sx150x_89b-datasheet

ADVANCED COMMUNICATIONS & SENSING
Rev 4 – 26
th
April 2011 12 www.semtech.com
SX1508B/SX1509B
World’s Lowest Voltage Level Shifting GPIO
with LED Driver and Keypad Engine
4.3 Reset
4.3.1 Hardware (NRESET)
The SX1508B and SX1509B generate their own power on reset signal after a power supply is connected to the
VDDM pin. NRESET input pin can be used to reset the chip anytime, it must be connected to VDDM (or greater)
either directly (if not used), or via a resistor.
Undefined
t
RESET
Reset
Signal
VDDM
VPOR
t
PULSE
VDROPH
Undefined
t
RESET
Undefined
1
2
3
4
5
6
2
1
VDROPL
Figure 6 – Power-On / Brown-out Reset Conditions
1. Device behavior is undefined until VDDM rises above VPOR, at which point internal reset procedure is
started.
2. After t
RESET
, the reset procedure is completed.
3. In operation, the SX1508B and SX1509B may be reset (POR like or LED driver counters only depending
on RegMisc setting) at anytime by an external device driving NRESET low for t
PULSE
or longer. Chip can
be accessed normally again after NRESET rising edge.
4. During a brown-out event, if VDDM drops above VDROPH a reset will not occur.
5. During a brown-out event, if VDDM drops between VDROPH and VDROPL a reset may occur.
6. During a brown-out event, if VDDM drops below VDROPL a reset will occur next time VPOR is crossed.
Please note that a brown-out event is defined as a transient event on VDDM. If VDDM is attached to a battery,
then the gradual decay of the battery voltage will not be interpreted as a brown-out event.
Please also note that a sharp rise in VDDM (> 1V/us) may induce a circuit reset.
4.3.2 Software (RegReset)
Writing consecutively 0x12 and 0x34 to RegReset register will reset all registers to their default values.
4.4 2-Wire Interface (I
2
C)
The SX1508B and SX1509B 2-wire interface operates only in slave mode. In this configuration, the device has
one or 4 possible devices addresses defined by ADDR[1:0] pins:
Device ADDR[1:0] Address Description
00 0x20 (0100000)
First address of the 2-wire interface
01 0x21 (0100001)
Second address of the 2-wire interface
10 0x22 (0100010)
Third address of the 2-wire interface
SX1508B
11 0x23 (0100011)
Fourth address of the 2-wire interface
00 0x3E (0111110)
First address of the 2-wire interface
01 0x3F (0111111)
Second address of the 2-wire interface
10 0x70 (1110000)
Third address of the 2-wire interface
SX1509B
11 0x71 (1110001)
Fourth address of the 2-wire interface
Table 6 - 2-Wire Interface Address
2 lines are used to exchange data between an external master host and the slave device:
• SCL : Serial CLock
• SDA : Serial DAta