DS1487 Datasheet, PDF (3/8 Pages) National Semiconductor (TI) – Low Power RS-485 1⁄4 Unit Load Multipoint Transceiver

Switching Characteristics
Over Supply Voltage and Operating Temperature Ranges, unless otherwise specified (Notes 4, 8, 9)
Symbol
t_PLHD
t_PHLD
t_SKEW
t_r
t_f
t_ZH
t_ZL
t_LZ
t_HZ
t_PLHD
t_PHLD
t_SKEW
t_ZH
t_ZL
t_LZ
t_HZ
f_max
Parameter
Driver Differential Propagation Delay — Low to High
Driver Differential Propagation Delay — High to Low
Differential Skew |t_PHLD − t_PLHD|
Driver Rise Time
Driver Fall Time
Driver Enable to Output High
Driver Enable to Output Low
Driver Disable from Output Low
Driver Disable from Output High
Receiver Differential Propagation Delay — Low to High
Receiver Differential Propagation Delay — High to Low
Differential Skew |t_PHLD − t_PLHD|
Receiver Enable to Output High
Receiver Enable to Output Low
Receiver Disable from Output Low
Receiver Disable from Output High
Maximum Data Rate
Conditions
Min Typ Max Units
R_L = 54Ω, C_L = 100 pF 10
40
80
ns
10 39 80
ns
0
1
10
ns
3
25 50
ns
3
25 50
ns
C_L = 100 pF
C_L = 100 pF
C_L = 15 pF
C_L = 15 pF
C_L = 15 pF (RO)
50 200
ns
65 200
ns
80 200
ns
80 200
ns
30 190 400
ns
30 210 400
ns
0
20 50
ns
C_L = 15 pF
45 150
ns
40 150
ns
50 150
ns
55 150
ns
(Note 10)
2.0
Mbps
Note 2: “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 3: Current into device pins is defined as positive. Current out of device pins is defined as negative. All voltages are referenced to ground except V_OD1/2/3and
V_ID.
Note 4: All typicals are given for: V_CC = +5.0V, T_A = +25˚C.
Note 5: ∆|V_OD| and ∆|V_OC| are changes in magnitude of V_OD and V_OC respectively, that occur when the input changes state.
Note 6: I_IN2 includes the receiver input current and driver TRI-STATE leakage current.
Note 7: Supply current specification is valid for loaded transmitters when DE = 0V or enabled (DE = H) with no load.
Note 8: f = 1 MHz, t_r and t_f ≤ 6 ns, Z_O = 50Ω.
Note 9: C_L includes jig and probe capacitance.
Note 10: f_max 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 (t_r) to the data
rate unit interval (1/f_max). Using a 10% ratio yields f_max = (0.1)/50 ns = 2.0 Mb/s. Higher data rates may be supported by allowing larger ratios.
Parameter Measurement Information
DS012920-2
FIGURE 1. V_OD
FIGURE 2. V_OD3
DS012920-3
3
FIGURE 3.
DS012920-4
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