Quad sine-wave clock buffer with LDO

The CDC3S04 is a four-channel low-power low-jitter sine-wave clock buffer. It can be used to buffer a single master clock to multiple peripherals. The four sine-wave outputs (CLK1–CLK4) are designed for minimal channel-to-channel skew and ultralow additive output jitter.

Each output has its own clock request inputs which enables the dedicated clock output. These clock requests are active-high (can also be changed to be active-low via I2C), and an output signal is generated that can be sent back to the master clock to request the clock (MCLKREQ). MCKLREQ is an open-source output and supports the wired-OR function (default mode). It needs an external pulldown resistor. MCKLREQ can be changed to wired-AND or push-pull functionality via I2C.

The CDC3S04 also provides an I2C interface (Hs-mode) that can be used to enable or disable the outputs, select the polarity of the REQ inputs, and allow control of internal decoding.

The CDC3S04 features an on-chip high-performance LDO that accepts voltages from 2.3 V to 5.5 V and outputs a 1.8-V supply. This 1.8-V supply can be used to power an external 1.8-V TCXO. It can be enabled or disabled for power saving at the TCXO.

A low signal at the RESET input switches the outputs CLK1 and CLK4 into the default state. In this configuration, CLK1 and CLK4 are ON (see ); the remaining device function is not affected. Also, the RESET input provides a glitch filter which rejects spikes of typical 300 ns on the RESET line to preserve false reset. A complete device reset to the default condition can be initiated by a power-up cycle of VDDDIG.

The CDC3S04 operates from two 1.8-V supplies. There is a core supply (VDDDIG/GNDDIG) for the core logic and a low-noise analog supply (VDDANA/GNDANA) for the sine-wave outputs. The CDC3S04 is designed for sequence-less power up. Both supply voltages may be applied in any order.

The CDC3S04 is offered in a 0.4-mm pitch WCSP package (1.6 mm × 2 mm) and is optimized for low standby current (0.5 µA). It is characterized for operation from –40°C to 85°C.