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Features
* * * * * * * * * * * *
Current-controlled Output Current Source with 4 Input Channels LVDS Compatible Inputs Channel 2, 3, and 4 with On-chip 100 Termination Separate Read-Channel Enable Two Selectable Outputs for Grounded Laser Diodes Output Current per Channel up to 350 mA Total Output Current up to 500 mA On-chip RF Oscillator Control of 2 Different Swings and Frequencies by Use of 4 External Resistors Oscillator Frequency Range from 200 MHz to 500 MHz Maximum Oscillator Current Amplitude 100 mApp Single 5 V Power Supply Small Pb-free QFN24 Package (4 mm x 4 mm)
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Applications
* DVD+RW with CD-RW Capability * DVD-RW with CD-RW Capability * Recordable Optical Drives
Description
The ATR0844 is a laser diode driver designed to operate two different grounded laser diodes for DVD-RW/+RW (650 nm) and CD-RW (780 nm). The device includes four channels for four different optical power levels. The write channels (channel 2 to 4) can be controlled either by fast LVDS (Low Voltage Differential Signaling) or by singleended standard CMOS logic. In case of single-ended use, each of the ENABLE inputs (NEx or Ex) can be used, the complementary input may be left open. There is no need for blocking or connection to a reference voltage. The function of the read channel is to generate a continuous output current, channels 2 to 4 are designed as write channels with very fast switching speed. All channels are summed together and routed to one of the two outputs, IOUTA or IOUTB, controlled by the select input SELA. Each write channel (channels 2 to 4) can contribute up to 350 mA to the total output current of up to 500 mA. The read channel can contribute up to 150 mA. Total gain of 100 (read channel) and 250 (channel 2, 3 and 4), respectively, are provided between each reference current input and the selected output. Although the reference inputs are current inputs, voltage control is possible by using external resistors. An on-chip RF oscillator is available to reduce laser-mode hopping noise during read mode. The oscillator current amplitude can be set independently for the two selectable outputs with two different resistors. Oscillation is enabled by a high signal at the ENOSC pin. Complete shut-down of the output currents is achieved by a low signal at the ENABLE input. In case of uncertain (balanced) enable signals, a built-in protection circuit keeps the laser diode output current within the defined range.
4-channel Laser Driver with 2 Outputs and 3 LVDS Inputs, NER Enable, On Chip Termination ATR0844 Summary
Rev. 4821AS-DVD-08/04
Figure 1. Block Diagram
I4 E4 NE4 Channel 4
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I3 E3 NE3
Channel 3
IOUTA IOUTB I2 E2 NE2 Channel 2
IR NER Channel 1 Read channel
ENABLE RF oscillator ENOSC
RFA RFB RSA RSB
SELA
2
ATR0844
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ATR0844
Pin Configuration
Figure 2. Pinning QFN24
I4 I3 I2 IR VCC VCC
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RFB RFA E2 NE2 E3 NE3
1 2 3 4 5 6
24 23 22 21 20 19 18 IOUTA 17
NER
16 RSA 15 RSB 14 IOUTB 78 13 SELA 9 10 11 12
Pin Description
Pin 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Paddle Symbol RFB RFA E2 NE2 E3 NE3 E4 NE4 ENOSC ENABLE VCC VCC SELA IOUTB RSB RSA NER IOUTA VCC VCC IR I2 I3 I4 GND Type Analog Analog Digital Digital Digital Digital Digital Digital Digital Digital Supply Supply Digital Analog Analog Analog Supply Analog Supply Supply Analog Analog Analog Analog Supply Function External resistor to ground sets frequency of oscillator B External resistor to ground sets frequency of oscillator A +LVDS control of channel 2 -LVDS control of channel 2 +LVDS control of channel 3 -LVDS control of channel 3 +LVDS control of channel 4 -LVDS control of channel 4 (low active) Enables RF oscillator (high active) Enables output current (high active) +5 V power supply +5 V power supply High: selects IOUTA, RSA, RFA Low: selects IOUTB, RSB, RFB Output current source B for laser diode External resistor to ground sets swing of oscillator B External resistor to ground sets swing of oscillator A Digital control of read channel (channel 1), active low Output current source A for laser diode +5 V power supply +5 V power supply Reference current input read channel (input impedance 500 to ground) Reference current input channel 2 (input impedance 500 to ground) Reference current input channel 3 (input impedance 500 to ground) Reference current input channel 4 (input impedance 500 to ground) Ground
E4 NE4 ENOSC ENABLE VCC VCC
3
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Absolute Maximum Ratings
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Parameters Supply voltage Input voltage at any input Power dissipation Output voltage Junction temperature Storage temperature Notes: 1. RthJA 115 K/W at Tamb = 70C 2. RthJA 115 K/W at Tamb = 25C Symbol VCC Vin Pmax Vout Tj Tstg Value -0.5 to +6.1 -0.5 to VCC + 0.5 0.7
(1)
Unit V V W V C C
to 1
(2)
-0.5 to VCC - 1 150 -65 to +125
Thermal Resistance
Parameters Junction ambient, QFN24 Note: Symbol RthJA Value 50(1) Unit K/W
1. Measured with multi-layer test board (JDEC standard)
Recommended Operating Range
Parameters Supply voltage Input current External resistor to GND to set oscillator frequency External resistor to GND to set oscillator swing Operating temperature range Symbol VCC IIR, II2, II3, II4 RFA, RFB RSA, RSB Tamb Value 4.5 to 5.9 < 1.5 >3 >1 0 to +70 Unit V mA k k C
4
ATR0844
4821AS-DVD-08/04
ATR0844
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Ordering Information
Extended Type Number ATR0844-PFQG Package Pb-free QFN24, 4 mm x 4 mm Remarks Taped and reeled
Package Information
5
4821AS-DVD-08/04
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4821AS-DVD-08/04

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