DS2407 datasheet(31/31 Pages) DALLAS

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DS2407

012099 31/31

PIO SINK CURRENT

2.8V

VPUP

100 mA

90 mA

80 mA

70 mA

60 mA

50 mA

40 mA

30 mA

20 mA

10 mA

MAX.

MIN.

MAX.

MIN.

ISA, ISB

@ 0.4V

PIO–A

PIO–B

NOTES:

1. All voltages are referenced to ground.

2. VPUP, VPUPA, VPUPB = external pull–up voltage.

3. Input load is to ground.

4. An additional reset or communication sequence cannot begin until the reset high time has expired.

5. Read data setup time refers to the time the host must pull the 1–Wire bus low to read a bit. Data is guaranteed

to be valid within 1

µs of this falling edge and will remain valid for 14 µs minimum (15 µs total from falling edge

on 1–Wire bus).

6. VIH is a function of the chip–internal supply voltage. This voltage is determined by either the external pull–up resis-

tor and VPUP or the VCC supply, whichever is higher.

7. Capacitance on the data pin could be 800 pF when power is first applied. If a 5k

Ω resistor is used to pull up the

data line to VPUP, 5 µs after power has been applied the parasite capacitance will not affect normal communica-

tions.

8. tRSTL should be limited to maximum 5 ms. Otherwise the DS2407 may perform a power–on reset.

9. Input resistance is to ground.

10. VCC must be at least 4.0V if it is to be connected during a programming pulse.

11. If the current at PIO–A reaches 200 mA the gate voltage of the output transistor will be reduced to limit the sink

current to 200 mA. The user–supplied circuitry should limit the current flow through the PIO–transistor to no more

than 100 mA. Otherwise the DS2407 may be damaged.

12. PIO–A has a controlled turn–on output. The indicated currents are DC values. At VPUP = 4.0V or higher the sink

current typically reaches 80% of its DC value 1

µs after turning on the transistor.

13. Under certain low voltage conditions VILMAX may have to be reduced to as much as 0.5V to always guarantee

a presence pulse.

14. The input load current may be as high as 100

µA after a power–on reset until a memory function command byte

has been sent as well as during the execution of a ROM function command.

15. If the device is disconnected from the 1–Wire bus (data pin floating) channel A may lose its output status even

if VCC is connected. A resistor of approximately 100 kΩ between VCC and data will maintain the status of

channel A.

16. Without VCC supply, VIH for either PIO pin should always be greater than or equal to VPUP –0.3V.

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