Overview
The CDCM1804, produced by Texas Instruments, is a versatile clock buffer and divider chip designed for high-speed clock distribution applications. This device operates over a temperature range of –40°C to 85°C and is packaged in a 24-terminal QFN package (4 mm × 4 mm). It distributes one differential clock input to three LVPECL differential clock outputs and one single-ended LVCMOS output, making it suitable for various clocking needs in electronic systems.
Key Specifications
| Parameter | Min | Typ | Max | Unit |
|---|---|---|---|---|
| Supply Voltage (VDD) | 3 | 3.3 | 3.6 | V |
| Operating Temperature (TA) | –40 | 85 | °C | |
| Input Frequency (fclk) for LVPECL | 0 | 800 | MHz | |
| Input Frequency (fclk) for LVCMOS | 0 | 200 | MHz | |
| Output Skew for LVPECL | 15 | ps | ||
| Output Skew Between LVCMOS and LVPECL | 1.3 | 1.6 | 2.1 | ns |
| Input Voltage Swing (VIN) | 150 | 1300 | mV | |
| Input Impedance (RIN) | 300 | kΩ | ||
| Supply Current (IDD) at 3.3V, 25°C | 160 | mA |
Key Features
- Distributes one differential clock input to three LVPECL differential clock outputs and one single-ended LVCMOS output.
- Programmable output divider for two LVPECL outputs and the LVCMOS output.
- Low-output skew of 15 ps (typical) for LVPECL outputs and 1.6 ns between LVCMOS and LVPECL transitions.
- Accepts various differential signaling inputs: LVDS, HSTL, CML, VML, SSTL-2, and single-ended: LVTTL/LVCMOS.
- Provides VBB bias voltage output for single-ended input signals.
- Receiver input threshold of ±75 mV.
- Three control terminals (S0, S1, S2) and an enable terminal (EN) for selecting different output mode settings.
- 24-terminal QFN package (4 mm × 4 mm).
Applications
The CDCM1804 is designed for use in various high-speed clock distribution applications, including:
- Telecommunication systems
- Data communication equipment
- High-speed computing systems
- Networking equipment
- Other applications requiring precise clock distribution and low skew.
Q & A
- What is the operating temperature range of the CDCM1804?
The CDCM1804 operates over a temperature range of –40°C to 85°C.
- What types of differential signaling inputs does the CDCM1804 accept?
The CDCM1804 accepts various differential signaling inputs including LVDS, HSTL, CML, VML, SSTL-2, and single-ended: LVTTL/LVCMOS.
- How many output configurations are possible with the CDCM1804?
The CDCM1804 has three control terminals (S0, S1, S2) and an enable terminal (EN), allowing for up to 54 different output configurations.
- What is the typical output skew for LVPECL outputs?
The typical output skew for LVPECL outputs is 15 ps.
- What is the maximum frequency for LVPECL and LVCMOS outputs?
The maximum frequency for LVPECL outputs is 800 MHz, and for LVCMOS outputs, it is 200 MHz.
- How does the CDCM1804 handle unused outputs?
Unused outputs can be left open to save power and minimize noise impact to the remaining outputs.
- What is the purpose of the VBB output terminal?
The VBB output terminal provides a common-mode voltage reference for single-ended input signals.
- What is the recommended PCB design consideration for thermal functionality?
Special care should be taken in PCB design to ensure good thermal flow from the QFN-24 terminal package to the PCB.
- What is the maximum junction temperature of the CDCM1804?
The maximum junction temperature of the CDCM1804 is 125°C.
- What is the electrostatic discharge (ESD) rating of the CDCM1804?
The CDCM1804 has an ESD rating of >2000 V (HBM 1.5 kΩ, 100 pF).
