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i7110
300 Mbps LED Drivers Data Sheet
iCreate Technologies Corporation
(c) 2005 iCreate Technologies Corporation APD-8011-001
i7110
(c) Copyright 2005 iCreate Technologies Corporation
Information contained in this publication is intended through suggestion only and may be superseded by updates. No liability is assumed by iCreate Technologies Corporation with respect to the use of such information or otherwise and no representation or warranty is given. Use of iCreate's products as critical components in life support systems is not authorized. No part of this document may be reproduced or transmitted in any form or by any means for any purpose without the permission of iCreate. No licenses are conveyed, implicitly or otherwise, under any intellectual property rights. The iCreate logo and name are registered trademarks of iCreate Technologies Corporation. All rights reserved. All other trademarks mentioned herein are the property of their respective companies.
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Objective Specification Advance Information Preliminary
Description
The objective specification contains data for new product development. The information is on products in the design phase. Your designs should not be finalized with this information. This is preliminary information on new products but not yet fully characterized. The specifications in these data sheets are subject to change in any manner without notice. Information contained in the data sheet is on products in full production.
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For more information please contact: iCreate Technologies Corporation No. 6, Technology Rd. V, Science-Based Industrial Park, Hsinchu, Taiwan 300 Phone +886-3-579-0000 Fax +886-3-579-0077 e-mail support@icreate.com.tw
Revision3.00 Date05/2005
(c) 2005 iCreate Technologies Corporation APD-8011-001
i7110
+3.3V to +5.0V, 300Mbps LED Driver 1 Introduction
1.2 Applications
FDDI SDH STM-1 SONET OC-3 Fast Ethernet Fiber Channel
1.1 General Description
The i7110 is a high-speed LED driver designed for low-cost optical fiber based transmission systems. Data rates up to 300Mbps can be achieved depending on the LED used. The differential PECL inputs can be shaped by applying resistors between pulse width adjustment pins and ground. This adjustment is continuous over a 500ps range to compensate the LED unbalanced `turn on' and `turn off' time. A peaking and clamp circuit is implemented in i7110 to enhance speed performance and connecting external RC network performs this function. The i7110 can switch a wide range of current 5mA to 120mA into typical LEDs. To minimize the effects of temperature on LED output power, the device's modulation current can be set via two external resistors to increase with a temperature coefficient from 800ppm/ to 10000ppm/. Complementary current outputs help to maintain a constant supply current, reducing EMI and supply noise generated by the transmitter module, and the current is disabled if pin Disa is Pulled high. The i7110 is packaged in QSOP16 and TSSOP20.
1.3 Features
Data rates up to 300 Mbps, depending on LED. +5 V to +3.3 V operation. Programmable output current from 5mA to 120mA. Peaking circuit giving rise and fall time < 700ps. Clamping circuit enhances turn off time. Resistor programmable compensation for temperature dependence of LED output. PECL input with optional pulse width adjustment. Support most LED types. Support output current disable ability. Single Chip solution, available in TSSOP20 or QSOP16.
1.4 Ordering Information
Part no. I7110-ES i7110-EG i7110-EP Package 16-pin QSOP 16-pin QSOP 20-pin TSSOP
* i7110-EG is provided in green package
(c) 2005 iCreate Technologies Corporation
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i7110
2 Pin Configuration and Definition
2.1 Pin Configuration
QSOP16
PWAN PWAP DINP DINN VREF RSET2 RSET1 VDDA GNDA DISA IOUTB IOUT IOUT PEAK VDDC VDDD
TSSOP20
NC PWAN PWAP DINP DINN VREF RSET2 RSET1 VDDA NC NC GNDA DISA IOUTB IOUT IOUT PEAK VDDC VDDD NC
I7110-ES
I7110-EP
Figure 1. i7110 pin configuration
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(c) 2005 iCreate Technologies Corporation APD-8011-001
i7110
2.2 Pin Definition
Pin Name NC PWAN PWAP DINP DINN VREF RSET2 RSET1 VDDA NC NC VDDD VDDC PEAK IOUT IOUTB DISA GNDA
TSSOP20 Pin No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15,16 17 18 19
QSOP16 Pin No. 1 2 3 4 5 6 7 8 9 10 11 12,13 14 15 16 Not connected
Description
Inverse pulse width adjustment input Differential pulse width adjustment input. Allows continuous adjustment of input data pulse width Non inverting data input pin Inverting data input pin Input reference voltage. Connect VREF to DINN for single ended input Temperature compensation adjustment pin. Allows temperature dependence of LED light output to be reduced or removed Set nominal LED drive current Power pin, connect to most positive supply Not connected Not connected Power pin, connect to most positive supply LED shorting pin, connect to most positive supply. Speeds LED switch off Connection for pre-emphasis or peaking circuit Driver output Connect a resistor between this pin and VCC Control pin for disable current-out Ground pin
(c) 2005 iCreate Technologies Corporation
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i7110
3 Block Diagram
P W A P P W A N G N D A D IS A
D IN P D IN N
In p u t B u ffe r
P u ls e W id th A d ju s t
IO U T B
D riv e r
IO U T
VREF
Bandgap & B ia s C irc u it C u rre n t M o d u la tio n P e a k in g & C la m p in g PEAK
RSET2
RSET1
VDDA
VDDD
VDDC
Figure 2. i7110 block diagram
4
Electrical Specifications
4.1 Recommended Operating Conditions
Parameter Power Supply Operating Ambient
Symbol VCC TA
Rating 3.0 to 5.5 -40 to 85
Unit V
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(c) 2005 iCreate Technologies Corporation APD-8011-001
i7110
4.2 DC Electrical Characteristics
( VCC = 3.0 V to 5.5 V, TA = -40 to 85 , unless otherwise noted. Temperature coefficients are referenced to TA = +25. Typical values are at TA = +25, VCC = 3.3V )
Symbol VIN_H VIN_L IOUT_ON IOUT_OFF VREF VLEDH
Parameter Input high voltage level Input low voltage level LED drive current LED off current Voltage reference LED headroom voltage
Min VCC-1.0 VCC-2.0 5 VCC-1.6 -
Typ VCC-1.4 -
Max VCC-0.8 VCC-1.8 120 50 VCC-1.03 2
Units V V mA uA V V
4.3 AC Electrical Characteristics
( VCC = 3.0 V to 5.5 V, TA = -40 to 85 , unless otherwise noted. Temperature coefficients are
referenced to TA = +25. Typical values are at TA = +25, VCC = 3.3V )
Symbol LED tR LED tF PEAK tR PEAK tF IDD
Parameter LED drive rise time LED drive fall time Peaking current rise time Peaking current fall time Supply current
Min -
Typ 0.7 0.7 ILED+10
Max 1 1 1 1 ILED+20
Units ns ns ns ns mA
(c) 2005 iCreate Technologies Corporation
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i7110
4.4 Typical Operating Curve
(I7110 characteristic curve tested at VCC=3.3V , 5V. IOUT, IOUTB connect 10 resistor to VCC, VREF is floating , DINP connects to VCC, DINN connects to GND) Modulation Current VS RSET1VCC=3.3V Modulation Current VS RSET2 VCC=3.3V
Figure 3 Modulation Current VS RSET1 VCC=5V
Figure 5 Modulation Current VS RSET2 VCC=5V
Figure 4
Figure 6
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(c) 2005 iCreate Technologies Corporation APD-8011-001
i7110
4.5 Temperature Compensation Contour Plot
(I7110 characteristic curve , relationship between modulation current with RSET1 & RSET2. IOUT, IOUTB connect 10 resistor to VCC, VREF is floating , DINP connects to VCC, DINN connects to GND )
100000
100000
10mA
10mA
RRSET1(ohm)
10000
40mA 60mA 80mA 100mA 120mA
RRSET2(ohm)
10000
60mA
40mA
80mA 100mA 120mA
1000 100 1000 RRSET2(ohm) 10000 100000
1000 100 1000 RRSET2(ohm) 10000 100000
Figure7. Tj = 50 degree
100000
Figure8. Tj = 75egree
100000
10mA
10mA
RRSET1(ohm)
RRSET1(ohm)
10000
60mA
40mA
10000
60mA
40mA
80mA 100mA 120mA 100mA
80mA 120mA
1000 100 1000 RRSET2(ohm) 10000 100000
1000 100 1000 RRSET2(ohm) 10000 100000
Figure 9. Tj = 100degree
Figure 10 Tj = 125 degree
(c) 2005 iCreate Technologies Corporation
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i7110
4.6 Detail Description
The i7110 provides a flexible current drive for the modulation of the light-emitting diodes(LEDS). The circuit is designed to use 3.3V ~ 5V power supply. The IC provides up to 120mA of modulation current. Figure-11 shows a typical block diagram of i7110, which comprises a bandgap, current modulation block, peaking and clamping block, an input buffer, pulse width adjustment function block and the output driver. The VREF is used to simplify the PECLcompatible input. For single-ended operation, connect the input signal to DINP, and connect DINN directly to VREF. The VREF circuit is not designed to drive other external circuitry.
LED Drive and Temperature Compensation The two resistors RRSET1 and RRSET2 set the LED drive current and temperature compensation. The simplified application diagram (Figure-11) shows RRSET1 connects between RSET1 and GND, and RRSET2 connects between RSET1 and RSET2.
Reference-Voltage Generate The reference-voltage generator circuit provides single-ended input reference voltage VREF.
PW AP
PW AN
GND
GND
D IS A
D IN P In p u t B u ffe r D IN N Bandgap VREF RSET2 C u rre n t M o d u la tio n
P u ls e w id th A d ju s t
IO U T B
D riv e r
IO U T
RPEAK CPEAK
P e a k in g & C la m p in g
PEAK
RRSET2
RSET1
RRSET1
VDDA
VDDD
VDDC
Figure-11
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(c) 2005 iCreate Technologies Corporation APD-8011-001
i7110
7000ppm
3500ppm
Figure-12 The current flows out of the RSET1 pin determine the LED drive current. The temperature independent LED driving current is set mainly by RRSET1, while the temperature dependent current is set mainly by RRSET2. However RRSET1 and RRSET2 are not independent. The RSET2 pin connects to an internal diode in the IC, which exhibits standard diode behavior with temperature. As temperature rises, the voltage on RSET2 drops, the current flows through diode increases and the LED drive current increases. Given the various interdependencies of the drive current, RRSET1 and RRSET2, the relationship with temperature compensation is plotted in Figure-12 floating. Two external components are required to implement peaking. As shown in figure-11. When the LED is turned on, the voltage on peak is pulled low very rapidly. This voltage transient is coupled through RPAEK and CPEAK and exerts a transient current on the LED. When the LED is turned off, the voltage on PEAK is pulled high very rapidly. This Voltage transient is coupled through RPEAK and CPEAK and exerts a transient current in the opposite direction on the LED. The transient current amplitude and RC decay are calculated approximately by:
Peak current (Amps): VCC / (RPEAK+3.8) Decay (seconds): CPEAK*(RPEAK+3.8) Typical value for CPEAK and RPEAK at 3.3V operation are: CPEAK = 20 pf
Peaking Function To improve LED `turn on' time an optional function `peaking' is included in `i7110'. If this is not required, then the pin PEAK should be left
RPEAK = 10 ohm
(c) 2005 iCreate Technologies Corporation
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i7110
LED Clamping, Laser Driving Since most LEDs exhibit a longer `turn off' time than `turn on' time, a clamping function is included on the i7110 in order to reduce the `turn off' time. And the function is enabled by simply connecting pin VDDC to VCC. The disadvantage of clamping is that the LED's internal capacitance must be fully charged again before the LED starts to emit light. This will delay the turn on time of LED especially when LED drive current is low. Use of peaking function will reduce the `turn on' delay. The combination of peaking and clamping results in very fast `turn on' and `turn off' speed for the LED. When driving lasers, it will often be helpful to disable this clamping. This can be achieved by leaving the VDDC connections floating.
Continuously over a -500ps to +500ps range. The maximum difference between PWAP and PWAN is 1v. PWAP and PWAN will settle at a voltage equal to (0.76*VCC) if left floating. It is recommended that adjustment be implemented by pull down resistors on PWAP and PWAN. However it is common for one or other pin to be tied to ground for maximum adjustment.
LED Drive Pulse Width Adjustment (PWA) The input signal pulse width can be adjusted before the output stage. The differential voltage on the PWA pins shapes the input pulse
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(c) 2005 iCreate Technologies Corporation APD-8011-001
i7110
5 Typical Application Circuits
5.1 QSSOP16 Application Circuit
U1 R4 Rn R5 Rp 1 2 3 4 C6 10nF 5 6 R6 Rset2 VCC R8 Rset1 C4 0.01uF C5 0.1uF i7110_QSOP16 7 8 16 15 14 13 12 11 10 09 R2 VCC C1 VCC VCC C6 0.1uF D1 LED
PWAN PWAP DINP DINN VREF REST2 REST1 VDDA
GND DISA IOUTB IOUT IOUT PEAK VDDC VDDD
R1 22R
DIN+ DIN-
C2 0.1uF
C3 0.01uF
undershoot / overshoot can be optimized by C1 & R2. Typical C1=20pF ; R2=0 ohm @3V. Typical C1=10pF ; R2=100 ohm @5V. Rest2 : Temperature compensation adjustment. Rest1 : Set nominal LED drive current. Rn & Rp : Pulse width adjustment.
Figure 13.
(c) 2005 iCreate Technologies Corporation
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i7110
5.2 TSSOP20 Application Circuit
U1 1 R4 Rn R5 Rp 2 3 4 5 C6 10nF 6 7 R6 Rset2 VCC R8 Rset1 C4 0.01uF C5 0.1uF 8 9 10 20 19 18 17 16 15 14 13 12 11 R2 VCC C1 VCC VCC C6 0.1uF D1 LED
NC PWAN PWAP DINP DINN VREF REST2 REST1 VDDA NC
NC GND DISA IOUTB IOUT IOUT PEAK VDDC VDDD NC
R1 22R
DIN+ DIN-
C2 0.1uF
C3 0.01uF
i7110_TSSOP20
undershoot / overshoot can be optimized by C1 & R2. Typical C1=20pF ; R2=0 ohm @3V. Typical C1=10pF ; R2=100 ohm @5V. Rest2 : Temperature compensation adjustment. Rest1 : Set nominal LED drive current. Rn & Rp : Pulse width adjustment.
Figure 14
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(c) 2005 iCreate Technologies Corporation APD-8011-001
i7110
6
Package Outline
6.1 Package Outline - 16-pin QSOP
(c) 2005 iCreate Technologies Corporation
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i7110
6.2 Package Outline - 20-pin TSSOP
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(c) 2005 iCreate Technologies Corporation APD-8011-001
i7110
iCreate Technologies Corporation No. 6, Technology Rd. V, Science-Based Industrial Park, Hsinchu, Taiwan 30077, R.O.C. Tel: +886-3-579-0000 Fax: +886-3-579-0077
(c) 2005 iCreate Technologies Corporation
Page 15 APD-8011-001

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