Rev. 4815ASDVD09/04
Features
·
Current-controlled Output Current Source with 4 Input Channels
·
LVDS/CMOS Compatible Inputs Channel 2, 3, and 4
·
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
×
4 mm)
Applications
·
DVD-RAM/DVD-RW/DVD+RW with CD-RW Capability
·
Recordable Optical Drives
Description
The ATR0840 is a laser diode driver designed to operate two differently 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 sin-
gle-ended 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), respec-
tively, 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
ATR0840
Summary
2
ATR0840
4815ASDVD09/04
Figure 1. Block Diagram
Channel 3
Channel 2
Channel 1
Read channel
RF oscillator
Channel 4
I4
E4
NE4
I3
E3
NE3
I2
E2
NE2
IR
ENABLE
RFA
RFB RSA RSB
SELA
IOUTA
IOUTB
ENOSC
3
ATR0840
4815ASDVD09/04
Pin Configuration
Figure 2. Pinning QFN24
RFB
RFA
E2
NE2
E3
NE3
IOUTA
GND
RSA
RSB
IOUTB
SELA
I4
I3
I2
IR
VC
C
VC
C
E4
NE4
EN
O
S
C
EN
ABL
E
VC
C
VC
C
24 23 22 21 20 19
7 8 9 10 11 12
18
17
16
15
14
13
1
2
3
4
5
6
Pin Description
Pin
Symbol
Type
Function
1
RFB
Analog
External resistor to ground sets frequency of oscillator B
2
RFA
Analog
External resistor to ground sets frequency of oscillator A
3
E2
Digital
Digital control of channel 2 (high active)
4
NE2
Digital
Digital control of channel 2 (low active)
5
E3
Digital
Digital control of channel 3 (high active)
6
NE3
Digital
Digital control of channel 3 (low active)
7
E4
Digital
Digital control of channel 4 (high active)
8
NE4
Digital
Digital control of channel 4 (low active)
9
ENOSC
Digital
Enables RF oscillator (high active)
10
ENABLE
Digital
Enables output current (high active)
11
VCC
Supply
+5 V power supply
12
VCC
Supply
+5 V power supply
13
SELA
Digital
High: selects IOUTA, RSA, RFA
Low: selects IOUTB, RSB, RFA
14
IOUTB
Analog
Output current source B for laser diode
15
RSB
Analog
External resistor to ground sets swing of oscillator B
16
RSA
Analog
External resistor to ground sets swing of oscillator A
17
GND
Supply
Ground
18
IOUTA
Analog
Output current source A for laser diode
19
VCC
Supply
+5 V power supply
20
VCC
Supply
+5 V power supply
21
IR
Analog
Reference current input read channel (input impedance 500
to ground)
22
I2
Analog
Reference current input channel 2 (input impedance 500
to ground)
23
I3
Analog
Reference current input channel 3 (input impedance 500
to ground)
24
I4
Analog
Reference current input channel 4 (input impedance 500
to ground)
Paddle
GND
Supply
Ground
4
ATR0840
4815ASDVD09/04
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
Symbol
Value
Unit
Supply voltage
V
CC
-0.5 to +6.1
V
Input voltage at any input
V
in
-0.5 to V
CC
+ 0.5
V
Power dissipation
P
max
0.7
(1)
to 1
(2)
W
Output voltage
V
out
-0.5 to V
CC
- 1
V
Junction temperature
T
j
150
°
C
Storage temperature
T
stg
-65 to +125
°
C
Notes:
1. R
thJA
115 K/W at T
amb
= 70
°
C
2. R
thJA
115 K/W at T
amb
= 25
°
C
Thermal Resistance
Parameters
Symbol
Value
Unit
Junction ambient, QFN24
R
thJA
50
(1)
K/W
Note:
1. Measured with multi-layer test board (JDEC standard)
Recommended Operating Range
Parameters
Symbol
Value
Unit
Supply voltage
V
CC
4.5 to 5.9
V
Input current
I
IR
, I
I2
, I
I3,
I
I4
< 1.5
mA
External resistor to GND to set oscillator frequency
RFA, RFB
> 3
k
External resistor to GND to set oscillator swing
RSA, RSB
> 1
k
Operating temperature range
T
amb
0 to +70
°
C
5
ATR0840
4815ASDVD09/04
Package Information
Ordering Information
Extended Type Number
Package
Remarks
ATR0840-PFQG
Lead free QFN24, 4 mm
×
4 mm
Taped and reeled
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