Laser Diode Driver The CXBT818Q is a high-speed monolithic Laser Diode Driver/Current Switch with ECL/PECL input level. Open collector outputs are provided at the output pins (Q, QBX) and have the capacity of driving modulation current of 50mAp-p at a maximum data rate of 622Mbps. Along with the modulation current generator there is the laser diode bias current generator which has capacity of sourcing up to 60mA (Bias). The laser diode bias current can be controlled by either a voltage or current into the bias adjust pin (BiasAdj) and the bias set pin (SBias), depending on how these pins are configured. Control of the bias current is achieved through the APC (Automatic Power Control) circuit. In order to avoid having a large current go through the laser diode, this IC also provides an Activity detector function for laser protection. The Activity detector circuit detects data edge transitions and if no data transition occurs after a certain period, then both the modulation and bias currents are shutdown. The bias currents are shut it down by in order to pull down the output voltage of When the automatic shutdown is conducted, it is possible to select whether the laser diode alarm output is activated or not. Additionally, this IC has the DFF for the input signal correction and the internal Duty Cycle correction circuit that can control the falling edge of the input pulse up to a maximum Absolute Maximum Ratings • Differential input voltage • Bias output current 0 to 80 mA • SBias input/output current 0 to 5 mA • Bias control current • Bbias control voltage ♦ Modulation output current 70 mA • Modulation adjust current • Storage temperature Recommended Operating Conditions • Operating ambient temperature • Maximum data rate (NRZ): 622Mbps • Alarm and Shutdown function • DFF for input signal correction • Input signal Duty cycle correction • Automatic Power Control (APC) for bias current • Activity detector function for laser protection • Alarm signal mask function during shutdown • Differential PECL inputs or AC coupled inputs Sony reserves the right to change products and specifications without prior notice. This information does not convey any license by any implication or otherwise under any patents or other right. Application circuits shown, if any, are typical examples illustrating the operation of the devices. Sony cannot assume responsibility for any problems arising out of the use of these circuits. Bipolar silicon monolithic IC

Block Diagram and Pin Configuration Duty Cycle

Equivalent circuit Positive power supply Negative power supply Bias current setting. Bias current setting or Bias current output. Open collector output. Negative power supply Modulation current Open collector output. Complementary current symmetrical output. Negative power supply Positive power supply Chip temperature

Equivalent circuit Modulation current driver compensation. Normally, connects CornpB pins. Capacitor connection (IN_ALM) operation. This pin sets the period activity detector. Activity detector circuit Activity detector selection control. High (open): (Through mode)

Equivalent circuit Differential PECL clock Negative power supply for data input circuit. Differential PECL data Positive power supply for data input circuit. Alarm signal control for optical power output forced shutdown. High (open): Alarm signal stays Window comparator top/bottom threshold The alarm (fault) assert

Equivalent circuit output current. (Shutdown input) When left open, High. Output duty cycle falling edge of the input High pulse. Variable delay limit of that is from a resistor value between compensated reference Positive power supply for alarm output circuit. laser monitor diode (Pseudo LVTTL output)

Electrical Characteristics

DC and AC Electrical Characteristics for OpAmp of APC Circuit

Description of Each Function Block 1. Data Buffer, Clock Buffer Data Buffer and Clock Buffer are comprised of the data buffer, clock buffer, DFF, MUX and delay generator. ECL/PECL data is input to the data buffer at a maximum data rate of 622Mbps. The input data DFF selection pin {Pin 19 FFSel) can select whether the input data is used in through mode or the signal which is corrected by the clock signal in the DFF is used. When the FFSel is open, the data becomes through mode, when the FFsel is connected VEE.the data becomes DFF mode. And, this data is input to the delay circuit. The delay circuit...

The laser diode alarm output state can be controlled by the alarm signal control pin (Pin 26 MaskSel) for the optical power output forced shutdown. When the automatic shutdown is conducted and MaskSel pin is left open, the laser diode alarm output goes High. The laser diode alarm output is kept Low (disable) by connecting 5. Shutdown and Input Alarm Circuits These circuits disable both the modulation current and the bias current under various conditions. The function block diagram for all of the shutdown mechanisms for the circuit is shown in Fig. 5. The Shutdown circuit has complementary TTL...

DC Electrical Characteristics Measurement Circuit

AC Electrical Characteristics Measurement Circuit

Application circuits shown are typical examples illustrating the operation of the devices. Sony cannot assume responsibility for any problems arising out of the use of these circuits or for any infringement of third party patent and other right due to same.

Example of Representative Characteristics Fig. 1. Pulse width vs. Rset characteristics when 1.6ns input data pulse (622Mbps) is applied IQset characteristics Fig. 3. Bias current (I BIAS) VS. Bias adjust current (IBset) characteristics Fig. 4. Bias current (IBIAS) vs. Bias adjust voltage (VBset) characteristics Fig. 6. Input detection time vs. Ctimer characteristics DrvMon current characteristics

Single-phase input Fig. 8. Electrical Output Waveform Single-phase input Fig. 9. Optical Power Output Waveform

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