DS1482 Datasheet, PDF (1/7 Pages) Dallas Semiconductor – 1-Wire Level Shifter and Line Driver with Load Sensor

www.maxim-ic.com
FEATURES
§ Works with All iButtons^® and 1-Wire^®
Devices
§ Communicates at Regular and Overdrive 1-
Wire Speed (Host-Dependent)
§ Separate Interface Power Supply to Level
Shift to Non-5V Systems
§ External Strong-Pullup Control Pin can be
Used to Provide Low-On-Resistance-High
Current Power Source
§ Load Sensor to Detect when Strong-Pullup
Power Delivery is no Longer Needed
§ Power Delivery DONE Signal can be
Connected to Host Interrupt
§ Low-Cost 16-Pin SO Surface-Mount Package
§ Operating Temperature Range: -40°C to
+85°C
DS1482
1-Wire Level Shifter and Line Driver
with Load Sensor
PIN ASSIGNMENT
1 ^VCCQ
N.C. ₂
SPU 3
START 4
TXD ₅
N.C. ₆
GND ₇
N.C. 8
16 ^VCC
15 ^N.C.
14 PCTLZ
13 DONE
12 ^RXD
11 ^N.C.
10 ^I/O
9 N.C.
ORDERING INFORMATION
DS1482S
SO-16
DS1482S/T&R
SO-16, Tape-and-Reel
Contact the factory for versions with different
signal polarities.
DESCRIPTION
The DS1482 is a simple 1-Wire line driver with load sensor and level shifter, designed to function as an
interface between a 3V host system and a 1-Wire system that runs on 5V. Two supplies are provided, a
5V supply for the 1-Wire operations (V_CC) and an interface supply (V_CCQ). The DS1482 can connect
directly to a synchronous serial port if it supports the appropriate bit rates to generate 1-Wire timing.
Figure 1 shows the DS1482 block diagram. TXD is buffered and controls an N-channel transistor, which
drives the 1-Wire pin I/O low, e.g., to initiate a time slot. The logic level of the I/O pin is returned
through a level-shifting buffer to the RXD pin for the host processor to read. Figure 3 shows the
relationship of these signals in case of a 1-Wire read time slot.
The SPU input generates a control signal (PCTLZ) for an external low-impedance PMOS transistor
(Figure 2) that bypasses the 1-Wire pullup resistor (R_PUP) to provide power for 1-Wire devices with a
high-load current. PCTLZ is gated by the inverted TXD signal. This prevents a high through-current in
case TXD and SPU are high at the same time.
The DS1482 contains a high-precision comparator because it is important for the host micro to know
when the high load on the 1-Wire side is no longer active. As shown in Figure 4, the high current load
causes a small drop of the voltage on the I/O pin. The comparator detects when the high current phase
ends, and enables DONE after the deglitching time t_CF is over. The START signal allows the host micro
to selectively enable DONE.
iButton and 1-Wire are registered trademarks of Dallas Semiconductor.
1 of 7
032103