intersil X9522 DATA SHEET

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SIB

L ,

Data Sheet January 3, 2006

Laser Diode Control for Fiber Optic Modules

X9522

FN8208.1

Triple DCP, Dual Voltage Monitors

FEATURES

• Three Digitally Controlled Potentiometers (DCPs) —64 Tap - 10kΩ —100 Tap - 10kΩ —256 Tap - 100kΩ —Nonvolatile —Write Protect Function

• 2-Wire industry standard Serial Interface

• Dual Voltage Monitors —Programmable Threshold Voltages

• Single Supply Operation —2.7V to 5.5V

• Hot Pluggable

• 20 Pin package —TSSOP

BLOCK DIAGRAM

PROTECT LOGIC

DESCRIPTION

The X9522 combines three Digitally Controlled Potentiometers (DCPs), and two programmable voltage monitor inputs with software and hardware indicators. All functions of the X9522 are accessed by an industry standard 2-Wire serial interface.

Two of the DCPs of the X9522 may be utilized to control the bias and modulation currents of the laser diode in a Fiber Optic module. The third DCP may be used to set other various reference quantities, or as a coarse trim for one of the other two DCPs.The programmable voltage monitors may be used for monitoring various module alarm levels.

The features of the X9522 are ideally suited to simplifying the design of fiber optic modules. The integration of these functions into one package significantly reduces board area, cost and increases reliability of laser diode modules.

WIPER COUNTER REGISTER

6 - BIT

NONVOLATILE

MEMORY

SDA

SCL

Vcc / V1

DATA

COMMAND DECODE & CONTROL

LOGIC

THRESHOLD

RESET LOGIC

VTRIP

WIPER COUNTER REGISTER

7 - BIT

CONSTAT

NONVOLATILE

MEMORY

WIPER COUNTER REGISTER

8 - BIT

NONVOLATILE

MEMORY

V3RO

V2RO

CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.

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| Intersil (and design) is a registered trademark of Intersil Americas Inc.

All other trademarks mentioned are the property of their respective owners.

Ordering Information

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X9522

PRESET (FACTORY SHIPPED) V

PART NUMBER PART MARKING

X9522V20I-A X9522VIA Optimized for 3.3V system monitoring -40 to +85 20 Ld TSSOP X9522V20I-B X9522VIB Optimized for 5V system monitoring -40 to +85 20 Ld TSSOP X9522V20IZ-A (Note) X9522VZIA Optimized for 3.3V system monitoring -40 to +85 20 Ld TSSOP (Pb-free) X9522V20IZ-B (Note) X9522VZIB Optimized for 5V system monitoring -40 to +85 20 Ld TSSOP (Pb-free)

*Add "T1" suffix for tape and reel. NOTE: Intersil Pb-free plus anneal products employ special Pb-free material sets; molding compounds/die attach materials and 100% matte tin plate

termination finish, which are RoHS compliant and compatible with both SnPb and Pb-free soldering operations. Intersil Pb-free products are MSL classified at Pb-free peak reflow temperatures that meet or exceed the Pb-free requirements of IPC/JEDEC J STD-020.

THRESHOLD LEVELS (x = 2, 3) TEMP RANGE (°C) PACKAGE

TRIPx

PIN CONFIGURATION

20 Pin TSSOP

W2 2

V3RO

SCL

SDA

4 5 6

7 8

20 19 18 17

16 15 14 13 12 11

Vcc / V1

V2RO V2 R

NOT TO SCALE

DETAILED DEVICE DESCRIPTION

The X9522 combines three Intersil Digitally Controlled Potentiometer (DCP) devices, and two voltage monitors, in one package. These functions are suited to the control, support, and monitoring of various system parameters in fiber optic modules. The combination of the X9522 functionality lowers system cost, increases reliability, and reduces board space requirements.

Two high resolution DCPs allow for the “set-and-forget” adjustment of Laser Driver IC parameters such as Laser Diode Bias and Modulation Currents. One lower resolution DCP may be used for setting sundry system parameters such as maximum laser output power (for eye safety requirements).

The dual Voltage Monitor circuits continuously compare their inputs to individual trip voltages. If an input voltage exceeds it’s associated trip level, a hardware output (V3RO, V2RO) are allowed to go HIGH. If the input voltage becomes lower than it’s associated trip level, the corresponding output is driven LOW. A corresponding binary representation of the two monitor circuit outputs (V2RO and V3RO) are also stored in latched, volatile (CONSTAT) register bits. The status of these two monitor outputs can be read out via the 2-wire serial port.

Intersil’s unique circuits allow for all internal trip voltages to be individually programmed with high accuracy. This gives the designer great flexibility in changing system parameters, either at the time of manufacture, or in the field.

The device features a 2-Wire interface and software pro-

tocol allowing operation on an I

C™ compatible serial

bus.

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PIN ASSIGNMENT

Pin Name Function

4V3

5V3RO

7WP

8SCL

9SDA

10 Vss Ground.

17 V2

18 V2RO

20 Vcc / V1 Supply Voltage.

6, 19 NC No Connect.

Connection to end of resistor array for (the 256 Tap) DCP 2.

Connection to terminal equivalent to the “Wiper” of a mechanical potentiometer for DCP 2.

Connection to other end of resistor array for (the 256 Tap) DCP 2.

V3 Voltage Monitor Input. V3 is the input to a non-inverting voltage comparator circuit. When the V3 input is higher than the V3 to VSS when not used.

V3 RESET Output. This open drain output makes a transition to a HIGH level when V3 is greater than

and goes LOW when V3 is less than V

TRIP3

pin requires the use of an external “pull-up” resistor.

Write Protect Control Pin. WP pin is a TTL level compatible input. When held HIGH, Write Protection is enabled. In the enabled state, this pin prevents all nonvolatile “write” operations. Also, when the Write Protection is enabled, and the DCP Write Lock feature is active (i.e. the DCP Write Lock bit is set to “1”), then no “write” (volatile or nonvolatile) operations can be performed in the device (including the wiper position of any of the integrated Digitally Controlled Potentiometers (DCPs). The WP pin uses an internal “pull-down” resistor, thus if left floating the write protection feature is disabled.

Serial Clock. This is a TTL level compatible input pin used to control the serial bus timing for data input and output.

Serial Data. SDA is a bidirectional TTL level compatible pin used to transfer data into and out of the device. The SDA pin input buffer is always active (not gated). This pin requires an external pull up resistor.

Connection to other end of resistor for (the 100 Tap) DCP 1.

Connection to terminal equivalent to the “Wiper” of a mechanical potentiometer for DCP 1.

Connection to end of resistor array for (the 100 Tap) DCP 1.

Connection to end of resistor array for (the 64 Tap) Digitally Controlled Potentiometer (DCP) 0.

Connection to terminal equivalent to the “Wiper” of a mechanical potentiometer for DCP 0.

Connection to the other end of resistor array for (the 64 Tap) DCP 0.

V2 Voltage Monitor Input. V2 is the input to a non-inverting voltage comparator circuit. When the V2 input is greater than the V2 to VSS when not used.

V2 RESET Output. This open drain output makes a transition to a HIGH level when V2 is greater than

, and goes LOW when V2 is less than V

TRIP2

pin. The V2RO pin requires the use of an external “pull-up” resistor.

threshold voltage, V3RO makes a transition to a HIGH level. Connect

TRIP3

threshold voltage, V2RO makes a transition to a HIGH level. Connect

TRIP2

. There is no delay circuitry on this pin. The V3RO

TRIP3

. There is no power-up reset delay circuitry on this

TRIP2

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SCL

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SDA

X9522

Data Stable Data Change Data Stable

Figure 1. Valid Data Changes on the SDA Bus

PRINCIPLES OF OPERATION

SERIAL INTERFACE

Serial Interface Conventions

The device supports a bidirectional bus oriented protocol. The protocol defines any device that sends data onto the bus as a transmitter, and the receiving device as the receiver. The device controlling the transfer is called the master and the device being controlled is called the slave. The master always initiates data transfers, and provides the clock for both transmit and receive operations. Therefore, the X9522 operates as a slave in all applications.

Serial Clock and Data

Data states on the SDA line can change only while SCL is LOW. SDA state changes while SCL is HIGH are reserved for indicating START and STOP conditions. See Figure 1. On power-up of the X9522, the SDA pin is in the input mode.

Serial Start Condition

All commands are preceded by the START condition, which is a HIGH to LOW transition of SDA while SCL is HIGH. The device continuously monitors the SDA and SCL lines for the START condition and does not respond to any command until this condition has been met. See Figure 2.

Serial Stop Condition

All communications must be terminated by a STOP condition, which is a LOW to HIGH transition of SDA while SCL is HIGH. The STOP condition is also used to place the device into the Standby power mode after a read sequence. A STOP condition can only be issued after the transmitting device has released the bus. See Figure 2.

Serial Acknowledge

An ACKNOWLEDGE (ACK) is a software convention used to indicate a successful data transfer. The transmitting device, either master or slave, will release the bus after transmitting eight bits. During the ninth clock cycle, the receiver will pull the SDA line LOW to ACKNOWLEDGE that it received the eight bits of data. Refer to Figure 3.

The device will respond with an ACKNOWLEDGE after recognition of a START condition if the correct Device Identifier bits are contained in the Slave Address Byte. If a write operation is selected, the device will respond with an ACKNOWLEDGE after the receipt of each subsequent eight bit word.

In the read mode, the device will transmit eight bits of data, release the SDA line, then monitor the line for an ACKNOWLEDGE. If an ACKNOWLEDGE is detected and no STOP condition is generated by the master, the device will continue to transmit data. The device will terminate further data transmissions if an ACKNOWLEDGE is not detected. The master must then issue a STOP condition to place the device into a known state.

SCL

SDA

Start Stop

Figure 2. Valid Start and Stop Conditions

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SCL

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SCL

from

Master

Data Output

from

Transmitter

Data Output

from

Receiver

X9522

81 9

Start Acknowledge

Figure 3. Acknowledge Response From Receiver

DEVICE INTERNAL ADDRESSING

Addressing Protocol Overview

The user addressable internal components of the X9522 can be split up into two main parts:

—Three Digitally Controlled Potentiometers (DCPs)

—Control and Status (CONSTAT) Register

Depending upon the operation to be performed on each of these individual parts, a 1, 2 or 3 Byte protocol is used. All operations however must begin with the Slave Address Byte being issued on the SDA pin. The Slave address selects the part of the X9522 to be addressed, and specifies if a Read or Write operation is to be performed.

It should be noted that in order to perform a write operation to a DCP, the Write Enable Latch (WEL) bit must first be set.

Slave Address Byte

Following a START condition, the master must output a Slave Address Byte (Refer to Figure 4.). This byte consists of three parts:

—The Device Type Identifier which consists of the most

significant four bits of the Slave Address (SA7 - SA4). The Device Type Identifier must always be set to 1010 in order to select the X9522.

—The next three bits (SA3 - SA1) are the Internal Device

Address bits. Setting these bits to 111 internally selects the DCP structures in the X9522. The CONSTAT Register may be selected using the Internal Device Address 010.All other bit combinations are RESERVED.

—The Least Significant Bit of the Slave Address (SA0)

Byte is the R/W

bit. This bit defines the operation to be performed on the device being addressed (as defined in the bits SA3 - SA1). When the R/W

bit is “1”, then a READ operation is selected. A “0” selects a WRITE operation (Refer to Figure 4.)

SA6SA7

SA5

1010

DEVICE TYPE

IDENTIFIER

Internal Address

(SA3 - SA1)

010

111

Others

Bit SA0 Operation

0WRITE

1 READ

SA3 SA2

SA4

INTERNAL

DEVICE

ADDRESS

Internally Addressed

Device

CONSTAT Register

DCP

RESERVED

SA1

SA0

R/W

READ / WRITE

Figure 4. Slave Address Format

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Nonvolatile Write Acknowledge Polling

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After a nonvolatile write command sequence (for either the Non Volatile Memory of a DCP (NVM), or the CONSTAT Register) has been correctly issued (including the final STOP condition), the X9522 initiates an internal high voltage write cycle. This cycle typically requires 5 ms. During this time, no further Read or Write commands can be issued to the device. Write Acknowledge Polling is used to determine when this high voltage write cycle has been completed.

To perform acknowledge polling, the master issues a START condition followed by a Slave Address Byte. The Slave Address issued must contain a valid Internal Device Address. The LSB of the Slave Address (R/W can be set to either 1 or 0 in this case. If the device is still busy with the high voltage cycle then no ACKNOWLEDGE will be returned. If the device has completed the write operation, an ACKNOWLEDGE will be returned and the host can then proceed with a read or write operation. (Refer to Figure 5.)

X9522

)

WIPER COUNTER REGISTER

(WCR)

NON

VOLATILE

MEMORY

(NVM)

DECODER

“WIPER”

FET

SWITCHES

Figure 6. DCP Internal Structure

RESISTOR

ARRAY

Byte load completed

by issuing STOP.

Enter ACK Polling

Issue START

Issue Slave Address Byte (Read or Write)

ACK

returned?

YES

High Voltage Cycle

complete. Continue

command sequence?

YES

Continue normal

Read or Write

command sequence

PROCEED

DIGITALLY CONTROLLED POTENTIOMETERS

DCP Functionality

The X9522 includes three independent resistor arrays. These arrays respectively contain 63, 99 and 255 discrete resistive segments that are connected in series. The physical ends of each array are equivalent to the

Issue STOP

fixed terminals of a mechanical potentiometer (R

inputs - where x = 0,1,2).

At both ends of each array and between each resistor

segment there is a CMOS switch connected to the wiper

) output. Within each individual array, only one

switch may be turned on at any one time. These switches are controlled by the Wiper Counter Register (WCR) (See Figure 6). The WCR is a volatile register.

Issue STOP

On power-up of the X9522, wiper position data is automatically loaded into the WCR from its associated Non Volatile Memory (NVM) Register. The Table below shows the Initial Values of the DCP WCR’s before the contents of the NVM is loaded into the WCR.

DCP Initial Values Before Recall

/ 64 TAP VH / TAP = 63

/ 100 TAP VL / TAP = 0

/ 256 TAP VH / TAP = 255

and

Figure 5. Acknowledge Polling Sequence

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January 3, 2006

Vcc

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X9522

Vcc (Max.)

TRIP

trans

Figure 7. DCP Power-up

The data in the WCR is then decoded to select and enable one of the respective FET switches. A “make before break” sequence is used internally for the FET switches when the wiper is moved from one tap position to another.

Hot Pluggability

Figure 7 shows a typical waveform that the X9522 might experience in a Hot Pluggable situation. On power-up, Vcc / V1 applied to the X9522 may exhibit some amount of ringing, before it settles to the required value.

The device is designed such that the wiper terminal

) is recalled to the correct position (as per the last

stored in the DCP NVM), when the voltage applied to Vcc / V1 exceeds V

Therefore, if t V1 to settle above V wiper terminal position is recalled by (a maximum) time:

+ tpu. It should be noted that t

trans

system hot plug conditions.

trans

for a time exceeding t

TRIP

is defined as the time taken for Vcc /

(Figure 7): then the desired

TRIP

trans

pu.

is determined by

DCP Operations

In total there are three operations that can be performed on any internal DCP structure:

—DCP Nonvolatile Write

—DCP Volatile Write

—DCP Read

A nonvolatile write to a DCP will change the “wiper position” by simultaneously writing new data to the associated WCR and NVM. Therefore, the new “wiper position” setting is recalled into the WCR after Vcc / V1 of the X9522 is powered down and then powered back up.

A volatile write operation to a DCP however, changes the “wiper position” by writing new data to the associated WCR only. The contents of the associated NVM register

Maximum Wiper Recall time

remains unchanged. Therefore, when Vcc / V1 to the device is powered down then back up, the “wiper position” reverts to that last position written to the DCP using a nonvolatile write operation.

Both volatile and nonvolatile write operations are executed using a three byte command sequence: (DCP) Slave Address Byte, Instruction Byte, followed by a Data Byte (See Figure 9).

A DCP Read operation allows the user to “read out” the current “wiper position” of the DCP, as stored in the associated WCR. This operation is executed using the Random Address Read command sequence, consisting of the (DCP) Slave Address Byte followed by an Instruction Byte and the Slave Address Byte again (Refer to Figure 10.).

Instruction Byte

While the Slave Address Byte is used to select the DCP devices, an Instruction Byte is used to determine which DCP is being addressed.

The Instruction Byte (Figure 8) is valid only when the Device Type Identifier and the Internal Device Address bits of the Slave Address are set to

1010111. In this case, the two Least Significant Bit’s (I1 - I0) of the Instruction Byte are used to select the particular DCP (0 - 2). In the case of a Write to any of the DCPs (i.e. the LSB of the Slave Address is 0), the Most Significant Bit of the Instruction Byte (I7), determines the Write Type (WT) performed.

If WT is “1”, then a Nonvolatile Write to the DCP In this case, the “wiper position” of the DCP is changed by simultaneously writing new data to the associated WCR and NVM. Therefore, the new “wiper position” setting is recalled into the WCR after Vcc / V1 of the X9522 has been powered down then powered back up.

occurs.

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X9522

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I5I6I7 I4 I3 I2 I1 I0

00WT 0 0 0 P1 P0

WRITE TYPE

†

Select a Volatile Write operation to be performed

on the DCP pointed to by bits P1 and P0

Select a Nonvolatile Write operation to be per-

formed on the DCP pointed to by bits P1 and P0

†

This bit has no effect when a Read operation is being performed.

Description

DCP SELECT

Figure 8. Instruction Byte Format

If WT is “0” then a DCP Volatile Write is performed. This operation changes the DCP “wiper position” by writing new data to the associated WCR only. The contents of the associated NVM register remains unchanged. Therefore, when Vcc / V1 to the device is powered down then back up, the “wiper position” reverts to that last written to the DCP using a nonvolatile write operation.

DCP Write Operation

A write to DCPx (x=0,1,2) can be performed using the three byte command sequence shown in Figure 9.

In order to perform a write operation on a particular DCP, the Write Enable Latch (WEL) bit of the CONSTAT Register must first be set (See “WEL: Write Enable Latch (Volatile)” on page 10.)

The Slave Address Byte 10101110 specifies that a Write to a DCP is to be conducted. An ACKNOWLEDGE is returned by the X9522 after the Slave Address, if it has been received correctly.

Next, an Instruction Byte is issued on SDA. Bits P1 and P0 of the Instruction Byte determine which WCR is to be written, while the WT bit determines if the Write is to be volatile or nonvolatile. If the Instruction Byte format is valid, another ACKNOWLEDGE is then returned by the X9522.

Following the Instruction Byte, a Data Byte is issued to the X9522 over SDA. The Data Byte contents is latched into the WCR of the DCP on the first rising edge of the clock signal, after the LSB of the Data Byte (D0) has been issued on SDA (See Figure 25).

The Data Byte determines the “wiper position” (which FET switch of the DCP resistive array is switched ON) of the DCP. The maximum value for the Data Byte depends upon which DCP is being addressed (see Table below).

P1- P0 DCPx # Taps Max. Data Byte

00 x = 0 64 3Fh

0 1 x = 1 100 Refer to Appendix 1

1 0 x = 2 256 FFh

1 1 Reserved

Using a Data Byte larger than the values specified above results in the “wiper terminal” being set to the highest tap position. The “wiper position” does NOT roll-over to the lowest tap position.

For DCP0 (64 Tap) and DCP2 (256 Tap), the Data Byte maps one to one to the “wiper position” of the DCP “wiper terminal”. Therefore, the Data Byte 00001111

) corresponds to setting the “wiper terminal” to tap

(15

position 15. Similarly, the Data Byte 00011100 (28

corresponds to setting the “wiper terminal” to tap position

28. The mapping of the Data Byte to “wiper position” data for DCP1 (100 Tap), is shown in “APPENDIX 1”. An example of a simple C language function which “translates” between the tap position (decimal) and the Data Byte (binary) for DCP1, is given in “APPENDIX 2”.

)

10101110

S T A R T

SLAVE ADDRESS BYTE

WT 0 0 0 0 0 P1 P0 A C K

INSTRUCTION BYTE

C K

Figure 9. DCP Write Command Sequence

D7 D6 D5 D4 D3 D2 D1 D0

DATA BYTE

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WRITE Operation

Signals from the Master

Slave

Address

Instruction

Byte

SDA Bus

Signals from the Slave

101 11100

“Dummy” write

00 000

A C K

Figure 10. DCP Read Sequence

It should be noted that all writes to any DCP of the X9522 are random in nature. Therefore, the Data Byte of consecutive write operations to any DCP can differ by an arbitrary number of bits. Also, setting the bits P1=1, P0=1 is a reserved sequence, and will result in no ACKNOWLEDGE after sending an Instruction Byte on SDA.

The factory default setting of all “wiper position” settings is with 00h stored in the NVM of the DCPs. This corre-

sponds to having the “wiper teminal”

(x = 0,1,2) at

the “lowest” tap position, Therefore, the resistance

between Wiper Resistance,

and RLX is a minimum (essentially only the

DCP Read Operation

A read of DCPx (x = 0,1,2) can be performed using the three byte random read command sequence shown in Figure 10.

The master issues the START condition and the Slave Address Byte 10101110 which specifies that a “dummy” write” is to be conducted. This “dummy” write operation sets which DCP is to be read (in the preceding Read operation). An ACKNOWLEDGE is returned by the X9522 after the Slave Address if received correctly. Next, an Instruction Byte is issued on SDA. Bits P1-P0 of the Instruction Byte determine which DCP “wiper position” is to be read. In this case, the state of the WT bit is “don’t care”. If the Instruction Byte format is valid, then another ACKNOWLEDGE is returned by the X9522.

READ Operation

Slave

Address

Data Byte

P 1

101 11110

A C K

MSB

t o p

“-” = DON’T CARE

LSB

DCPx

x = 0

x = 1

x = 2

Following this ACKNOWLEDGE, the master immediately issues another START condition and a valid Slave address byte with the R/W

bit set to 1. Then the X9522 issues an ACKNOWLEDGE followed by Data Byte, and finally, the master issues a STOP condition. The Data Byte read in this operation, corresponds to the “wiper position” (value of the WCR) of the DCP pointed to by bits P1 and P0.

It should be noted that when reading out the data byte for DCP0 (64 Tap), the upper two most significant bits are “unknown” bits. For DCP1 (100 Tap), the upper most significant bit is an “unknown”. For DCP2 (256 Tap) however, all bits of the data byte are relevant (See Figure 10).

CONTROL AND STATUS REGISTER

The Control and Status (CONSTAT) Register provides the user with a mechanism for changing and reading the status of various parameters of the X9522 (See Figure 11).

The CONSTAT register is a combination of both volatile and nonvolatile bits. The nonvolatile bits of the CONSTAT register retain their stored values even when Vcc / V1 is powered down, then powered back up. The volatile bits however, will always power-up to a known logic state “0” (irrespective of their value at power-down).

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