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DS3884A
BTL Handshake Transceiver
General Description
The DS3884A is one in a series of transceivers designed
specifically for the implementation of high performance Futurebus+ and proprietary bus interfaces. The DS3884A is a
BTL 6-bit Handshake Transceiver designed to conform to
IEEE 1194.1 (Backplane Transceiver Logic—BTL) as specified in the IEEE 896.2 Futurebus+ specification.
Features
n Fast propagation delay (3 ns typ)
n 6-bit BTL transceiver
n Selective receiver glitch filtering (FR1–FR3)
n Meets 1194.1 Standard on Backplane Transceiver Logic
(BTL)
n Supports live insertion
n Glitch free power-up/down protection
n Typically less than 5 pF bus-port capacitance
n Low Bus-port voltage swing (typically 1V) at 80 mA
n TTL compatible driver and control inputs
n Separate TTL I/O
n Open collector bus-port outputs allow Wired-OR
connection
n Controlled rise and fall time to reduce noise coupling to
adjacent lines
n Built in Bandgap reference with separate QV
CC
and
QGND pins for precise receiver thresholds
n Exceeds 2 kV ESD testing (Human Body Model)
n Individual Bus-port ground pins
n Product offered in PQFP package styles
Connection Diagram
TRI-STATE®is a registered trademark of National Semiconductor Corporation.
DS011460-1
Order Number DS3884AVF
See NS Package VF44B
August 2000
DS3884A BTL Handshake Transceiver
© 2000 National Semiconductor Corporation DS011460 www.national.com
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Logic Diagram
DS011460-3
DS3884A
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Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage 6.5V
Control Input Voltage 6.5V
Driver Input and Receiver Output 5.5V
Receiver Input Current
±
15 mA
Bus Termination Voltage 2.4V
Power Dissipation at 25˚C
PQFP 1.3W
Derate PQFP Package 11.1 mW/˚C
Storage Temperature Range −65˚C to +150˚C
Lead Temperature
(Soldering, 4 seconds): 260˚C
Recommended Operating
Conditions
Supply Voltage, V
CC
4.5V–5.5V
Bus Termination Voltage (V
T
) 2.06V–2.14V
Operating Free Air Temperature 0˚C to 70˚C
DC Electrical Characteristics (Notes 2, 3)
TA= 0 to +70˚C, VCC=5V±10%
Symbol Parameter Conditions Min Typ Max Units
DRIVER AND CONTROL INPUT: (Dn, DE
*
, PS1 and PS2)
V
IH
Minimum Input High Voltage 2.0 V
V
IL
Maximum Input Low Voltage 0.8 V
I
I
Input Leakage Current VIN=VCC= 5.5V 100 µA
I
IH
Input High Current VIN= 2.4V 40 µA
I
IL
Input Low Current VIN= 0.5V −100 µA
V
CL
Input Diode Clamp Voltage I
CLAMP
= −12 mA −1.2 V
DRIVER OUTPUT/RECEIVER INPUT: (Bn)
V
OLB
Output Low Bus Voltage Dn = 2.4V, DE*= 0V, 0.75 1.0 1.1 V
(Note 5) I
OL
=80mA
I
OLBZ
Output Low Bus Current Dn = 0.5V, DE*= 2.4V, Bn = 0.75V 100 µA
I
OHBZ
Output High Bus Current Dn = 0.5V, DE*= 2.4V, Bn = 2.1V 100 µA
I
OLB
Output Low Bus Current Dn = 0.5V, DE*= 0V, Bn = 0.75V 220 µA
I
OHB
Output High Bus Current Dn = 0.5V, DE*= 0V, Bn = 2.1V 350 µA
V
TH
Receiver Input Threshold DE*= 2.4V 1.47 1.55 1.62 V
V
CLP
Positive Clamp Voltage VCC= Max or 0V, IBn= 1 mA 2.4 3.4 4.5 V
V
CC
= Max or 0V, IBn= 10 mA 2.9 3.9 5.0 V
V
CLN
Negative Clamp Voltage I
CLAMP
= −12 mA −1.2 V
RECEIVER OUTPUT: (FRn and Rn)
V
OH
Voltage Output High Bn = 1.1V, DE*= 2.4V, IOH= −2 mA 2.4 3.2 V
V
OL
Voltage Output Low Bn = 2.1V, DE*= 2.4V, IOL= 24 mA 0.35 0.5 V
Bn = 2.1V, DE
*
= 2.4V, IOL= 8 mA 0.35 0.4 V
I
OS
Output Short Circuit Current Bn = 1.1V, DE*= 2.4V (Note 4) −40 −70 −100 mA
SUPPLY CURRENT
I
CC
Supply Current: Includes VCC,DE
*
= 0.5V, All Dn = 2.4V 50 70 mA
QV
CC
and LI DE*= 2.4V, All Bn = 2.1V 50 70 mA
I
LI
Live Insertion Current DE*= 2.4V, All Dn = 0.5V 1 3 mA
DE
*
= 0.5V, All Dn = 2.4V 2 5 mA
Note 1: “Absolute Maximum Ratings” are those beyond which the safety of the device cannot be guaranteed. They are not meant to imply that the device should
be operated at these limits. The table of “Electrical Characteristics” provide conditions for actual device operation.
Note 2: All input and/or output pins shall not exceed V
CC
plus 0.5V and shall not exceed the absolute maximum rating at anytime, including power-up and
power-down. This prevents the ESD structure from being damaged due to excessive currents flowing from the input and/or output pins to QV
CC
and VCC. There is
a diode between each input and/or output to V
CC
which is forward biased when incorrect sequencing is applied. Alternatively, a current limiting resistor can be used
when pulling-up the inputs to prevent damage. The current into any input/output pin shall be no greater than 50 mA. Exception, LI and Bn pins do not have power
sequencing requirementswith respect to V
CC
and QVCC. Furthermore,the difference between VCCand QVCCshould neverbe greater than 0.5V atany time including
power-up.
Note 3: All currents intodevice pins are positive; all currents outof device pins are negative.All voltages are referenced to device groundunless otherwise specified.
All typical values are specified under these conditions.: V
CC
= 5V and TA= 25˚C unless otherwise stated.
Note 4: Only one output should be shorted at a time, and duration of the short should not exceed one second.
Note 5: Referenced to appropriate signal ground. Do not exceed maximum power dissipation of package.
DS3884A
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AC Electrical Characteristics (Note 6)
TA= 0˚C to +70˚C, VCC=5V±10%
Symbol Parameter Conditions Min Typ Max Units
DRIVER
t
PHL
Dn to Bn Prop. Delay DE*=0V 135 ns
t
PLH
(
Figure 1,Figure 2
) 135 ns
t
PHL
DE*to Bn Enable Time Dn = 3V 2 4 6 ns
t
PLH
Disable Time (
Figure 1,Figure 3
) 246 ns
t
r
Transition Time—Rise/Fall (
Figure 1,Figure 2
) 1 2 3.5 ns
t
f
20% to 80% 1 2 3.5 ns
SR Skew Rate is Calculated (Note 11) 0.5 V/ns
from 1.3V to 1.8V
t
skew
Skew between Drivers in (Note 7) 1 3 ns
the Same Package
RECEIVER
t
PHL
Bn to Rn Prop. Delay DE*=3V 245 ns
t
PLH
(
Figure 4,Figure 5
) 246 ns
t
skew
Skew between Receivers in (Note 7) 1 3 ns
Same Package
FILTERED RECEIVER
t
PHL
Bn to FRn Prop. Delay PS1 = 0V PS2 = 0V DE*= 3V 6 12 16 ns
(
Figure 4,Figure 5
), R
EXT
=13kΩ
PS1=0V PS2=3V DE
*
=3V 111621 ns
(
Figure 4,Figure 5
), R
EXT
=13kΩ
PS1=3V PS2=0V DE
*
=3V 152127 ns
(
Figure 4,Figure 5
), R
EXT
=13kΩ
PS1=3V PS2=3V DE
*
=3V 253345 ns
(
Figure 4,Figure 5
), R
EXT
=13kΩ
t
PLH
Bn to FRn Prop. Delay DE*=3V(
Figure 4,Figure 5
)
(Note 8)
257 ns
R
EXT
=13kΩ
t
GR
Glitch Rejection PS1 = 0V PS2 = 0V DE*=3V 5 9 16 ns
(
Figure 4,Figure 6
), R
EXT
=13kΩ
PS1=0V PS2=3V DE
*
=3V 101318 ns
(
Figure 4,Figure 6
), R
EXT
=13kΩ
PS1=3V PS2=0V DE
*
=3V 141824 ns
(
Figure 4,Figure 6
), R
EXT
=13kΩ
PS1=3V PS2=3V DE
*
=3V 243142 ns
(
Figure 4,Figure 6
), R
EXT
=13kΩ
FILTERED RECEIVER TIMING REQUIREMENTS
t
s
PSn to Bn Set-Up Time (
Figure 7
), R
EXT
=13kΩ 250 ns
PARAMETERS NOT TESTED
Coutput Capacitance at Bn (Note 9) 5 pF
t
NR
Noise Rejection (Note 10) 1 ns
Note 6: Input waveforms shall have a rise/fall time of 3 ns.
Note 7: t
skew
is an absolute value defined as differences seen in propagation delays between drivers in the same package with identical load conditions.
Note 8: Filtered receiver t
PLH
is independent of filter setting.
Note 9: The parameter is tested using TDR techniques described in P1194.0 BTL Backplane Design Guide.
Note 10: This parameter is tested during device characterization. The measurements revealed that the part will reject 1 ns pulse width.
Note 11: Futurebus+transceivers are required to limit bus signal rise and fall timesto no faster than 0.5V/ns, measured between 1.3V and 1.8V (approximately 20%
to 80% of nominal voltage swing). The rise and fall times are measured with a transceiver loading equivalent to 12.5Ω tied to +2.1V DC.
DS3884A
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Pin Descriptions
Pin Name Number of Input/ Description
Pins Output
B1–B6 6 I/O BTL receiver input and driver output
B1GND–B6GND 6 NA Driver output ground reduces bounce due to high
current switching of driver outputs
(Note 12)
DE
*
1 I Driver Enable Low
D1–D6 6 I TTL Driver Input
FR1–FR3 3 O TTL Filtered Receiver Output
GND 3 NA Ground reference for switching circuits.
(Note 12)
LI 1 NA Power supply for live insertion. Boards that require live
insertion should connect LI to the live insertion pin on
the connector. (Note 13)
NC 4 NA No Connect
PS1, PS2 2 I Pulse Width Selection pin determines glitch filter setting
(Note 14)
R1–R6 6 O TTL Receiver Output
REXT 1 NA External Resistor pin. External resistor is used for
internal biasing of filter circuitry. The 13 kΩ resistor shall
be connected between REXT and GND. The resistor
shall have a tolerance of 1% and a temperature
coefficient of 100 ppm/˚C or better.
QGND 2 NA Ground reference for receiver input bandgap reference
and non-switching circuits (Note 12)
QV
CC
1NAV
CC
supply for bandgap reference and non-switching
circuits (Note 13)
V
CC
2NAV
CC
supply for switching circuits (Note 13)
Note 12: the multiplicity of grounds reduces the effective inductance of bonding wires and leads, which then reduces the noise caused by transients on the ground
path. The various ground pins can be tied together provided that the external ground has low inductance (i.e., ground plane with power pins and many signal pins
connected to the backplane ground). If the external ground floats considerably during transients, precautionary steps should be takento prevent QGND from moving
with reference to the backplane ground. The receiver threshold should have the same ground reference as the signal coming from the backplane. A voltage offset
between their grounds will degrade the noise margin.
Note 13: The same considerations for ground are used for V
CC
in reducing lead inductance (see Note 12). QVCCand VCCshould be tied together externally.If live
insertion is not supported, the LI pin can be tied together with QV
CC
and VCC.
Note 14: See AC characteristics for filter setting.
DS3884A
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Pin Descriptions (Continued)
DE
*
Dn FRn Rn Bn
HXHHL
HXLLH
LHHHL
LLLLH
X: High or low logic state
L: Low state
H: High state
L-H: Low to high transition
Glitch Filter Table
PS1 PS2 Filter Setting
LL 5ns
L H 10 ns
H L 14 ns
H H 24 ns
Application Information
The DS3884A is pin to pin and functionally compatible with
the DS3884. The DS3884A is a speed and power enhanced
version of the DS3884. There are two minor differences between the DS3884 and DS3884A.
The external resistor used in the DS3884A is different from
that used in the DS3884. REXT for the DS3884 is 6.2k while
REXT for the DS3884A is 13k. The available filter settings for
the DS3884A are 5 ns, 10 ns, 14 ns, 24 ns, while the settings
for the DS3884 are 5 ns, 7.5 ns, 15 ns, and 25 ns.
Utilization of the DS3884A simplifies the implementation of
all handshake signals which require Wired-OR glitch filtering.
Three of the six bits have an additional parallel Wired-OR filtered receive output giving a total of nine receiver outputs.
DS011460-5
FIGURE 1. Driver Propagation Delay Set-Up
DS011460-6
FIGURE 2. Driver: Dn to Bn
DS011460-7
FIGURE 3. Driver: DE*to Bn
DS011460-8
Switch Position
t
PLH
t
PHL
S1 open close
FIGURE 4. Receiver Propagation Delay Set-Up
DS011460-9
FIGURE 5. Receiver: Bn to FRn, Bn to Rn
DS011460-10
FIGURE 6. Receiver: tGR, FRn(min) = 2V
DS011460-11
FIGURE 7. Receiver: PSn to Bn
DS3884A
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Application Information (Continued)
In Wired-OR applications, the glitch generated as drivers are
released from the bus, is dependent upon the backplane and
parasitic wiring components causing the characteristics of
the glitch to vary in pulse width and amplitude. Toaccommodate this variation the DS3884A features two pins defined as
PS1 and PS2 which allow selection of a 5 ns, 10 ns, 14 ns
and 24 ns filter setting to optimize glitch filtering for a given
situation. The REXT pin is issued in conjunction with the filtering circuitry and requires a 13 kΩ resistor to ground. For
additional information on Wired-OR glitch, reference Application Note AN-774.
The DS3884A driver output configuration is an NPN open
collector which allows Wired-OR connection on the bus.
Each driver output incorporates a Schottky diode in series
with its collector to isolate the transistor output capacitance
from the bus thus reducing the bus loading in the inactive
state. The combined output capacitance of the driver and receiver input is typically less than 5 pF. The driver also has
high sink current capability to comply with the bus loading requirements defined within IEEE 1194.1 BTL specification.
Backplane Transceiver Logic (BTL) is a signaling standard
that was invented and first introduced by National Semiconductor, then developed by the IEEE to enhance the performance of backplane buses. BTL compatible transceivers
feature low output capacitance drivers to minimize bus loading, a 1V nominal signal swing for reduced power consumption and receivers with precision thresholds for maximum
noise immunity. The BTL standard eliminates settling time
delays that severely limit TTL bus performance, and thus
provide significantly higher bus transfer rates. The backplane bus is intended to be operated with termination resistors (selected to match the bus impedance) connected to
2.1V at both ends. The low voltage is typically 1V.
Separate ground pins are provided for each BTL output to
minimize induced ground noise during simultaneous switching.
The device’s unique driver circuitry meets a maximum slew
rate of 0.5V/ns which allows controlled rise and fall times to
reduce noise coupling to adjacent lines.
The transceiver’s high impedance control and driver inputs
are fully TTL compatible.
The receiver is a high speed comparator that utilizes a bandgap reference for precision threshold control allowing maximum noise immunity to the BTL 1V signaling level.
Separate QV
CC
and QGND pins are provided to minimize
the effects of high current switching noise. Output pins
FR1–FR3 are the filtered outputs and R1–R6 are the unfiltered outputs. All receiver outputs are fully TTL compatible.
The DS3884A supports live insertion as defined for Futurebus+ through the LI (Live Insertion) pin. Toimplement live insertion the LI pin should be connected to the live insertion
power connector. If this function is not supported the LI pin
must be tied to the V
CC
pin. The DS3884A also provides
power up/down glitch free protection during power sequencing.
The DS3884A has two types of power connections in addition to the LI pin. They are the Logic V
CC(VCC
) and the Quiet
V
CC
(QVCC). There are two VCCpins on the DS3884A that
provide the supply voltage for the logic and control circuitry.
Multiple connections are provided to reduce the effects of
package inductance and thereby minimize switching noise.
As these pins are common to the V
CC
bus internal to the device, a voltage difference should never exist between these
pins and the voltage difference between V
CC
and QV
CC
should never exceed±0.5V because of ESD circuitry. Additionally,the ESD circuitry between the V
CC
pins and all other
pins except for BTL I/O’s and LI pins requires that any voltage on these pins should not exceed the voltage on V
CC
+
0.5V.
There are three different types of ground pins on the
DS3884A. They are the logic ground (GND), BTL grounds
(B1GND–B6GND) and the Bandgap reference ground
(QGND). All of these ground reference pins are isolated
within the chip to minimize the effects of high current switching transients. For optimum performance the QGND should
be returned to the connector through a quiet channel that
does not carry transient switching current. The GND and
B1GND–B6GND should be connected to the nearest backplane ground pin with the shortest possible path.
Since many different grounding schemes could be implemented and ESD circuitry exist on the DS3884A, it is important to note that any voltage difference between ground pins,
QGND, GND or B1GND–B6GND should not exceed
±
5V in-
cluding power up/down sequencing.
Additional transceivers included in the Futurebus+ / BTL
family are; the DS3883A BTL 9-bit Transceiver, and the
DS3886A BTL 9-bit Latching Data Transceiver featuring
edge triggered latches in the driver which may be bypassed
during a fall-through mode and a transparent latch in the receiver.
DS3884A
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Physical Dimensions inches (millimeters) unless otherwise noted
LIFE SUPPORT POLICY
NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT
DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL
COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:
1. Life support devices or systems are devices or
systems which, (a) are intended for surgical implant
into the body, or (b) support or sustain life, and
whose failure to perform when properly used in
accordance with instructions for use provided in the
labeling, can be reasonably expected to result in a
significant injury to the user.
2. A critical component is any component of a life
support device or system whose failure to perform
can be reasonably expected to cause the failure of
the life support device or system, or to affect its
safety or effectiveness.
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www.national.com
44-Pin PQFP
Order Number DS3884AVF
NS Package VF44B
DS3884A BTL Handshake Transceiver
National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.
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