DS485 datasheet(3/10 Pages) NSC

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Switching Characteristics

Over Supply Voltage and Operating Temperature Ranges, unless otherwise specified (Notes 3, 7, 8)

Symbol

Parameter

Conditions

Min

Typ

Max

Units

PLHD

Driver Differential Propagation Delay — Low to High

L = 54Ω,CL = 100 pF

PHLD

Driver Differential Propagation Delay — High to Low

SKEW

Differential Skew |t

PHLD −tPLHD|

Driver Rise Time

325

Driver Fall Time

325

Driver Enable to Output High

L = 100 pF

170

Driver Enable to Output Low

L = 100 pF

170

Driver Disable from Output Low

L = 15 pF

170

Driver Disable from Output High

L = 15 pF

170

PLHD

Receiver Differential Propagation Delay — Low to High

L = 15 pF (RO)

190

320

PHLD

Receiver Differential Propagation Delay — High to Low

210

320

SKEW

Differential Skew |t

PHLD −tPLHD|20

Receiver Enable to Output High

L = 15 pF

110

Receiver Enable to Output Low

110

Receiver Disable from Output Low

110

Receiver Disable from Output High

110

max

Maximum Data Rate

(Note 9)

2.5

Mbps

Note 1: “Absolute Maximum Ratings” are those values beyond which the safety of the device cannot be guaranteed. They are not meant to imply that the devices

should be operated at these limits. The table of “Electrical Characteristics” specifies conditions of device operation.

Note 2: Current into device pins is defined as positive. Current out of device pins is defined as negative. All voltages are referenced to ground except VOD1/2/3 and

VID.

Note 3: All typicals are given for: VCC = +5.0V, TA = +25˚C.

Note 4:

∆|VOD| and ∆|VOC| are changes in magnitude of V OD and VOCrespectively, that occur when the input changes state.

Note 5: IIN2 includes the receiver input current and driver TRI-STATE leakage current.

Note 6: Supply current specification is valid for loaded transmitters when DE = 0V or enabled (DE = H) with no load.

Note 7: f = 1 MHz, tr and tf ≤ 6 ns, ZO = 50Ω.

Note 8: CL includes jig and probe capacitance.

Note 9: fmax is the guaranteed data rate for 50 ft of twisted pair cable. f max may be conservatively determined from the ratio of driver transition time (tr) to the data

rate unit interval (1/fmax). Using a 10% ratio yields fmax = (0.1)/40 ns = 2.5 Mb/s. Higher data rates may be supported by allowing larger ratios.

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