TLK4211EA Datasheet, PDF (2/17 Pages) Texas Instruments – 4.25 Gbps Cable and PC Board Equalizer

TLK4211EA
SLLS655 – NOVEMBER 2005
www.ti.com
BLOCK DIAGRAM
A simplified block diagram of the TLK4211EA is shown in Figure 1.
This compact, low-power 4.25-Gbps equalizer consists of a high-speed data path with offset cancellation
circuitry, a bandgap voltage reference, and bias current generation block.
The equalizer requires a single 3.3-V supply voltage. All circuit parts are described in detail in below.
COC2 COC1
Bandgap Voltage
Reference and
Bias Current
Generation
VCC
GND
Offset
Cancellation
OUTPOL
VCC
DIN+
DIN−
Fixed Equilizer
Stage
+
−
Gain Stage
+
−
Gain Stage
+
−
Gain Stage
+
−
CML
Output
Buffer
Stage
DOUT+
DOUT−
DISABLE
Figure 1. Simplified Block Diagram of the TLK4211EA
B0052-02
HIGH-SPEED DATA PATH
The high-speed data signal with frequency dependent loss is applied to the data path by means of the input
signal pins DIN+/DIN–. The data path consists of the fixed equalizer input stage with 100-Ω differential on-chip
line termination, three gain stages, which provide the required gain to ensure a limited output signal, and a CML
output stage. The equalized and amplified data output signal is available at the output pins DOUT+/DOUT–,
which provide 2 × 50-Ω back-termination to VCC. The output stage also includes a data polarity switching
function, which is controlled by the OUTPOL input, and a disable function controlled by the signal applied to the
DISABLE input pin.
An offset cancellation compensates inevitable internal offset voltages and thus ensures proper operation even for
small input data signals.
The low frequency cutoff is as low as 10 kHz with the built-in filter capacitor.
For applications which require even lower cutoff frequencies, an additional external filter capacitor may be
connected to the COC1/COC2 pins.
BANDGAP VOLTAGE AND BIAS GENERATION
The TLK4211EA equalizer is supplied by a single 3.3-V ±10% supply voltage connected to the VCC pins. This
voltage is referred to ground (GND).
An on-chip bandgap voltage circuitry generates a supply voltage independent reference from which all other
internally required voltages and bias currents are derived.
PACKAGE
The TLK4211EA is available in a small footprint 3 mm × 3 mm, 16-pin QFN package with a lead pitch of 0,5 mm.
The pin out is shown below in Figure 2.
2