sx150x_89b-datasheet

ADVANCED COMMUNICATIONS & SENSING
Rev 4 – 26
th
April 2011 15 www.semtech.com
SX1508B/SX1509B
World’s Lowest Voltage Level Shifting GPIO
with LED Driver and Keypad Engine
• 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 SX1508B
and SX1509B 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
SX1508/9B
VCC2
IO4
1.2-3.6V
1.2-5.5V
1.2-3.6V
tLevelShiftMin
Figure 11 – Level Shifting Example
The minimum pulse width tLevelShiftMin which can be level shifted properly depends on VCCx and VDDM:
tLevelShiftMin = Input Delay + Core Delay + Output Delay
Input/Core/Output delays vs VCCx/VDDM are given in figures below.