MAX562 Просмотр технического описания (PDF) - Maxim Integrated
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MAX562 Datasheet PDF : 8 Pages
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Complete 230kbps, 2.7V to 5.25V
Serial Interface for Notebook Computers
+3V
SHDN
VOH
TRANSMITTER
OUTPUTS
VOL
A. TIMING DIAGRAM
0V
OUTPUT DISABLE TIME (tDT)
+3V
0V
-3V
1 OR 0
TX
B. TEST CIRCUIT
3k
50pF
Figure 3. Transmitter-Output Disable Timing
_______________Detailed Description
The MAX562 has three sections: the charge-pump voltage
converter, the drivers (transmitters), and the receivers.
Charge-Pump Voltage Converter
The charge-pump voltage converter is used to produce a
positive and a negative supply to drive the transmitters. The
positive voltage (V+) is generated by a regulated charge
pump working as either a doubler or a tripler (depending on
the VCC level) and using capacitors C1A, C1B and C3 (see
Typical Operating Circuit). The negative voltage (V-) derives
from V+ using a simple charge-pump inverter that employs
capacitors C2 and C4.
These charge-pump converters are regulated to give output
voltages of +5.8V and -5.2V. Having regulated supplies
generated on-chip makes the MAX562's performance insen-
sitive to variations in VCC from 2.7V to 5.25V, transmitter load-
ing changes, and operating temperature changes.
When SHDN is low, the charge pumps are disabled, V+ is
internally connected to VCC, and V- is internally connected to
GND.
EN
R_IN
A. TEST CIRCUIT
EN INPUT
R_OUT 1k
R_
VOH -1V,
VOL +1.6V
150pF
+3V
0V
EN
OUTPUT ENABLE TIME (tER)
VOH
RECEIVER
OUTPUTS
VOL
B. ENABLE TIMING
EN INPUT 0V
VOH
RECEIVER
OUTPUTS
VOL
C. DISABLE TIMING
+3V
EN
OUTPUT DISABLE TIME (tDR)
VOH -0.5V
VOL +0.5V
Figure 4. Receiver-Output Enable and Disable Timing
EIA/TIA-562 Drivers
The driver output voltage is guaranteed to meet the ±3.7V
EIA/TIA-562 specification over the full range of operating
temperatures and voltages, when each transmitter is
loaded with up to 3kΩ and operated up to 230kbps (see
Typical Operating Characteristics). The typical driver out-
put voltage swing exceeds ±4V with a 3kΩ load on all
transmitter outputs. The open-circuit output voltage swing
is typically from (V+ - 0.7V) to (V- + 0.7V). Output swing is
not significantly dependent on VCC since the charge
pumps are regulated.
Input thresholds are CMOS and TTL compatible. Connect
unused inputs to VCC or to GND.
When SHDN is low, the driver outputs are off and their leak-
age currents are less than 10µA, even if the transmitter
outputs are back-driven between -7V and +15V. Taking
SHDN low does not disable the receivers.
When SHDN and EN are both low, the entire chip is
disabled and all outputs are high impedance. Power
consumption is lowest in this condition. Exiting shutdown
takes about 100µs, but depends on VCC. Figure 5 shows
6 _______________________________________________________________________________________
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