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dc1788bfa

DEMO MANUAL DC1788B

NOTE: Handle the DC1788B-C by the edge of the board.

Power over Ethernet Input
1. Refer to Figure 4 to evaluate the DC1788B-C with a  

DC/DC converter. If a resistive load is used to evaluate the 

DC1788B-C, connect the load by hand between VOUT+ 

and VOUT– after the LED (D3) is lit. It is recommended 

to disconnect the resistive load before powering down 

the DC1788B-C, so at the next turn on the load is discon-

nected. If the load is not connected and disconnected 

by hand properly, the PD may not power on. Contact 

field applications engineers for further details.

2. Connect the output of the PSE to the RJ45 connector 

(J1) on the DC1788B-C board with a CAT5e or CAT6 

Ethernet cable.

3. After connection has been established, verify that the 

LED (D3) is lit. This indicates the PSE has successfully 

detected and powered the PD.

Auxiliary Supply Input
1. Refer to Figure 5 to evaluate the DC1788B-C with a  

DC/DC converter and an auxiliary DC power supply.

2. Connect the auxiliary supply to the AUX+ to AUX– in-

puts. Check to make sure the voltage polarity is correct 

before turning on the auxiliary power supply.

3. Turn on the auxiliary power supply and verify that the 

LED (D3) is lit. 

Figure 4. Setup Diagram for the DC1788B-C with a DC/DC Converter and a Type 1 PSE

Dc1788B-c quick start proceDure

Summary of Contents for DC1788B

Page 1: ...r logo are registered trademarks and LTPoE and Hot Swap are trademarks of Linear Technology Corporation All other trademarks are the property of their respective owners controller These include a power good indicator a power sourcing equipment PSE type indicator and support for an auxiliary power input The major difference from the previous generation PD controller is that the LT4275 drives an ext...

Page 2: ...it drives an external N channel MOSFET to ramp up the output voltage After a successful PD controller output turn on the LT4275 drives a power good indicator PWRGD and a PSE Type indicator T2P DC1788B A and DC1788B B only ThePWRGDindicatorsignalstheloadtostartdraw ing current and the T2P indicator signals the load the type of PSE powering the PD Classification Signaling The resistors at RCLS and R...

Page 3: ... IEEE 802 3af Type 1 PoE Logic High DC1788B B LTPoE Logic Low IEEE 802 3at Type 2 PoE Logic Low IEEE 802 3af Type 1 PoE Logic High DC1788B C Any PSE Not Supported Theory of Operation Auxiliary Supply Support The DC1788B B and DC1788B C versions support an auxiliary supply input The auxiliary supply input has pri ority over the PoE input When the PD controller detects a valid voltage from the auxil...

Page 4: ...s select shunt positions are at JP1 and JP2 ontheDC1788B Aboard Inthisconfiguration anyPSE will turn on this PD Choose a power level from Table 3 and select the corresponding shunt positions 3 Check the power delivery capability of the LTPoE PSE to ensure it can power the PD and the load Do not select a jumper position corresponding to a higher power level than the LTPoE PSE can provide Oth erwise...

Page 5: ...ield applications engineers for further details 2 Connect the output of the PSE to the RJ45 connector J1 on the DC1788B B board with a CAT5e or CAT6 Ethernet cable 3 After connection has been established verify that the LED D3 is lit This indicates the PSE has successfully detected and powered the PD Auxiliary Supply Input 1 Refer to Figure 3 to evaluate the DC1788B B with a DC DC converter and an...

Page 6: ...6 dc1788bfa DEMO MANUAL DC1788B DC1788B B quick Start Procedure Figure 3 Setup Diagram for the DC1788B B with a DC DC Converter a Microprocessor and an Auxiliary DC Power Supply ...

Page 7: ...eers for further details 2 Connect the output of the PSE to the RJ45 connector J1 on the DC1788B C board with a CAT5e or CAT6 Ethernet cable 3 After connection has been established verify that the LED D3 is lit This indicates the PSE has successfully detected and powered the PD Auxiliary Supply Input 1 Refer to Figure 5 to evaluate the DC1788B C with a DC DC converter and an auxiliary DC power sup...

Page 8: ...8 dc1788bfa DEMO MANUAL DC1788B DC1788B C quick Start Procedure Figure 5 Setup Diagram for the DC1788B C with a DC DC Converter and an Auxiliary DC Power Supply ...

Page 9: ...9 dc1788bfa DEMO MANUAL DC1788B quick Start Procedure Figure 6 DC1788B A Efficiency at Various PoE Load Currents without LED D3 Figure 7 Thermal Image DC1788B A with 90W Load Top View ...

Page 10: ...10 dc1788bfa DEMO MANUAL DC1788B quick Start Procedure Figure 8 Thermal Image DC1788B A with 90W Load Bottom View ...

Page 11: ...ip 3 6k 5 0402 VISHAY CRCW04023K60JNEA 16 4 RT1 RT4 Res Chip 75Ω 5 0603 VISHAY CRCW060375R0JNEA 17 2 U2 U3 Quad MOSFETs FDMQ8203 FAIRCHILD FDMQ8203 DC1788B A BOM 1 1 Q1 Trans FDMC86102 POWER33 FAIRCHILD FDMC86102 2 1 R10 Res Chip 0Ω 5 0603 VISHAY CRCW06030000Z0EA 3 1 R15 Res Chip 100k 5 0603 VISHAY CRCW0603100KJNEA 4 1 R31 Res Chip 10k 1 0805 VISHAY CRCW080510K0FKEA 5 2 RC1 RC6 Res Chip 140Ω 1 080...

Page 12: ...CHILD FDN8601 7 2 Q7 Q8 Trans MMBTA42 300V SOT23 FAIRCHILD MMBTA42 8 1 R9 Res Chip 82 5k 1 0603 VISHAY CRCW060382K5FKEA 9 1 R10 Res Chip 20k 1 0603 VISHAY CRCW060320KFKEA 10 2 R15 R22 Res Chip 100k 5 0603 VISHAY CRCW0603100KJNEA 11 1 R16 Res Chip 34 8Ω 1 0805 VISHAY CRCW080534R8FKEA 12 1 R32 Res Chip 10k 5 0805 VISHAY CRCW080510K0JNEA 13 1 R33 Res Chip 56k 5 0603 VISHAY CRCW080556K0JNEA 14 1 R42 R...

Page 13: ...Ω 1 0805 VISHAY CRCW0805140RFKEA 14 1 RC2 Res Chip 76 8Ω 1 0805 VISHAY CRCW080576R8FKEA 15 1 RC3 Res Chip 49 9Ω 1 0805 VISHAY CRCW080549R9FKEA 16 1 RMPS1 Res Chip 4 3k 5 2512 VISHAY CRCW25124K30JNEA 17 1 T1 XFMR Würth 749023015 WÜRTH 749023015 18 1 U1 IC LT4275CIDD DFN10DD LINEAR TECHNOLOGY LT4275CIDD Optional Circuit Components 1 0 C2 Cap OPT 0402 OPT 2 0 E3 TP Turret 0 094 Opt OPT 3 0 JP2 JP4 JP...

Page 14: ...Customer Use Only CUSTOMER NOTICE LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A CIRCUIT THAT MEETS CUSTOMER SUPPLIED SPECIFICATIONS HOWEVER IT REMAINS THE CUSTOMER S RESPONSIBILITY TO VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL APPLICATION COMPONENT SUBSTITUTION AND PRINTED CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT PERFORMANCE OR RELIABILITY CONTACT LINEAR TECHNOLOGY APPL...

Page 15: ...ICATIONS ENGINEERING FOR ASSISTANCE THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND SCHEMATIC SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS SCALE NONE www linear com 1 Wednesday February 06 2013 2 2 LTPOE POWERED DEVICE KAUNG H KAUNG H N A LT4275XIDD SIZE DATE IC NO REV SHEET OF TITLE APPROVALS PCB DES APP ENG TECHNOLOGY Fax 408 434 0507 Milpitas CA 95035 Phone 408 432 1900 1630 McCarthy Blvd...

Page 16: ...INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE EXCEPT TO THE EXTENT OF THIS INDEMNITY NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR ANY INDIRECT SPECIAL INCIDENTAL OR CONSEQUENTIAL DAMAGES The user assumes all responsibility and liability for proper and safe handling of the goods Further the user releases LTC from all claims arising from the handling or use of the...

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