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DS1482S
1-Wire Level Shifter and Line Driver with Load Sensor
DS1482
1-Wire Level Shifter and Line Driver
with Load Sensor
FEATURESWorks with All iButtons® and 1-Wire®
DevicesCommunicates at Regular and Overdrive 1-
Wire Speed (Host-Dependent)Separate Interface Power Supply to Level
Shift to Non-5V SystemsExternal Strong-Pullup Control Pin can be
Used to Provide Low-On-Resistance-High
Current Power SourceLoad Sensor to Detect when Strong-Pullup
Power Delivery is no Longer NeededPower Delivery DONE Signal can be
Connected to Host InterruptLow-Cost 16-Pin SO Surface-Mount PackageOperating Temperature Range: -40°C to
+85°C
PIN ASSIGNMENTVCCQ
N.C.
SPU
START
TXD
N.C.
GND
N.C.
VCC
N.C.
PCTLZ
DONE
RXD
N.C.
I/O
N.C.
ORDERING INFORMATIONDS1482SSO-16
DS1482S/T&RSO-16, Tape-and-ReelContact the factory for versions with different
signal polarities.
DESCRIPTIONThe 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, a5V supply for the 1-Wire operations (VCC) and an interface supply (VCCQ). 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 returnedthrough 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 (RPUP) to provide power for 1-Wire devices with ahigh-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when the high load on the 1-Wire side is no longer active.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 loadcauses 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 tCF is over. The START signal allows the host micro
DS1482
Figure 1. Block DiagramVCCQVCC
RXD
TXD
DONE
I/O
PCTLZSPU
LEVEL-SHIFT BOUNDARY
START
GND
DS1482
Figure 2. Typical Operating Circuit
Figure 3. DS1482 Application Signals, Normal Communication
Figure 4. DS1482 Application Signals, Strong Pullup Case
DS1482
Point 1:The 1-Wire slave device starts drawing current (internal micro or numeric processor is
running). The strong pullup (SPU) must be activated before the high current phase begins.
Point 2:The 1-Wire slave device no longer draws current. After the deglitching time (tCF) is over, the
DONE signal turns high. The START signal must be activated no later than tSD before tCF is
over. Typically START is activated shortly after SPU, but not before the 1-Wire slave devicehas started drawing high current.
Point 3:As soon as the DONE signal is high, the host micro ends the strong pullup by changing SPU
to low.
Point 4:While the DONE signal is high, the host micro changes START to low; this may occur
simultaneously with the state change of SPU or later. When START changes to low, DONEbecomes low.
Figure 5. Timing References TXD to I/O
Figure 6. Timing References I/O to RXD
DS1482
Figure 7. Timing References SPU to PCTLZ
Figure 8. Timing References START to DONE
DS1482
ABSOLUTE MAXIMUM RATINGS*Voltage to GND (All Pins)-0.5V, +6.0V
Combined Source/Sink Current (All Pins)20mA
Operating Temperature Range-40°C to +85°C
Junction Temperature+150°C
Storage Temperature Range-55°C to +125°CLead Temperature (Soldering)See IPC/JEDEC 020A
ESD requirements are 15kV for the I/O pin and 4kV for all other pins.This is a stress rating only and functional operation of the device at these or any other conditions
above those indicated in the operation sections of this specification is not implied. Exposure toabsolute maximum rating conditions for extended periods of time may affect reliability.
ELECTRICAL CHARACTERISTICS(VCC = 4.5V to 5.5V, VCCQ = 3.0V to 3.6V; TA = -40°C to +85°C.)
