Intersil ISL41387EVAL1Z User Manual

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ISL41387EVAL1Z User’s Manual

Application Note May 30, 2006

Description

The ISL41387 evaluation board is RoHS compliant, and provides a quick and easy method for evaluating this Dual Protocol IC. The eval board also accommodates the ISL41334; see the “ISL41334EVAL1Z User’s Manual” for details.

This board was designed to allow the user to evaluate all the features available on the ISL81387 and ISL41387 products. The ISL41387 is the full featured version (see “Features” below), where the QFN package’s increased pin count gives the user access to functionality not available on the pin limited ISL81387. The same die is used in both products, so other than minor package effects, evaluating the QFN packaged ISL41387 is a reasonable substitute for evaluating the ISL81387.

By changing jumper positions the user can quickly set the board to evaluate any of the ISL41387’s many modes and features, and the input states can also be set via jumpers.

Refer to the data sheet for complete details regarding the functions and features of this device. These dual protocol ICs feature many modes, so studying the device’s truth-table along with its operating circuits and detailed description is the best way to gain an understanding of how the part works.

Features

• QFN Version Demonstrates All Enhanced Features: Logic Supply Pin (VL) Three RS-485 Speed Options - 115kbps/460kbps/20Mbps Active Low RS-485 Rx Enable for Simple Direction Control

• Quick Configuration Using Jumpers

• State of All Inputs Can be Set by Jumper Positions

• No Bus Termination Resistors; Allows RS-232 or RS-485 Evaluation

• Simple Operation Requires Only One, 5V, Power Supply

Important Notes

To facilitate locating jumpers on this board, Figure 3 is a jumper locator and, in this Application Note, the (#) following a jumper mention corresponds to the red jumper number on the locator. See the “Jumper Definitions” section for a description of the function of each jumper.

The base board is used to evaluate both the ISL41334 (2 port) and ISL41387 (1 port) products, so the jumper and connector names reflect the functionality of both products. Due to space limitations some jumper labels are abbreviated, but the corresponding BNC connector has the full label.

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In most cases, a name that applies to both products contains no parenthesis (e.g., “B1”), a name that applies to only the ISL41334 is followed by “(NC)” (e.g., “B2 (NC)”), and a name that applies to only the ISL41387 is preceded by “NC” and/or has the name in parenthesis (e.g., “NC (DEN)” or “(DEN)”).

Note that on “Rev . A” of these boards the following minor errors have been noted, and are corrected on subsequ ent revisions:

• Jumper labels “J-SELX” (not numbered) should be “J-SELX (NC)” because they are not used for the ISL41387

• Jumper label “J-RXEN2 “J-RXEN2

• Jumper label “J-RXEN” (11) should be “J-(RXEN)” because it is only used for the ISL41387

• Jumper label “J-DE2” (not numbered) should be “J-DE2 (NC)” because it is not used for the ISL41387

• Jumper label “J-DY2” (not numbered) should be “J-DY2 (NC)” because it is not used for the ISL41387

• Jumper label “J-ON/OFF “J-ON/OFF

• Jumper label “J-(SLEW)” (13) should be “J-DY1 (SLEW)”

• Jumper label “J-DE1” (14) should be “J-DZ1/DE1 (DY)”.

It is important to note that the ISLX1387 don’t follow the RS-485 convention whereby the inverting I/O is labeled “B/Z”, and the noninverting I/O is “A/Y”. Thus, the 1387 A/Y (B/Z) pins connect to the B/Z (A/Y) pins of generic RS-485/422 ICs.

Input signals that are likely to be driven by a generator connect to a BNC connector, and there is a 50Ω termination resistor to GND when the jumper is in the “LOW” position.

(NC)” because it is not used for the ISL41387

” (not numbered) should be

Default Configuration

As delivered (see “Functional Diagram”), the board is configured for powered-up (not SHDN) RS-485 mode, driver enabled, via DEN, and set for high speed (20Mbps) operation, driver input (DY) low, Rx enabled via the RXEN line, Rx inputs floating, and V this configuration, the jumpers are installed as follows (unlisted jumpers are not installed, and (#) indicates the jumper number on the Figure 3 jumper locator): A2 (485/232 RXEN1 (DZ/SLEW) (13) = VH; DZ1/DE1(DY) (14) = LOW; RXBIAS-V V

-VHIGH (17) = installed.

Note that there are no differential termination resistors on either the Rx inputs nor the Tx outputs. If these resistors are desired, they can be added at positions R9 and R7, respectively.

) (7) =VH; (DEN)(8) =VH; SPB(9) =VH;

(10) =VH; (RXEN)(11) = VH; (ON) (12) =VH;

(15) = installed; VCC-VL(16) = installed;

shorted to VCC. To achieve

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

1-888-INTERSIL or 1-888-468-3774

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

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

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Application Note 1248

Functional Diagram (Default Configuration)

+5V

0.1μF C

0.1μF

A1 B1

Y1 Z1

(16)

0.1μF

38 36

2 3

4 5

11 21

C1+

C1C2+

C2-

DEN 485 / 232

GND

15, 16

(17)

V+

V-

RXEN RXEN

SLEW

SPB

VHIGH (VH )

0.1μF

H H

VL - The logic supply voltage that sets the ISL41387’s Rx

output V points; the “VCC-VL” (16) jumper shorts this jack to V remove this jumper if supplying a voltage other than V

levels, and the logic and Tx input switching

, so

Getting Started

Connect a 5V, 500mA minimum, power supply to the VCC and GND banana jacks. It is recommended that an ammeter be used between the supply and the board, so that I be monitored. Ensure that the “RXBIAS-VCC” (15), “VCC-VL” (16) and “VL-VHIGH” (17) jumpers are installed in the upper right hand corner of the board.

External Loopback Via Jumpers

T o evaluate the Rx and Tx performance at the same time, an external loopback can be implemented simply by installing jumpers “A1/Y1_LB (5) and “B1/Z1_LB (6). In this configuration, the Tx output lines connect to the corresponding Rx input lines, so the data driven on the Tx input(s) appears at the Rx output(s). In RS-485 mode, data driven on DY loops back through A and B to R mode, DY loops back to R

, and DZ loops back to RB.

For RS-485 mode, installing resistors R7 and R9 allows evaluation of performance with the Tx driving a double terminated load.

can

. In RS-232

Supply Banana Jacks

There are eight banana jacks at the top of the board for power supply connections, but only V required connections. The function and use of each jack (from left to right) is:

VLOAD - This is a load voltage driving the load resistors connected to the Rx and Tx outputs (Tx resistors - R5 and R6 - not populated); used mostly during output enable and disable time characterizations.

GND - Common connection for any supplies used. RXBIAS - A voltage that can be applied to any or all Rx

inputs via jumpers “J9” and “J10” (3 & 2); the “RXBIAS-VCC”

(15) jumper shorts this jack to V

supplying a voltage other than V

V+ - Used to monitor the positive charge pump voltage in RS-232 mode.

V- - Used to monitor the negative charge pump voltage in RS-232 mode.

VCC - The 5V supply connection. VHIGH - Connects to all the “VH” positions on the jumpers to

define the high level voltage for logic and Tx inputs; the “VL-VHIGH” (17) jumper shorts this jack to V this jumper if supplying a voltage other than V

and GND are

, so remove this jumper if

, so remove

Basic RS-485 DC Evaluation

General Observations

should be approximately 1.6mA.

Measure V+ and V- at the banana jacks - V+ = VCC and V- = GND, indicating that the charge pumps are off for low power and low noise.

is high - due to the “full failsafe” Rx - while RB is always

tri-stated because it is unused in RS-485 mode. Note that this board isn’t populated with differential

termination resistors on either the Rx inputs nor the Tx outputs. If these resistors are desired, they can be added at positions R9 and R7, respectively.

Receiver Tests

The “full failsafe” nature of the Rx can be evaluated by manipulating the “A1” (1) and “B1” (4) input jumpers. In the default configuration, A1 and B1 float, but RA (measure at the “RB1(RA)” test point to the right of jumper (1)) remains high due to the failsafe “open” functionality. Installing jumpers “A1” (1) and “B1” (4) ef fectively shorts the two inputs together (i.e., V the Rx is also failsafe “shorted”. The combination of failsafe “open” and “shorted” yields a “full-failsafe” Rx.

To switch the Rx output state leave the “B1” (4) jumper installed, remove the “A1” (1) jumper, and install the A1 Rx bias jumper, “J10” (2). The “RXBIAS-VCC” (15) jumper now drives the A1 input voltage to V

=0). RA still remains high, indicating that

, which switches RA low.

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Application Note 1248

Removing the “RXBIAS-VCC” (15) jumper , and connecting a power supply between the “RXBIAS” banana jack and GND now sets the Rx differential input voltage, via “A1”, and varying this supply switches the Rx output state. For example, with the RXBIAS supply = 0V (V

=0V) the

output is high, and increasing RXBIAS to at least +200mV (V

= -200mV) switches RA low.

To disable the Rx output via the active high RXEN pin, ensure that the “RXEN1

” (10) jumper is in the “VH” position, and move jumper “(RXEN)” (11) to the “LOW” position. To disable the Rx output via the active low RXEN

pin, ensure that the “(RXEN)” jumper is in the “LOW” position, and move jumper “RXEN1

” to the “VH” position.

Return the “RXEN1” and “(RXEN)” jumpers to the “VH” position, remove the “RXBIAS” power supply and jumpers “J10” and “B1”, and reinstall the “RXBIAS-VCC” jumper.

Driver Tests

Tx DC output levels are independent of Tx speed setting. In the default configuration, the driver input, DY, is low, so the Tx noninverting output, Z1, is low, while the inverting output, Y1, is high. To switch the output states, simply move the “DZ1/DE1 (DY) (14) jumper to the “VH” position. In either state, note the exceptionally large differential voltage (V of ≈3.5V. To evaluate the double terminated V

(≈3.3V), install resistors R7 and R9, and configure the board for “external loopback”, as described previously (i.e., install jumpers (5) and (6)).

To disable the Tx output via the active high DEN pin, move the “(DEN)” (8) jumper from the “VH” to the “LOW” position.

When finished, return the “DZ1/DE1 (DY)” and “(DEN)” jumpers to the “LOW” and “VH” positions respectively, and remove the “external loopback” jumpers.

Internal Loopback

To configure the ISL41387 for internal loopback mode, simply move the “(ON)” (12) jumper to the “LOW” position, while ensuring that the “(DEN)” (8) and “(RXEN)” (11) jumpers are set to “VH”. Note that I

increases by ≈1.4mA,

due to the enabling of the loopback receivers. RA is now low due to the Tx outputs internally driving the Rx. You can repeat the previous Rx switching tests to confirm that the external Rx input pins now have no affect on RA.

The internal loopback receivers are not RS-485/422 compliant, so internal loopback can’t be used to create a half duplex transceiver.

Low Power SHDN

With the “(ON)” (12) jumper still in the “LOW” position, move the “(DEN)” (8) and “(RXEN)” (11) jumpers to the “LOW” position, while ensuring that the “RXEN1

” (10) jumper is set to “VH”. This setting places the ISL41387 into shutdown (SHDN), which disables the Tx and Rx outputs, and places

the IC in its lowest power mode. Note that I

drops to less

than 5µA. Return jumpers “(ON)”, “(DEN)”, and “(RXEN)” to the “VH”

position.

Basic RS-485 AC Evaluation

Remember that there aren’t any differential term resistors, so if they are desired they must be added at positions R7 for the Tx - and R9 for the Rx.

Receiver Tests

Before starting, ensure that the jumpers are back in the default positions. Note that the RS-485 Rx operates at high speed, regardless of the Tx speed selection.

Add jumper “B1” (4) to connect that input to GND, and add jumper “A1” (1) to engage the 50Ω term. Connect a generator to the “A1” BNC, and set it for a -1.5V to +1.5V swing. Monitoring test points “TP6” (input), and “RB1 (RA)” (output) with a scope allows the Rx prop delays and skews to be measured. If desired, you can load the Rx output with a 1kΩ resistor by adding jumper “J6” (not numbered), located below test point “RB1 (RA)”. This resistor terminates to the “VLOAD” banana jack (upper left hand corner), allowing the

)

resistor to be terminated to GND by shorting “VLOAD” to GND, or terminated to any voltage by connecting “VLOAD” to an external supply.

You can also measure the Rx enable/disable time to/from a low output state via the active high RXEN pin. From the previous jumper configuration, leave the “B1” and “J6” jumpers installed, remove the “A1” jumper, and install the A1 Rx bias jumper, “J10” (2). Connect the “VLOAD” jack to V

switch the “(RXEN)” (11) jumper to the low position to engage the 50Ω term, set the generator to swing from 0V to 3V, and move the generator to the “NC (RXEN)” BNC. Monitoring test points “TP12” (input), and “RB1 (RA)” (output) with a scope allows the Rx enable and disable times to be measured. To evaluate the Rx enable/disable time to/from a high output state, simply remove “J10”, and connect “VLOAD” to GND.

To evaluate the Rx enable/disable times using the active low RXEN

pin, repeat the previous test but leave the “(RXEN)”

jumper in the “LOW” position, move the “RXEN1

” (10) jumper to the “LOW” position to connect the 50Ω term, and connect the generator to the “RXEN1

” BNC.

Tx Speed Selection

Before performing any Tx switching tests, ensur e th at the jumpers are in their default positions, and then configure the “DZ/(SLEW)” (13) and “SPB” (9) jumpers for the desired Tx speed setting. Table 1 details the jumper settings for each of the speed options.

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Application Note 1248

TABLE 1. JUMPER SETTINGS FOR Tx SPEED SELECTION

DATA RATE J-(DZ/SLEW)

(13) J-SPB (9)

115kbps “LOW” “LOW”

460kbps “LOW” “VH”

20Mbps “VH” “LOW” or “VH”

Driver Tests

There are no driver loads on this board, so if loading is desired a differential load resistor, and/or differential load capacitor may be added at position “R7”. Alternatively, single ended loads (Y or Z to GND) may be added at positions “C4” and “C2”.

Ensure that the “DZ1/DE1 (DY)” (14) jumper is in the “LOW” position to engage the 50Ω term resistor, connect the generator to the “DZ1/DE1 (DY)” BNC, and set the swing for 0 to 3V. Monitoring test points “TP18” (input), and “TP5” and “TP2” (Y and Z outputs respectively) with a scope allows the Tx prop delays, skews, and transition times to be measured. To view the differential waveform, use the scope’s math function to generate “Z-Y”.

To measure the Tx output enable and disable times, start with the previous jumper configuration and move the “DEN” (8) jumper to the “LOW” position to engage its 50Ω term resistor. Connect the generator to the “NC (DEN)” BNC, and set the swing for 0 to 3V. Monitoring test points “TP9” (input), and “TP5” and “TP2” (Y and Z outputs respectively) with a scope allows the enable and disable times to be measured. Note that some form of termination resistor must be used to pull the disabled outputs to a known state; a differential termination resistor at “R7” is the easiest approach.

Evaluating Driver and Receiver Combined Performance

Performance through a cascaded Tx and Rx can easily be evaluated, utilizing the external loopback function, by installing jumpers “A1/Y1_LB (5) and “B1/Z1_LB (6). In this configuration, the Tx output lines connect to the corresponding Rx input lines, so the data driven on the Tx input (DY) appears at the Rx output (RA).

Installing resistors R7 and R9 allows evaluation of the performance with the Tx driving a double terminated load.

Interconnecting Driver and Receiver with a Cable

To evaluate the performance of the Tx and Rx interconnected by a cable, start with the default configuration, connect single wire of a twisted pair between test points “TP2” and “TP1”, and connect the other wire in the pair between “TP5” and “TP6”. Ensure that the “DZ1/DE1 (DY)” (14) jumper is in the “LOW” position to engage the 50Ω term resistor, connect the generator to the “DZ1/DE1 (DY)” BNC, and set the swing for 0 to 3V. Monitoring test points “TP18” (input), and test point “RB1(RA)” illustrates the overall input to output performance.

Installing resistors R7 and R9 allows evaluation of the performance with the Tx driving a double terminated cable.

Switching to RS-232 Mode

To set the board for RS-232 evaluation, start with the jumpers in the “default configuration”, and move jumper “A2 (485/232

)” (7) to the “LOW” position. If RS-485 termination resistors (“R7” or “R9”) were added, ensure that they have been removed. Note that the RS-232 data rate is fixed at 500kbps, so the “SPB” (9) jumper has no affect (connect it high to minimize SHDN I

), and that the

“SLEW” pin becomes the second driver input, DZ. Figure 1 illustrates the 41387 configuration in this mode.

5kΩ

(16)

GND

+5V

0.1μF C

0.1μF

C1+

C1-

C2+

C2-

329

DEN

485 / 232

FIGURE 1. DEFAULT RS-232 CONFIGURATION

15, 16

(17)

RXEN

V+

V-

VHIGH (VH )

0.1μF

RXEN 17

Basic RS-232 DC Evaluation

General Observations

Note that V+ and V- now pump up to approximately +6V and

-7V, respectively, and the charge pump operation increases I

to 3.8mA. Also note that RS-232 drivers and receivers

are inverting by definition. Before starting, ensure that resistors R7 and R9 are

removed, if they have been previously installed.

Receiver Tests

In the default configuration of Figure 1, RB (measure at the “RA1 (RB)” test point to the left of jumper (14)) and RA (measure at the “RB1(RA)” test point to the right of

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Application Note 1248

jumper (1)) are high due to the A1 and B1 5kΩ input resistors to GND.

To switch the Rx output states, install the A1 and B1 Rx bias jumpers, “J10” (2) and “J9” (3). The “RXBIAS-VCC” (15) jumper now drives the Rx input voltages to V

, which switches RA and RB low. Removing the “RXBIAS-VCC” jumper and connecting a power supply between the “RXBIAS” banana jack and GND, allows this supply to set the Rx input voltages, in case the user wants to evaluate the Rx switching points.

To disable the Rx outputs via the active high RXEN pin, remove “J10” (2) and “J9” (3), and switch the “(RXEN)” (11) jumper to the “LOW” position (make sure the “RXEN1

” (10) jumper is in the “VH” position). To disable the Rx outputs via the active low RXEN1

pin, move jumper “RXEN1” to the “VH” position (make sure the “(RXEN)” jumper is in the “LOW” position).

Return the “RXEN1

” and “(RXEN)” jumpers to the “VH” position, remove the “RXBIAS” power supply, and reinstall the “RXBIAS-VCC” (15) jumper.

Driver Tests

The RS-232 Tx outputs, Y and Z, are high (≈6.5V) and low (≈ -7V), respectively, in the default configuration. To switch the output states, simply switch the “DY1 (DZ/SLEW)” (13) and “DZ1/DE1 (DY)” (14) jumpers (note Rev. A label errors) to the opposite states. To evaluate the loaded driver output voltages, configure the port for “external loopback”, as described previously (i.e., install jumpers (5) and (6)). Each driver output is now loaded by an Rx input resistor (≈5kΩ), and the output voltages still exceed ±6.2V.

The driver outputs can be disabled by moving the “(DEN)” (8) jumper to the “LOW” position.

Remove the “external loopback” jumpers when finished, switch the “DY1(DZ/SLEW)” and “(DEN)” jumpers to the “VH” position, and move the “DZ1/DE1 (DY)” jumper back to the “LOW” position.

Internal Loopback

increases due to the

enabling of the loopback receivers. RA is now low due to Tx output Y feeding back to Rx A, while RB is high due to Z feeding back to Rx B. You can repeat the previous Rx switching tests to confirm th at the exter nal Rx input p ins now have no affect on RA nor RB.

Low Power SHDN

The ISLX1387 enter the SHDN mode when “(ON)” (12) = “LOW”, and the Tx and Rx are disabled (“(DEN)” (8) = “LOW”, “(RXEN)” (11) = “LOW”, and

“RXEN1

(10) = “VH”), and the already low supply current

drops to as low as 5µA. SHDN disables the Tx and Rx outputs, and disables the charge pumps, so V+ collapses to V

, and V- collapses to GND.

All but 5µA of SHDN ICC current is due to the on-chip SPB pull-up resistor (~20µA/resistor), so SHDN I

varies depending on the ISLX1387 configuration. To evaluate the lowest SHDN I

, ensure that the “SPB” (9) jumper is in the

“VH” position.

Single Tx and Single Transceiver Modes

RS-232 mode also offers the options of selecting a single Tx mode, or a single Tx/Rx pair mode. T o evaluate the single Tx mode, set the “(ON)” (12) and “(RXEN)” (11) jumpers “LOW” and “(DEN)” (8) and “RXEN1

” (10) jumpers to “VH”. To evaluate the single Tx/Rx mode, set the “(ON)” and “(DEN)” jumpers “LOW” and either the “RXEN1

” jumper to “LOW” or

the “(RXEN)” jumper to “VH”.

Basic AC Evaluation

Before starting, ensure that the jumpers are back in the default RS-232 positions. Note that the RS-232 data rate is fixed, so the speed select pins have no effect.

Receiver Tests

Add jumper “A1” (1) to engage the 50Ω term, connect a generator to the “A1” BNC, and set it for at least a 0V to 3V swing. Monitoring test points “TP6” (input), and “RB1(RA)” (output) with a scope allows the Rx prop delays and skews to be measured. If desired, you can load the Rx output with a 1kΩ resistor by adding jumper “J6” (not numbered), located below test point “RB1 (RA)”. This resistor terminates to the “VLOAD” banana jack (upper left hand corner), allowing the resistor to be terminated to GND by shorting “VLOAD” to GND, or terminated to any voltage by connecting “VLOAD” to an external supply.

To measure the Rx enable/disable time to/from a high output state via the active high RXEN pin, start from the previous jumper configuration, leave the “J6” jumper installed, and connect the “VLOAD” banana jack to GND. Remove the “A1” jumper (Rx input is pulled low by its on-chip pull-down), switch the “(RXEN)” (11) jumper to the low position to engage the 50Ω term, set the generator to swing from 0V to 3V, and move the generator to the “NC (RXEN)” BNC. Monitoring test points “TP12” (input), and “RB1 (RA)” (output) with a scope allows the Rx enable and disable times to be measured. To evaluate the Rx enable/disable time to/from a low output state, install the A1 Rx bias jumper, “J10” (2).

To evaluate the Rx enable/disable times using the active low RXEN

pin, repeat the previous test but leave the “(RXEN)” jumper in the “LOW” position, move the “RXEN1 jumper to the “LOW” position to connect the 50Ω term, and connect the generator to the “RXEN1

” BNC.

” (10)

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Application Note 1248

Driver Tests

Ensure that the “DZ1/DE1 (DY)” (14) jumper is in the “LOW” position to engage the 50Ω term resistor, connect the generator to the “DZ1/DE1 (DY)” BNC, and set the swing for 0 to 3V. Monitoring test points “TP18” (input) and “TP5” (output) with a scope, allows the Tx prop delays, skews, and transition times to be measured.

To measure the “loaded” driver performance, simply remove the “J10” (2) jumper, and connect the “A1/Y1_LB” (5) jumper , which connects an Rx input, including its 5kΩ pull-down, to the driver output.

To measure the Tx output enable/disable times to/from a high output state, start with the previous jumper configuration and move the “(DEN)” (8) jumper to the “LOW” position to engage its 50Ω term resistor. Connect the generator to the “NC (DEN)” BNC, and set the swing for 0 to 3V. Monitoring test points “TP9” (input), and “TP5” (output) with a scope allows the enable and disable times to be measured. Note that some form of output termination resistor must be used to pull the disabled output to a known state; installing the “A1/Y1_LB” jumper is the easiest solution.

Evaluating Driver and Receiver Combined Performance

Performance through a cascaded Tx and Rx can easily be evaluated, utilizing the external loopback function. Insure that the “A1/Y1_LB (5) jumper is installed, that the “(DEN)” (8) and “(RXEN)” (11) jumpers are set to the “VH” position, and that the “DZ1/DE1(DY)” (14) jumper is in the “LOW” position. Connect the generator to the “DZ1/DE1(DY)” BNC, and set the swing for 0 to 3V. Monitoring test points “TP18” (input), and “RB1 (RA)” (output) with a scope allows evaluation of the total Tx and Rx performance. In this configuration, the Tx output line connects to an Rx input line, so the data driven on the Tx input (DY) appears at the Rx output (RA).

Evaluating the Logic Supply (VL) Function

The ISL41387 includes a VL pin that powers the logic inputs (Tx inputs and control pins) and Rx outputs, regardless of protocol selection. These pins interface with “logic” devices such as UARTs, ASICs, and μcontrollers, and today most of these devices use power supplies significantly lower than 5V. Connecting the V device limits the ISL41387’s Rx output V reduces the Tx and control input switching points to values compatible with the logic device’s output levels. If the logic device is also powered by 5V, then the V shorted to the V

Removing jumper “V power supply to the “V evaluate this function. V to 1.65V, but the input switching points may not provide enough noise margin when V typical V

and VIL values for various VL settings so the user

pin to the power supply of the logic

pin should be

pin.

” (16), and connecting a new

CC-VL

” banana jack allows the user to

can be anywhere from VCC down

< 1.8V. Table 2 indicates

to VL, and

can ascertain whether or not a particular V

voltage meets

his needs.

TABLE 2. VIH AND VIL vs VL FOR VCC = 5V

(V) VIH (V) VIL (V)

1.65 0.79 0.50

1.8 0.82 0.60

2.0 0.87 0.69

2.5 0.99 0.86

3.3 1.19 1.05

To evaluate the V while monitoring a high Rx output. To evaluate the V

impact on Rx VOH, vary the VL voltage

effect

on input switching points, remove the “VL-VHIGH” (17) jumper, connect a new supply between the “VHIGH” and “GND” banana jacks, set the V

supply to the desired

voltage, move the jumper of the input to be tested to the “VH” position, and vary the “VHIGH” supply to determine the switching point.

Jumper Definitions

The jumpers used to evaluate the ISL41387 are:

J-A1 (1) - Connects A1 input to GND through a 50Ω resistor. J10 (2) - Connects A1 input to the RXBIAS jack. J9 (3) - Connects B1 input to the RXBIAS jack. J-B1 (4) - Connects B1 input to GND through a 50Ω resistor. A1/Y1_LB (5) - Loops output Y1 back to input A1. B1/Z1_LB (6) - Loops output Z1 back to input B1. J-A2(485/232) (7) - “LOW” sets the IC to RS-232 mode;

“VH” sets it to RS-485 mode. J-(DEN) (8) - “LOW” disables RS-232 or RS-485 Tx outputs;

“VH” enables all Tx outputs. J-SPB (9) - Used with “SLEW” to set the RS-485 Tx data

rate (see Table 1).

J-RXEN1

outputs; “VH” disables Rx outputs (iff J-(RXEN) = “LOW”). J-(RXEN) (11) - “LOW” disables all RS-232 or RS-485 Rx

outputs (iff J-RXEN1 J-(ON) (12) - “LOW” places IC in “special features” mode

(loopback, SHDN, etc.); “VH” sets IC for normal operation. J-DY1(DZ/SLEW) (13) - “LOW” sets the Z Tx input low in

RS-232 mode or selects the slew rate limited data rates in RS-485 mode; “VH” sets the Z Tx input high in RS-232 mode or selects the 20Mbps data rate in RS-485 mode.

J-DZ1/DE1(DY) (14) - “LOW” sets the Y Tx input low in RS-232 or RS-485 Modes; “VH” sets the Y Tx input high in either mode.

(10) - “LOW” enables all RS-232 or RS-485 Rx

= “VH”); “VH” enables Rx outputs.

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Application Note 1248

RXBIAS-VCC (15) - Connects VCC to the “RXBIAS” jack; if driving RXBIAS from a voltage other than V

, remove this

jumper. VCC-VL (16) - Connects V

from a voltage other than V

to the “VL” jack; if driving VL

, remove this jumper.

VL-VHIGH (17) - Connects VL to the “VHIGH” jack; if driving VHIGH from a voltage other than V

, remove this jumper.

PCB Layout Information

The dimensions for the QFN land pattern used on this board are shown in Figure 2.

FIGURE 2. QFN LAND PATTERN AND DIMENSIONS (in mm)

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Application Note 1248

ISL41387EVAL1Z

FIGURE 3. JUMPER LOCATOR DIAGRAM

Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without notice. Accordingly, the reader is cautioned to verify that the Application Note or Technical Brief is current before proceeding.

For information regarding Intersil Corporation and its products, see www.intersil.com

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Application Note 1248

TP1

J-B1

TP5

TP2

VLOAD

VHIGH

B1/Z1_LB

J-SEL1

R10

VHIGH

J-SEL2

VLOAD

R11

*B2/Z2_LB

TP7

Z2 (NC)

Y2 (NC)

TP3

B2 (NC)

TP8

* Labels swapped on Rev A board

RXBIAS

R13

RXBIAS

J11

VHIGH

R15

J-B2

TP6

A1/Y1_LB

R14

*A2/Y2_LB

RXBIAS

J12

J-A2 (485/232

VHIGH

R20

RXBIAS

V+

J10

J-A1

VLOAD

RXBIAS

VLOAD

C26 C27

RXBIAS

C24 C25

C15

P-VCC

GND

VCC

RXBIAS-VCC

C8 C11

C10

VCC-VL

39 38 37 36 35 34 33 32 31

NC NC NCC1- C1+ C2+ C2- V

NC V

V+

GND

GND V-

11 12 13 14 15 16 17 18 19 20

VHIGH

J-SPB

VHIGH

J-SPA (NC)

V-

VHIGH

J-RXEN1

TP4

A2 (485/232)

)

(to pin 27)

J-(SLEW)

TP20

DY1 (DZ/SLEW)

R1, 3, 4, 8, 12, 15-18, 20, 24-26, 28 = 49.9Ω

R5, 6, 10, 11 = 499Ω (NOT POPULATED) R7, 9 = 121Ω (NOT POPULATED) R13, 14 = 121Ω R19, 22, 23, 27 = 1kΩ

C1, 6-8,10-14, 16, 18-21, 23-26 = 0.1μF C2-5 = 0.1μF (NOT POPULATED) C9, 15, 17, 22, 27 = 10μF

P-GND

C22

C13

C12

J-RXEN

R16

VHIGH

VL-VHIGH

VHIGH

TP11

VHIGH

C14 C23

C16

C17

R18

J-RXEN2

RXEN1

RB1(RA)

J-LB (NC)

RA2(NC)

NC (RXEN)

TP12

VHIGH

RA1(RB)

TP18

VHIGH

J14

TP10

R17

J-(DEN)

J13

VHIGH

TP16

J-ON/OFF

TP19

TP21

R23

C20

TP17

RXEN2 (NC)

VHIGH

R12

R19

R22

J-DE1

VHIGH

J-DE2

VLOAD

J-(ON)

TP9

C18

C19

ON/OFF (NC)

R25

J-DY2

DZ2/DE2 (NC)

R28

R27

VHIGH

VLOAD

R24

DY2 (NC)

VLOAD

C21

RB2 (ON)

R26

NC (DEN)

DZ1/DE1 (DY)

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