CBM3485
DATASHEET
FEATURES
Low Quiescent Current: 300µA
-7V to +12V Common-Mode Input Voltage Range
Three-State Outputs
80ns Propagation Delays, 5ns Skew
Half-Duplex Versions Available
Operate from a Single 3.3V Supply
Allows up to 32 Transceivers on the Bus
Data rate: 10 Mbps
Current-Limiting and Thermal Shutdown for Driver Overload Protection
Enhanced ESD Specifications:
±15kV IEC61000-4-2 Air Discharge
±8kV IEC61000-4-2 Contact Discharge
GENERAL DESCRIPTION
The CBM3485is low-power transceivers for RS-485 and RS- 422 communication. IC contains
one driver and one receiver. The driver slew rates of the CBM3485 is not limited, allowing them
to transmit up to 10Mbps.
These transceivers draw between 120µA and 500µA of supply current when unloaded or fully
loaded with disabled drivers. All parts operate from a single 3.3V supply. Drivers are short-circuit
current limited and are protected against excessive power dissipation by thermal shutdown
circuitry that places the driver outputs into a high-impedance state. The receiver input has a failsafe feature that guarantees a logic-high output if the input is open circuit.
1
www.corebai.com
CBM3485
DATASHEET
Pin Description
Figure 2
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (VCC) 7V
Continuous Power Dissipation (TA= +70℃)
Control Input Voltage -0.3V to 7V
8-Pin Plastic DIP (derate 9.09mW/℃ above+70℃) 727mW
Driver Input Voltage (DI) -0.3V to 7V
8-Pin SOP (derate 5.88mW/℃ above +70℃) 471mW
Driver Output Voltage (A, B) -7.5V to +12.5V
Operating Temperature Ranges -40℃ to +125℃
Receiver Input Voltage (A, B) -7.5V to +12.5V
Storage Temperature Range -65°C to +160℃
Receiver Output Voltage (RO) -0.3V to
Lead Temperature (soldering, 10sec) +300℃
(VCC+0.3V)
* Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device.
These are stress ratings only and functional operation of the device at these or any other conditions beyond
those indicated under “recommended operating conditions” is not implied.
Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
2
www.corebai.com
CBM3485
DATASHEET
Electrical Parameters
(VCC = 3.3V ±0.3V, TA = TMIN to TMAX, unless otherwise noted.) (Notes 1, 2)
PARAMETER
Differential Driver Output (no load)
Differential Driver Output (with
load)
SYMBOL
CONDITIONS
MIN
TYP
VOD1
VOD2
R = 100Ω (RS-422)
R=54Ω (RS-485), Figure 4
MAX
UNITS
3
V
1
V
0.8
Change in Magnitude of Driver
Differential Output Voltage for
∆VOD
R = 54Ω or 50Ω, Figure 4
0.2
V
VOC
R = 54Ω or 100Ω, Figure 4
2
V
∆VOC
R = 54Ω or 100Ω, Figure 4
0.2
V
Complementary Output States
Driver Common-Mode Output
Voltage
Change in Magnitude of Driver
Common-Mode Output Voltage for
Complementary Output States
Input High Voltage
VIH
DE, DI, RE
Input Low Voltage
VIL
DE, DI, RE
0.8
V
Input Current
IIN1
DE, DI, RE
±2
μA
Input Current (A, B)
IIN2
Receiver Differential Threshold
Voltage
VTH
2.0
V
DE = 0V;
VIN=12V
1.0
VCC=0Vor 3.35V
VIN=-7V
-0.8
-7V ≤ VCM ≤12V
-0.2
0.2
V
Receiver Input Hysteresis
∆VTH
VCM = 0V
Receiver Output High Voltage
VOH
IO = -1.5mA, VID = 200mV
Receiver Output Low Voltage
VOL
IO = 2.5mA, VID = -200mV
0.4
V
IOZR
0.4V ≤ VO ≤ 2.4V
±1
µA
RIN
-7V ≤ VCM ≤ 12V
Three-State (high impedance)
Output Current at Receiver
Receiver Input Resistance
No-Load Supply Current (Note 3)
ICC
70
mA
mV
2.5
V
12
kΩ
DE = VCC
500
800
RE = 0V or VCC
300
400
DE = 0V
Driver Short-Circuit Current,
VO = High
Driver Short-Circuit Current
VO = Low
Receiver Short-Circuit Current
ESD Protection
μA
IOSD1
-7V≤VO≤12V (Note 4)
250
mA
IOSD2
-7V≤VO≤12V (Note 4)
250
mA
IOSR
0V ≤ VO ≤ VCC
95
mA
A, B, Y and Z pins, tested
using Human Body Model
±6.5
±15
3
www.corebai.com
kV
CBM3485
DATASHEET
SWITCHING CHARACTERISTICS
(VCC = 3.3V ±0.3V, TA = TMIN to TMAX, unless otherwise noted.) (Notes 1, 2)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
tPLH
RDIFF = 54Ω
10
80
100
tPHL
CL1 = CL2 = 100pF
10
80
100
Driver Output Skew to Output
tSKEW
RDIFF = 54,CL1=CL2= 100pF
5
10
ns
Driver Enable to Output High
tZH
CL= 100pF, S2 closed
55
80
ns
Driver Enable to Output Low
tZL
CL= 100pF, S1 closed
55
80
ns
Driver Disable Time from Low
tLZ
CL= 15pF, S1 closed
60
90
ns
Driver Disable Time from High
tHZ
CL= 15pF, S2 closed
60
90
ns
| tPLH - tPHL | Differential
tSKD
RDIFF = 54Ω
13
20
ns
tPLH
RDIFF = 54Ω
20
120
200
tPHL
CL1 = CL2 = 100pF
20
120
200
CL1 = CL2 = 100pF
5
10
Driver Input to Output
Receiver Input to Output
Receiver Skew | tPLH - tPHL |
ns
ns
Receiver Enable to Output Low
tZL
CRL = 15pF, S1 closed
50
90
ns
Receiver Enable to Output High
tZH
CRL = 15pF, S2 closed
50
90
ns
Receiver Disable Time from Low
tLZ
CRL = 15pF, S1 closed
40
80
ns
Receiver Disable Time from High
tHZ
CRL = 15pF, S2 closed
40
80
ns
Maximum Data Rate
fMAX
10
Mbps
Note 1: All currents into device pins are positive; all currents out of device pins are negative. All voltages are
referenced to device ground unless otherwise specified.
Note 2: All typical specifications are given for VCC=3.3V and TA=+25℃.
Note 3: Supply current specification is valid for loaded transmitters when DE=0V.
Note 4: Applies to peak current.
4
www.corebai.com
CBM3485
DATASHEET
TEST CIRCUITS
Figure 1. Driver VOD and VOC
Figure 2. Driver VOD with Varying Common-Mode
Voltage
Figure 3. Receiver VOH and VOL
Figure 4. Driver Differential Output Delay and Transition Times
5
www.corebai.com
CBM3485
DATASHEET
Figure 5. Driver Propagation Times
Figure 6. Driver Enable and Disable Times (tPZH, tPSH, tPHZ)
Figure 7. Driver Enable and Disable Times (tPZL, tPSL, tPLZ)
6
www.corebai.com
CBM3485
DATASHEET
Figure 8. Receiver Propagation Delay
Figure 9. Receiver Enable and Disable Times
Note 5: The input pulse is supplied by a generator with the following characteristics: PRR = 250kHz, 50%
duty cycle, tr≤6.0ns, ZO = 50Ω.
Note 6: CL includes probe and stray capacitance.
7
www.corebai.com
CBM3485
DATASHEET
Function Tables
Transmitting
INPUTS
Receiving
OUTPUTS X
INPUTS
OUTPUTS
RE
DE
DI
Z
Y
RE
DE
A-B
RO
X
1
1
0
1
0
0
+0.2V
1
X
1
0
1
0
0
0
-0.2V
0
0
0
X
Z
Z
0
0
open
1
1
0
X
Z
Z
1
0
X
Z
X-don’t care
Z-high impedance
Typical Information
Figure 10. CBM3485 Typical RS-485 Network
8
www.corebai.com
CBM3485
DATASHEET
Driver Output Protection
Excessive output current and power dissipation caused by faults or by bus contention are
prevented by two mechanisms. A foldback current limit on the output stage provides immediate
protection against short circuits over the whole common-mode voltage range. In addition, a
thermal shutdown circuit forces the driver outputs into a high-impedance state if the die
temperature rises excessively.
Propagation Delay
Skew time is simply the difference between the low-to-high and high-to-low propagation
delay. Small driver/receiver skew times help maintain a symmetrical mark-space ratio (50% duty
cycle).
The receiver skew time, |tPRLH - tPRHL|, is under 10ns. The driver skew times are 5ns for
the CBM3485.
Typical Applications
CBM3485 transceivers are designed for bidirectional data communications on multipoint
bus transmission lines. Figure 10 shows typical network applications circuits. These parts can
also be used as line repeaters, with cable lengths longer than 4000 feet.
To minimize reflections, the line should be terminated at both ends in its characteristic
impedance, and stub lengths off the main line should be kept as short as possible.
9
www.corebai.com
CBM3485
DATASHEET
PACKAGE
NOTES: 1. Dimensions “A”, “B” do not include mold flash or protrusions.
Maximum mold flash or protrusions 0.25 mm (0.010) per side.
Symbol
Dimensions ,mm
Min
Max
A
8.51
10.16
B
6.1
7.11
C
5.33
D
0.36
0.56
F
1.14
1.78
G
2.54
H
7.62
J
0°
10°
K
2.92
3.81
L
7.62
8.26
M
0.2
0.36
N
0.38
10
www.corebai.com
CBM3485
DATASHEET
NOTES: 1. Dimensions A and B do not include mold flash or protrusion.
2.
Maximum mold flash or protrusion 0.15 mm (0.006) per side for A; for B ‑
0.25 mm (0.010) per side.
Symbol
Dimensions ,mm
Min
Max
A
4.8
5
B
3.8
4
C
1.35
1.75
D
0.33
0.51
F
0.4
1.27
G
1.27
H
5.72
J
0°
8°
K
0.1
0.25
M
0.19
0.25
P
5.8
6.2
R
0.25
0.5
11
www.corebai.com
CBM3485
DATASHEET
PACKAGE/ORDERING INFORMATION
PRODUCT
ORDERING
PAKEAGE
TRANSPOT
MARKING
MEDIA,QUANTILY
SOIC-8(SOP8)
CBM3485A
Tape and Reel,2500
SOIC-8(SOP8)
CBM3485AC
Tape and Reel,2500
TEMPRANGE
PACKAGE
CBM3485AS
-40℃~125℃
CBM3485ACS
-0℃~70℃
NUMBER
CBM3485
12
www.corebai.com