Datasheet

5
LT1785/LT1785A
LT1791/LT1791A
TYPICAL PERFORMANCE CHARACTERISTICS
UW
Supply Current vs Temperature
Driver Propagation Delay
vs Temperature
LT1791 Driver Output Leakage
DE = 0V
TEMPERATURE (°C)
–40
PROPAGATION DELAY (ns)
1000
900
800
700
600
500
400
300
200
100
0
0
40
60
1785/91 G04
–20
20
80
100
HL
LH
1mA/DIV
–60V 60V
LT1791 Receiver Input Current
vs V
IN
200µA/DIV
–60V 60V
V
IN
1785/91 G06
–60V 60V
1mA/DIV
V
A,
V
B
1785/91 G07
V
OUT
1785/91 G05
TEMPERATURE (°C)
–40
I
CC
(mA)
7
6
5
4
3
2
1
0
0
40
60
1785/91 G08
–20
20
80
100
RECEIVER ONLY
STANDBY
DRIVER AND
RECEIVER ON
Receiver Propagation Delay
vs Differential Input Voltage
LT1785 Input Characteristics
Pins A or B; DE = RE = 0V
V
IN
DIFFERENTIAL (V)
0
DELAY (ns)
700
600
500
400
300
200
100
0
1785/91 G09
2
5
1
34
HL V
CM
= 12V
HL V
CM
= –7V
LH V
CM
= –7V
LH V
CM
= 12V
PIN FUNCTIONS
UUU
RO: Receiver Output. TTL level logic output. If the receiver
is active (RE pin low), RO is high if receiver input A ≥ B by
200mV. If A ≤ B by 200mV, then RO will be low. RO
assumes a high impedance output state when RE is high
or the part is powered off. RO is protected from output
shorts from ground to 6V.
RE: Receiver Output Enable. TTL level logic input. A logic
low on RE enables normal operation of the receiver output
RO. A logic high level at RE places the receiver output pin
RO into a high impedance state. If receiver enable RE and
driver enable DE are both in the disable state, the circuit
goes to a low power shutdown state. Placing either RE or
DE into its active state brings the circuit out of shutdown.
Shutdown state is not entered until a 3µs delay after both
RE and DE are disabled, allowing for logic skews in
toggling between transmit and receive modes of opera-
tion. For CAN bus applications, RE should be tied low to
prevent the circuit from entering shutdown.
DE: Driver Output Enable. TTL level logic input. A logic
high on DE enables normal operation of the driver outputs
(Y and Z on LT1791, A and B on LT1785). A logic low level
at DE places the driver output pins into a high impedance