ANALOG DEVICES LTM4702EY Step Down Module Regulator Low Noise Reference Instruction Manual

ANALOG DEVICES LTM4702EY Step Down Module Regulator Low Noise Reference Instruction Manual

DESCRIPTION

Evaluation board EVAL-LTM4702-AZ is a step-down DC/DC switching converter featuring the LTM®4702 μModule® regulator. The evaluation board is designed to deliver 8A maximum output current from a 4V to 16V input. The LTM4702 employs Silent Switcher® architecture with internal hot loop bypass capacitors to achieve both low EMI and high efficiency. The LTM4702 contains a current mode regulator IC, power inductor, and a modest amount of input and output capacitance. A single resistor (R3) sets the output voltage, providing unity gain operation over the output range, resulting in virtually constant output noise independent of output voltage.

The EVAL-LTM4702-AZ evaluation board default switching frequency is 800kHz. An external resistor is placed from RT pin to GND (R7) to set the switching frequency.

SYNC pin programs three different operating modes (JP1 jumper): select PULSE for pulse-skipping mode with improved efficiency at light loads; select FCM for forced continuous mode operation where fixed frequency operation is more critical than low current efficiency and where the lowest output ripple is desired; select SYNC to synchronize to an external clock signal.

The RUN terminal can be used to set the LTM4702 in shutdown mode. The power good output (PG) will be low when the output voltage is outside of the ±7.5% regulation window. When the power good feature is used, set the PGSET resistor (R1) value according to the regulator output voltage.

The LTM4702 data sheet gives a complete description of the operation and application information. The data sheet must be read in conjunction with this evaluation board.
Design files for this circuit board are available.

BOARD PHOTO

Part marking is either ink mark or laser mark

PERFORMANCE SUMMARY

Specifications are at TA = 25°C

QUICK START PROCEDURE

Evaluation board EVAL-LTM4702-AZ is easy to set up to evaluate the performance of the LTM4702. See Figure 1 for the proper measurement equipment setup and follow the procedure below.

1. With power off, connect the input power supply to VIN (4V to 16V) and GND (input return).

2. Connect the 1V output load between VOUT and GND (Initial load: no load).

3. Connect the DVMs to the input and output. Set default jumper position:
   JP1: FCM ON
   JP2: 120 PS ON

4. Turn on the input power supply and check for the proper output voltage. VOUT should be 1V ±2%.

5. Once the proper output voltage is established, adjust the load within the operating range and observe the output voltage regulation, efficiency, and other parameters.

NOTE: When measuring the output or input voltage ripple, do not use the long ground lead on the oscilloscope probe. See Figure 2 for the proper scope probe technique. Short, stiff leads may be soldered to the (+) and (–) terminals of an output capacitor. The probe’s ground ring needs to touch the (–) lead, and the probe tip needs to touch the (+) lead.

TYPICAL PERFORMANCE CHARACTERISTICS

Figure 1. Proper Measurement Equipment Setup

Figure 2. Measuring Output Ripple Voltage

TEST RESULTS

Figure 3. Efficiency vs Load Current, VIN = 12V

Figure 4. Output Voltage Ripple (12VIN, 1V, 8A Output)

Figure 5. Load Step Transient Test (VIN = 12V, VOUT = 1V)

Figure 6. Thermal Image, VIN = 12V, 1V, 8A Output (No Heat Sink, No Forced Airflow)

PARTS LIST

ITEM| QTY| REFERENCE| PART   DESCRIPTION| MANUFACTURER/PART NUMBER
---|---|---|---|---
1| 1| C1| CAP., ALUM POLY HYBRID, 100μF, 25V, 20%, 6.3mm × 7.7mm, AEC-Q200| PANASONIC, EEHZC1E101XP
2| 1| C10| CAP. CER, 1μF, 25V, 10%, X7R, 0603, AEC-Q200| TDK, CGA3E1X7R1E105K080AC
3| 2| C11, C12| CAP. CER, 22μF, 25V, 10%, X7R, 1210| MURATA, GRM32ER71E226KE15L
4| 4| C13, C14, C15, C16| CAP. CER, 10μF, 6.3V, 20%, X7S, 0603| TDK, C1608X7S0J106M080AC
5| 2| C6, C17| CAP. CER, 100μF, 10V, 20%, X5R, 1206, LOW ESR| TDK, C3216X5R1A107M160AC
6| 3| C18, C23, C24| CAP. CER, 0.1μF, 25V, 10%, X7R, 0603| SAMSUNG, CL10B104KA8NNNC
7| 1| C19| CAP. CER, 2200pF, 16V, 10%, X7R, 0603| VISHAY, VJ0603Y222KXJCW1BC
8| 1| C2| CAP. CER, 22μF, 25V, 20%, X5R, 0805, AEC-Q200| MURATA, GRT21BR61E226ME13L
9| 2| C21, C22| CAP FEEDTHRU, 4.7μF, 10V, 20%, 0805, 3-TERMINAL| MURATA, NFM21PC475B1A3D
10| 3| C3, C4, C5| CAP. CER, 2.2μF, 25V, 10%, X5R, 0603| MURATAGRM188R61E225KA12D
11| 1| C9| CAP. CER, 1μF, 10V, 10%, X7R, 0805| AVX, 0805ZC105KAT2A
12| 1| FB1| IND., CHIP FERRITE BEAD, 0.015Ω, DCR, 5.1A| WURTH ELEKTRONIK, 74279228600
13| 1| L1| IND., POWER SHIELDED WIREWOUND, 0.0073Ω, DCR, 9.5A| WURTH ELEKTRONIK, 744373240022
14| 1| R1| RES., SMD, 49.9k, 1%, 1/10W, 0603, AEC-Q200| PANASONIC, ERJ- 3EKF4992V
15| 1| R10| RES., SMD, 0Ω, 1%, 1/4W, 1206| VISHAYWSL, 120600000ZEA9
16| 1| R12| RES., 1.2k, 1%, 1/10W, 0603, AEC-Q200| VISHAY, CRCW06031K20FKEA
17| 1| R13| RES., SMD, 0Ω, JUMPER, 1/10W, 0603, AEC-Q200,PRECISION POWER| VISHAY, CRCW06030000Z0EA
18| 2| R2, R5| RES., SMD, 100k, 1%, 1/10W, 0603, AEC-Q200| PANASONIC, ERJ- 3EKF1003V
19| 1| R3| RES., SMD, 10k 1%, 1/10W, 0603, AEC-Q200| PANASONIC, ERJ-3EKF1002V
20| 1| R4| RES., SMD, 1Ω, 1%, 1/10W, 0603| YAGEO, RC0603FR-071RL
21| 1| R7| RES., 137k, 1%, 1/10W, 0603, AEC-Q200| VISHAY, CRCW0603137KFKEA
22| 1| U1| IC-ADI, 18VIN, 8A, Silent Switcher, μModule REGULATOR| ANALOG DEVICES, LTM4702EY#PBF
18| 0| C7, C8, C20, C25| OPTIONAL CAPACITOR|
19| 0| R6, R8, R9, R11| OPTIONAL RESISTOR|
20| 0| L2| OPTIONAL INDUCTOR|
24| 2| J1, J2| CONN., PCB, SMA, FEMALE JACK, RCP, 50Ω| MOLEX, 732511350
26| 2| JP1, JP2| CONN., HDR, MALE, 2 × 3, 2mm, VERT, ST, THT| WURTH ELEKTRONIK, 62000621121
27| 4| | STANDOFF, BRD, SPT, SNAP-FIT, 9.53mm LENGTH, EVAL BOARD MTG| KEYSTONE, 8832
28| 2| | CONN., SHUNT, FEMALE, 2-POS, 2mm| KEYSTONE, 8831
29| 1| PCBs| FAB PRINTED CIRCUIT BOARD| WURTH ELEKTRONIK, 702931000

SCHEMATIC DIAGRAM

REVISION HISTORY

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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