The SZG-ADC-LTC226X is a 2-channel ADC based on the Analog Devices LTC226X ADCs. The converter module is perfect for high-performance communications applications and general high-speed data acquisition.

The module is configured to accept a conversion clock from the FPGA on the carrier or (with user-applied resistor changes) a single-ended clock delivered by an on-board SMA connector.



SYZYGY Information

Compatibility Table

Port typeSYZYGY Standard
5V supply requiredNo
Nominal 5V supply current0mA
Nominal 3.3V supply current500mA
VIO supply voltage1.2V to 3.3V
Nominal VIO supply current< 10mA
Total number of I/O15
Number of differential I/O pairs5

DNA Data

This data is stored in the SYZYGY DNA microcontroller on the SZG-ADC-LTC226X peripheral.

Max 5V Load0 mA
Max 3.3V Load500 mA
Max VIO Load10 mA
VIO Min1.2V
VIO Max3.3V


The source of the following pinout information is the SZG-ADC-LTC226X schematic. This pinout follows the SYZYGY specification for STD ports.

  • Column PIN NUM (J1) lists the pin number on the SYZYGY specification’s Standard Samtec connector, this is reference designator J1 in the schematic.
  • Column SIGNAL NAME lists the SYZYGY specification’s name for this pin’s connection.
  • Column SCHEMATIC NET lists the net name found in the SZG-ADC-LTC226X’s schematic for the connection.
6 D1PFR+
8 D1NFR-
11 D2NOUT1B-
10 D3POUT2A+
12 D3NOUT2A-
13 S8SDO
14 D5POUT2B+
16 D5NOUT2B-
15 S10CS_B
17 S12SCLK
19 S14SDI


The design of the SZG-ADC-LT226X has been heavily influenced by the evaluation board designed and produced by Linear Technology (Analog Devices).

Linear Technology (Analog Devices) LTC226X

From the LTC226X datasheet:

The LTC® 2268-14/LTC2267-14/LTC2266-14 and the LTC®2265-12/LTC2264-12/LTC2263-12 are 2-channel, simultaneous sampling A/D converters designed for digitizing high frequency, wide dynamic range signals. The former is a 14-bit converter with an AC performance of 73.1dB SNR and 88dB SFDR, while the latter is a 12-bit converter with an AC performance of 71dB SNR and 90dB SFDR. Both have ultralow jitter of 0.15psRMS, allowing undersampling of IF frequencies with excellent noise performance. The DC specs for the LTC® 2268-14/LTC2267-14/LTC2266-14 include ±1LSB INL (typ), ±0.3LSB DNL (typ), and no missing codes over temperature. The transition noise is a low 1.2LSB RMS. The DC specs for the LTC®2265-12/LTC2264-12/LTC2263-12 include ±0.3LSB INL (typ), ±0.1LSB DNL (typ), and no missing codes over temperature. The transition noise is a low 0.3LSB RMS

The digital outputs are serial LVDS to minimize the number of data lines. Each channel outputs two bits at a time (2-lane mode) or one bit at a time (1-lane mode). The LVDS drivers have optional internal termination and adjustable output levels to ensure clean signal integrity.

The ENC+ and ENC– inputs may be driven differentially or single-ended with a sine wave, PECL, LVDS, TTL, or CMOS inputs. An internal clock duty cycle stabilizer allows high performance at full speed for a wide range of clock duty cycles.

Analog Inputs

The applicable input frequency range of the SZG-ADC-LTC226X is approximately 5 MHz to 140 MHz. For optimal distortion and noise performance, or for input frequencies above 140 MHz, the RC networks on the analog inputs may need to be optimized. For optimal SNR performance, external filters may be required. Refer to the documentation below.

Maximum analog input voltage2 Vpp*
Input impedance 50 Ω

* The input range may be adjusted using the SENSE pin on the LTC226x. Refer to the documentation below.

Encode Clock Input

By default, the SZG-ADC is configured to accept a differential clock over the C2P_CLK connection from the carrier. To apply an external single-ended clock over the SMA connector J4, remove resistors R18 and R28, and place resistors R20 and R27.

The encode clock inputs may be driven at any level up to 3.6 V. When driving the inputs using a differential signal, the negative input (ENC-) must stay at least 200 mV above circuit ground.

Additional Documentation

Product Lifecycle

PCB Revision History

SZG-ADC-LTC226XDXXCurrent production PCB.

Known Issues


SDO Level Translator Incompatibility

The optional SDO connection in the SPI configuration interface is incompatible with the level translator. This means that the ADC’s configuration registers can be written to, but not read. Register read is only used to verify the written configuration, as there are no status or data registers available from that interface. A fix will be implemented in the next revision.