Datasheet
Table Of Contents
- FEATURES
- APPLICATIONS
- DESCRIPTION
- ABSOLUTE MAXIMUM RATINGS
- ELECTRICAL CHARACTERISTICS
- DIGITAL CHARACTERISTICS
- FUNCTIONAL BLOCK DIAGRAM
- PIN CONFIGURATION
- TIMING CHARACTERISTICS
- LVDS OUTPUT TIMING CHARACTERISTICS
- LVDS OUTPUT TIMING CHARACTERISTICS
- TYPICAL CHARACTERISTICS
- SERIAL INTERFACE
- SERIAL REGISTER MAP
- SUMMARY OF FEATURES
- DESCRIPTION OF SERIAL REGISTERS
- THEORY OF OPERATION
- APPLICATION INFORMATION
- REVISION HISTORY

VREFT=1.5V+
V
CM
1.5V
VREFB=1.5V -
V
CM
1.5V
AFE5805
www.ti.com
SBOS421D –MARCH 2008–REVISED MARCH 2010
CLOCK, REFERENCE, AND DATA OUTPUT MODES
ADDRESS
IN HEX D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 NAME
1 1 X DIFF_CLK
1 1 X EN_DCC
42
1 1 X EXT_REF_VCM
1 1 X X PHASE_DDR<1:0>
1 1 X BTC_MODE
1 1 X MSB_FIRST
46
1 1 X EN_SDR
1 1 1 1 FALL_SDR
INPUT CLOCK
The AFE5805 is configured by default to operate with a single-ended input clock; CLKP is driven by a CMOS
clock and CLKM is tied to '0'. However, by programming DIFF_CLK to '1', the device can be made to work with a
differential input clock on CLKP and CLKM. Operating with a low-jitter differential clock generally leads to
improved SNR performance.
In cases where the duty cycle of the input clock falls outside the 45% to 55% range, it is recommended to enable
an internal duty cycle correction circuit. Enable this circuit by setting the EN_DCC bit to '1'.
EXTERNAL REFERENCE
The AFE5805 can be made to operate in external reference mode by pulling the INT/EXT pin to '0'. In this mode,
the REFT and REFB pins should be driven with voltage levels of 2.5V and 0.5V, respectively, and must have
enough drive strength to drive the switched capacitance loading of the reference voltages by each ADC. The
advantage of using the external reference mode is that multiple AFE5805 units can be made to operate with the
same external reference, thereby improving parameters such as gain matching across devices. However, in
applications that do not have an available high drive, differential external reference, the AFE5805 can still be
driven with a single external reference voltage on the CM pin. When EXT_REF_VCM is set as '1' (and the
INT/EXT pin is set to '0'), the CM pin is configured as an input pin, and the voltages on REFT and REFB are
generated as shown in Equation 1 and Equation 2.
(1)
(2)
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