Datasheet

ManualsBrandsANALOG DEVICES ManualsPMICsPMIC - laser controller Laser diode driver LFCSP-32-VQ Surface-mount

3.3 V Dual-Loop 50 Mbps to 1.25 Gbps

Laser Diode Driver

Data Sheet

ADN2848

Rev. B Document Feedback

Information furnished by Analog Devices is believed to be accurate and reliable. However, no

responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other

rights of third parties that may result from its use. Specifications subject to change without notice. No

license is granted by implication or otherwise under any patent or patent rights of Analog Devices.

Trademarks and registered trademarks are the property of their respective owners.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.

Technical Support www.analog.com

FEATURES

50 Mbps to 1.25 Gbps operation

Single 3.3 V operation

Bias current range: 2 to 100 mA

Modulation current range: 5 to 80 mA

Monitor photo diode current: 50 μA to 1200 μA

50 mA supply current at 3.3 V

Closed-loop control of power and extinction ratio

Full current parameter monitoring

Laser fail and laser degrade alarms

Automatic laser shutdown (ALS)

Optional clocked data

Supports FEC rates

32-lead, 5 mm × 5 mm LFCSP_VQ package

APPLICATIONS

SONET OC-1/3/12/24

SDH STM-0/1/4

Fibre Channel

Gigabit Ethernet

GENERAL DESCRIPTION

The ADN2848 uses a unique control algorithm to control both

the average power and the extinction ratio of the laser diode

(LD) after initial factory setup. External component count and

PCB area are low because both power and extinction ratio

control are fully integrated. Programmable alarms are provided

for laser fail (end of life) and laser degrade (impending fail).

FUNCTIONAL BLOCK DIAGRAM

GND

DATAP

DATAN

CLKP

CLKN

IMODP

BIAS

ASET

ADN2848

BIAS

MOD

GND

CONTROL

IMPD

PSET

ERSET

LBWSET

ERCAP

PAVCAP

GND

CLKSEL

IMODN

DEGRADE

FAIL

ALS

IMPDMON

IMMON

IBMON

MPD

02746-001

Figure 1.

Summary of content (12 pages)

PAGE 1
3.3 V Dual-Loop 50 Mbps to 1.25 Gbps Laser Diode Driver ADN2848 Data Sheet FEATURES GENERAL DESCRIPTION 50 Mbps to 1.25 Gbps operation Single 3.3 V operation Bias current range: 2 to 100 mA Modulation current range: 5 to 80 mA Monitor photo diode current: 50 μA to 1200 μA 50 mA supply current at 3.
PAGE 2
ADN2848 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Alarms .............................................................................................7 Applications ....................................................................................... 1 Monitor Currents ..........................................................................8 General Description .............................................
PAGE 3
Data Sheet ADN2848 SPECIFICATIONS VCC = 3.0 V to 3.6 V. All specifications TMIN to TMAX, unless otherwise noted.1 Typical values are specified at 25°C. Table 1.
PAGE 4
ADN2848 Data Sheet Parameter SUPPLY ICC 5 VCC 6 Min Typ Max Unit Conditions/Comments 50 3.3 3.6 mA V IBIAS = IMOD = 0 3.0 Temperature range is −40°C to +85°C. Measured into a 25 Ω load using a 0-1 pattern at 622 Mbps. When the voltage on DATAP is greater than the voltage on DATAN, the modulation current flows in the IMODP pin. 4 Guaranteed by design and characterization. Not production tested. 5 ICCMIN for power calculation on Page 9 is the typical ICC given.
PAGE 5
Data Sheet ADN2848 ABSOLUTE MAXIMUM RATINGS Table 2. Parameter VCC to GND Digital Inputs (ALS, LBWSET, CLKSEL) IMODN, IMODP Operating Temperature Range Industrial Storage Temperature Range Junction Temperature (TJ Max) 32-Lead LFCSP_VQ Package Power Dissipation1 θJA Thermal Impedance2 Lead Temperature (Soldering for 10 sec) 1 2 Rating 4.2 V −0.3 V to VCC + 0.3 V VCC + 1.
PAGE 6
ADN2848 Data Sheet 32 CCBIAS 31 IBIAS 30 GND2 29 GND2 28 IMODP 27 GND2 26 IMODN 25 VCC2 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS 1 2 3 4 5 6 7 8 PIN 1 INDICATOR ADN2848 TOP VIEW (Not to Scale) 24 IBMON 23 IMMON 22 GND3 21 VCC3 20 ALS 19 FAIL 18 DEGRADE 17 CLKSEL NOTES 1. THE EXPOSED PAD ON THE BOTTOM OF THE PACKAGE MUST BE CONNECTED TO THE DEVICE GND. 02746-003 ERCAP PAVCAP VCC1 DATAN DATAP GND1 CLKP CLKN 9 10 11 12 13 14 15 16 LBWSET ASET ERSET PSET IMPD IMPDMON GND4 VCC4 Figure 3.
PAGE 7
Data Sheet ADN2848 THEORY OF OPERATION A laser diode (LD) has current-in to light-out transfer functions, as shown in Figure 4. Two key characteristics of this transfer function are the threshold current, ITH, and slope in the linear region beyond the threshold current, referred to as slope efficiency, or LI. ER = PAV = IAV is the average MPD current. PCW is the dc optical power specified on the laser data sheet. IMPD_CW is the MPD current at that specified PCW.
PAGE 8
ADN2848 Data Sheet Example: ADN2848 I FAIL = 50 mA so I DEGRADE = 45 mA I FAIL = 100 100 TO FLIP-FLOPS DATAN = 500 μA 50Ω 50Ω VREG 1.2 V 1.2 = = 2.4 kΩ RASET * = I ASET 500 μA R R = 2.5kΩ, DATA R = 3kΩ, CLK *The smallest valid value for RASET is 1.2 kΩ, because this corresponds to the maximum IBIAS of 100 mA.
PAGE 9
Data Sheet ADN2848 P = VCC × ICC + (IBIAS × VBIAS_PIN) + IMOD (VMODP_PIN + VMODN_PIN)/2 Caution must be used when choosing component values for ac coupling to ensure that the time constants (L/R and RC, see Figure 9) are sufficiently long for the data rate and the expected number of CIDs (consecutive identical digits). Failure to do this could lead to pattern dependent jitter and vertical eye closure.
PAGE 10
ADN2848 Data Sheet ALS FAIL 1kΩ 1.
PAGE 11
Data Sheet ADN2848 FAIL ALS VCC DEGRADE 1kΩ * * 17 VCC2 CLKSEL FAIL ALS VCC3 GND3 DEGRADE VCC IMMON 25 * 15kΩ 24 IBMON * VCC 1.
PAGE 12
ADN2848 Data Sheet OUTLINE DIMENSIONS 0.30 0.25 0.18 32 25 1 24 0.50 BSC 8 17 TOP VIEW 0.80 0.75 0.70 16 9 BOTTOM VIEW 0.05 MAX 0.02 NOM COPLANARITY 0.08 0.20 REF SEATING PLANE 3.25 3.10 SQ 2.95 EXPOSED PAD 0.50 0.40 0.30 PIN 1 INDICATOR 0.25 MIN FOR PROPER CONNECTION OF THE EXPOSED PAD, REFER TO THE PIN CONFIGURATION AND FUNCTION DESCRIPTIONS SECTION OF THIS DATA SHEET. COMPLIANT TO JEDEC STANDARDS MO-220-WHHD. 112408-A PIN 1 INDICATOR 5.10 5.00 SQ 4.90 Figure 12.