512BIULTRT Datasheet(PDF) 15 Page - Semtech Corporation

Part No. SX1512BIULTRT
Description  World’s Lowest Voltage Level Shifting GPIO with LED Driver and Keypad Engine
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Maker  SEMTECH [Semtech Corporation]
Homepage  http://www.semtech.com
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SX1512BIULTRT Datasheet(HTML) 15 Page - Semtech Corporation

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ADVANCED COMMUNICATIONS & SENSING
Rev 4 – 26
th April 2011
15
www.semtech.com
SX1511B/SX1512B
World’s Lowest Voltage Level Shifting GPIO
with LED Driver and Keypad Engine
IO3
IO2
IO1
IO0
IO4
IO5
IO6
IO7
SX1511B
- IO[3-0] as outputs (scanning)
- IO[7-4] as inputs
X
Y
RegKeyData =
X
Y
Figure 9 – 4x4 Keypad Connection to SX1511B
Following procedure should be implemented on the host controller for a 4x4 keypad:
1. Set RegDir to 0xF0 (IO[3-0] as outputs, IO[7-4] as inputs) , set RegOpenDrain to 0x0F (IO[3-0] as open-drain
outputs), set RegPullup to 0xF0 (pull-ups enabled on inputs IO[7-4]).
2. Enable and configure debouncing on IO[7-4] (RegDebounceEnable = 0xF0, Ex : RegDebounceConfig = 0x05)
3. Enable and configure keypad scanning engine (Ex : RegKeyConfig = 0x7D) This will start an infinite loop with
the following sequence to IO[3:0]: ZZZ0, ZZ0Z, Z0ZZ, 0ZZZ. Make sure that scan interval is set to higher value
than the debounce time.
4. When a key is pressed, NINT goes low, key scan is halted and the key coordinates are stored in RegKeyData:
The column data will be stored in RegKeyData[7:4] (Note: column indication is active low)
The row data will be stored in RegKeyData[3:0] (Note: row indication is active low)
When RegKeyData is read, this data along with the interrupt is automatically cleared (same behavior
as reading RegData) and the key scan continues to the next row.
5. Restart from point 4.
This implementation allows the host to handle both single and multi-touches easily (fast AAAAAA sequence is a
long press of key A, fast ABABABAB sequence is key A and key B pressed together, etc)
4.5.3
Level Shifter
Because of their 5.5V tolerant I/O banks with independent supply voltages between 1.2V and 3.6V, the SX1511B
and SX1512B can perform level shifting of signals from one I/O bank to another without uC activity by
programming the corresponding configuration register bits accordingly in RegLevelShifter (and RegDir).
This can save significant BOM cost in a final application where only a few signals need to be level-shifted (no
need for an additional external level shifter IC).
VCC1
IO0
1.2-3.6V
SX1510/11B
VCC2
IO4
1.2-3.6V
1.2-5.5V
1.2-3.6V
Figure 10 – Level Shifting Example


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