ANALOG DEVICES DC2757A Monolithic Buck Boost DC DC Converter Instruction Manual

ANALOG DEVICES DC2757A Monolithic Buck Boost DC DC Converter

Product Information

Specifications:

• Input Voltage Range: 1.8V – 5.5V
• Output Voltage: 3.3V
• Switching Frequency: 500kHz – 4MHz (programmable)
• Output Current: 5A
• Efficiency: Refer to the datasheet for details

Product Usage Instructions

Quick Start Procedure:

1. Ensure all power supplies are off and use short twisted pair leads for power connections.
2. Set up the equipment as shown in Figure 1.
3. Follow the steps below:
4. Set PS1 to OFF, LOAD to OFF, JP1 (EN) to ON, JP2 (MODE) to FIXED FREQ, JP3 (SS) to INT SS, and JP4 (RT) to 2.2MHz.
5. Connect the power supply (PS1) as per Figure 1, optionally adding an ammeter for current measurements.
6. Gradually increase the voltage from PS1 until VIN reaches 4.5V.
7. Verify that VOUT is around 3.3V.
8. Connect a 5A load to VOUT as depicted in Figure 1 and optionally use an ammeter for current measurement.

FAQ:

Q: What is the input voltage range for the DC2757A demo board?

A: The DC2757A operates with an input voltage range of 1.8V to 5.5V.

Q: How can I change the switching frequency of the LT3154 in PWM mode?

A: The switching frequency can be adjusted between 500kHz to 4MHz by programming the RT resistor R4.

Q: What is the output voltage of the LT3154 on the demo board?

A: The output voltage is set to 3.3V on the demo board.

DESCRIPTION

Demonstration circuit 2757A is a 6A buck-boost DC/DC converter featuring the LT®3154, a low-noise, low-IQ monolithic buck-boost converter with a programmable soft-start.

The DC2757A demo board has four user-selectable oper-ating modes:

• An accurate programmable EN/UVLO pin is used to ENABLE the converter (JP1).
• BURST MODE© and External CLK/Fixed Frequency PWM (JP2).
• Programmable Soft-Start (JP3).
• Selectable (2.2MHz) and Adjustable Switching Frequency RT (500kHz to 4MHz) (JP4).
• The LT3154 uses average current mode control to simplify voltage loop compensation and provide good line and load transient response.
• The DC2757A operates with a 1.8V to 5.5V input voltage range. The demo board has been designed with the output voltage set to 3.3V. The LT3154 incorporates a proprietary low-noise switching algorithm that optimizes efficiency with input voltages above, below, or equal to the output voltage and ensures seamless transitions between operating modes.
• In PWM mode, the LT3154 can operate with a switching frequency between 500kHz to 4MHz by program-ming the RT resistor R4. It also has a selectable switching frequency (2.2MHz) to optimize small size with high-efficiency operation. The LT3154 can be synchronized to the External CLK provided RT is programmed 25%-50% below the synchronization frequency.
• The LT3154 has a Soft-Start feature and can be programmed with the soft-start capacitor C13 (EXT SS). It also has a selectable internal soft-start (INT SS) of 2.2ms.
• Figure 2 shows typical demo board efficiency. Figure 3 and Figure 4 show the load step response.
• The LT3154 data sheet has detailed information about the operation, specifications, and applications of the part. The data sheet should be read in conjunction with this Quick Start Guide.

Design files for this circuit board are available.

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

PERFORMANCE SUMMARY

Specifications are at TA = 25°C

Internal

| 3.2

2.2

| MHz
Output Voltage VOUT| R5 = 1MΩ R6 = 432kΩ| 3.3| V
Output Current IOUT| VIN > 3.3V| 5A|
Efficiency| | See Figure 2| %
Note: Demo board output current is a function of input voltage. Refer to the datasheet for more information.

QUICK START PROCEDURE

Using short twisted pair leads for any power connections and with all loads and power supplies off, See Figure 1 for the proper measurement and equipment setup. The power supply (PS1) should not be connected to the circuit until told to do so in the procedure below. When measuring the input or output voltage ripple, care must be taken to avoid a long ground lead on the oscilloscope probe. Measure the input or output voltage ripple by touching the probe tip directly across the VIN or VOUT and GND terminals, or by using an oscilloscope probe tip jack.

1. Jumper and PS1 settings to start:

   • PS1 = OFF
   • LOAD = OFF
   • JP1 (EN) = ON
   • JP2 (MODE) = FIXED FREQ
   • JP3 (SS) = INT SS
   • JP4 (RT) = 2.2MHz

2. With power OFF, connect the power supply (PS1) as shown in Figure 1. If accurate current measurements are desired (for efficiency calculations for example), connect an ammeter in series with the supply as shown. The ammeter is not required, however.

3. Turn on PS1 and slowly increase the voltage until the voltage at VIN is 4.5V.

4. 4. Verify VOUT is ~3.3V.
   5. Connect a 5A load to VOUT as shown in Figure 1 (0.66Ω for VOUT = 3.3V). Connect an ammeter if accurate current measurement or monitoring is desired.

5. VIN can now be varied between 1.8V and 5.5V. IOUT needs to be reduced for VIN < VOUT to ensure VOUT remains in regulation.

6. Load current (IOUT) can also be varied. The maximum IOUT is a function of VIN and the current limit. Consult the datasheet for more information on IOUT vs VIN. For VIN > VOUT, IOUT can be increased to 5A. For VIN < 3.3V, the maximum IOUT is reduced.
   NOTE: If VOUT drops out of regulation, check to be sure the maximum load has not been exceeded, or that VIN is not below the minimum value (1.8V).

7. For operation in BURST Mode, move Jumper JP2 to BURST. Refer to the datasheet for more information.

8. For the programmable switching frequency, move Jumper JP4 to RT (3.2MHz), else it will default to a switching frequency of 2.2MHz.

9. For the programmable Soft-Start feature, move JP3 to EXT SS, else it will have a default Soft-Start of approx. 2.2ms.

TEST RESULTS

PARTS LIST

ITEM| QTY| REFERENCE| PART DESCRIPTION| MANUFACTURER/PART NUMBER
---|---|---|---|---

Required Circuit Components

XGL4020-601MEC
9| 1| R1| RES., 499kΩ, 1%, 1/16W, 0402, AEC-Q200| NIC, NRC04F4993TRF
10| 2| R2, R5| RES., 1MΩ, 1%, 1/16W, 0402, AEC-Q200| STACKPOLE ELECTRONICS, INC., RMCF0402FT1M00
11| 1| R3| RES., 2MΩ, 5%, 1/16W, 0402| VISHAY, CRCW04022M00JNED
12| 1| R4| RES., 34kΩ, 1%, 1/10W, 0402, AEC-Q200| KOA SPEER, RK73H1ETTP3402F
13| 1| R6| RES., 432kΩ, 1%, 1/16W, 0402| VISHAY, CRCW0402432KFKED
14| 1| R7| RES., 49.9Ω, 1%, 1/16W, 0402| ROHM, MCR01MZPF49R9
15| 1| R9| RES., 34.8kΩ, 1%, 1/10W, 0402, AEC-Q200| KOA SPEER, RK73H1ETTP3482F
16| 1| U1| IC, 6A Low Noise, High Performance Buck-Boost DC/DC Converter| ANALOG DEVICES, LT3154AV#PBF

Additional Demo Board Circuit Components

1| 0| C2, C3, C10, C11| CAP., OPTION, 1206|
---|---|---|---|---
2| 0| C4| CAP., 220µF, ALUM. ELECT., 20V, 20%, THT RADIAL| NICHICON, PLV1D221MDL1TD
3| 0| C12| CAP., OPTION, 0402|
4| 0| LB1| LABEL SPEC, DEMO BOARD SERIAL NUMBER| BRADY, THT-96-717-10
5| 0| R8| RES., OPTION, 0402|

Hardware: For Demo Board Only

1| 7| E1-E7| TEST POINT, TURRET, 0.094″ MTG. HOLE, PCB 0.062″ THK| MILL-MAX, 2501-2-00-80-00-00-07-0
---|---|---|---|---
2| 4| E8-E11| CONN., BANANA JACK, FEMALE, THT, NON- INSULATED, SWAGE, 0.218″| KEYSTONE, 575-4
3| 4| JP1-JP4| CONN., HDR, MALE, 1×3, 2mm, VERT, ST, THT| WURTH ELEKTRONIK, 62000311121
4| 4| MP1-MP4| STANDOFF, NYLON, SNAP-ON, 0.25″ (6.4mm)| KEYSTONE, 8831
5| 4| XJP1-XJP4| CONN., SHUNT, FEMALE, 2-POS, 2mm| SAMTEC, 2SN-BK-G

SCHEMATIC DIAGRAM

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ESD Caution
ESD (electrostatic discharge) sensitive device. Charged devices and circuit boards can discharge without detection. Although this product features patented or proprietary protection circuitry, damage may occur on devices subjected to high-energy ESD. Therefore, proper ESD precautions should be taken to avoid performance degradation or loss of functionality.

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