FBL22040

Features:

• Resistor version of FB2040
• 8-bit BTL transceivers
• Separate I/O on TTL A-port
• Inverting
• Drives heavily loaded backplanes with equivalent load impedances down to 10W.
• High drive 100mA BTL open collector drivers on B-port
• Allows incident wave switching in heavily loaded backplane buses
• Reduced BTL voltage swing produces less noise and reduces power consumption
• Built-in precision band-gap reference provides accurate receiver thresholds and improved noise immunity
• Compatible with IEEE Futurebus+ or proprietary BTL backplanes
• Controlled output ramp and multiple GND pins minimize ground bounce
• Each BTL driver has a dedicated Bus GND for a signal return
• Glitch-free power up/power down operation
• Low ICC current
• Tight output skew
• Supports live insertion
• Pins for the optional JTAG boundary scan function are provided
• High density packaging in plastic Quad Flat Pack
• Same pin and function as FBL2040 except for a 30W series termination resistor
• The A outputs include a series resistor of 30W making external terminating resistors unnecessary


Pinout




Specifications

SYMBOL	PARAMETER		RATING	UNIT
VCC	Supply voltage		-0.5 to +4.6	V
VIN	Input voltage	AI0 AI7, OEB1, OEBn, OEA	-0.5 to +7.0	V
		B0 B7	-0.5 to +3.5
IIN	Input current		-18 to +5.0	mA
VOUT	Voltage applied to output in High output state		-0.5 to +7.0	V
LOUT	Current applied to output in Lowoutput state	A0 A7	24, 24	mA
		B0 B7	200
Tamb	Operating free-air temperature range		-40 to +85

Description

The FBL22040 is an 8-bit bidirectional BTL transceiver and is intended to provide the electrical interface to a high performance wired-OR bus. The FBL22040 is an inverting transceiver.

The FBL22040 B-port drivers are Low-capacitance open collectors with controlled ramp and are designed to sink 100mA. Precision band gap references on the B-port insure very good noise margins by limiting the switching threshold to a narrow region centered at 1.55V.

The FBL22040 B-port interfaces to "Backplane Transceiver Logic" (See the IEEE 1194.1 BTL standard). BTL features low power consumption by reducing voltage swing (1Vp-p, between 1V and 2V) and reduced capacitive loading by placing an internal series diode on the drivers. BTL also provides incident wave switching, a necessity for high performance backplanes.

The FBL22040 A-port operates at TTL levels with separate I/O. The 3-state A-port drivers are enabled when OEA goes High after an extra 6ns delay which is built in to provide a break-before-make function. When OEA goes Low, A-port drivers become High impedance without any extra delay. During power on/off cycles, the A-port drivers are held in a High impedance state when VCC is below 1.3V.

The FBL22040 B-port has two output enables, OEB0 and OEB1. When OEB0 is High and OEB1 is Low the output is enabled. When OEB0 is Low or if OEB1 is High, the B-port is inactive and is at the level of the backplane signal.

To support live insertion, FBL22040 OEB0 is held Low during power on/off cycles to insure glitch free B port drivers. Proper bias for B port drivers during live insertion is provided by the BIAS V pin when at a 3.3V level while V_CC is Low. If live insertion is not a requirement, the BIAS V pin should be tied to a V_CC pin.

The FBL22040 LOGIC GND and BUS GND pins are isolated in the package to minimize noise coupling between the BTL and TTL sides. These pins should be tied to a common ground external to the package.

Each FBL22040 BTL driver has an associated BUS GND pin that acts as a signal return path and these BUS GND pins are internally isolated from each other. In the event of a ground return fault, a "hard" signal failure occurs instead of a pattern dependent error that may be very infrequent and impossible to trouble-shoot.

The FBL22040 LOGIC V_CC and BUS V_CC pins are also isolated internally to minimize noise and may be externally decoupled separately or simply tied together.

FBL22040 JTAG boundary scan pins are provided with signals TMS, TCK, TDI and TDO. TMS and TCK are no-connects (no bond wires) and TDI and TDO are shorted together internally. Boundary scan functionality is not implemented at this time.