ANALOG DEVICES LTM4638 Step Down µModule Regulator User Manual

ANALOG DEVICES LTM4638 Step Down µModule Regulator

Specifications

• Input Voltage Range: 3.1V – 20V
• Output Voltage: 0.98V – 5.1V
• Maximum Continuous Output Current: 15A
• Default Operating Frequency: 600kHz
• Efficiency: 85.3%

DESCRIPTION

Demonstration circuit 2665B-B features the LTM®4638 µModule® regulator, a high performance, high effi-ciency step-down regulator. The LTM4638 is a complete DC/DC point-of-load regulator in a thermally enhanced 6.25mm × 6.25mm × 5.02mm BGA package. The LTM4638 has an operating input voltage range of 3.1V to 20V and provides an output current up to 15A. The output voltage is programmable from 0.6V to 5.5V and can be remotely sensed. The stacked inductor design improves thermal dissipation and significantly reduces the package area. Output voltage tracking is available through the TRACK/ SS pin for supply rail sequencing. External clock synchronization is available through the SYNC/MODE pin. For high efficiency at low load currents, select discon-tinuous current mode (DCM) operation using the MODE jumper (JP7) in less noise sensitive applications. Refer to the LTM4638 data sheet in conjunction with this demo manual for working on or modifying the DC2665B-B.

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

1.47

2.45

3.23

4.9

| 1.0

1.5

2.5

3.3

5.0

| 1.02

1.53

2.55

3.37

5.1

| V V V V V
Maximum Continuous Output Current| Derating Is Necessary for Certain Operating Conditions (See Data Sheet for Details)| 15| A
Default Operating Frequency| | 600| kHz
Efficiency| VIN = 12V, VOUT = 1V, IOUT = 15A| 85.3| %

QUICK START PROCEDURE

Demonstration circuit 2665B-B is an easy way to evaluate the performance of the LTM4638EY. Refer to Figure 1 for test setup connections and use the following procedure.

• With the power off, place the jumpers in the following

• Before connecting the input supply, load, and meters, preset the input voltage supply between 3.1V and 20V. Preset the load current to 0A.
• With the power off, connect the load, input voltage supply and meters as shown in Figure 1.
• Turn on the input power supply. The output voltage meters for each phase display the ±1.2% programmed output voltage .
•  Once the proper output voltage is established, adjust the load current in the 0A to 15A range and observe the load regulation, efficiency, and other parameters. Measure the output voltage ripple across the furthest output cap with a BNC cable and oscilloscope from J2.
• Place the MODE pin jumper (JP7) in the DCM position to observe increased light load efficiency.
• For optional load transient testing, an onboard transient circuit is provided to measure transient response. Place a positive pulse signal between the IO_STEP_CLK (E10) pin and GND pin. The pulse amplitude sets the load step current amplitude. Keep the pulse width short (<1ms) and the pulse duty cycle low (<15%) to limit the thermal stress on the load transient circuit. Monitor the load step with a BNC connected to J1 (5mV/A).

QUICK START PROCEDURE

NOTES

• To achieve the minimum output ripple voltage, optimize the operation frequency at different input and output voltages. Suggested operation frequencies at different voltages are shown in Table Adjust the operation frequency by changing the value of RfSET (R5). Refer to the LTM4638 data sheet for detailed calculation of RfSET (R5).
  Table 1. Suggested Operation Frequencies

| 3.3V IN| 5V IN| 12V IN
---|---|---|---
V OUT (V)| 1| 1.2| 1.5| 1.8| 2.5| 1| 1.2| 1.5| 1.8| 2.5| 3.3| 1| 1.2| 1.5| 1.8| 2.5| 3.3| 5
f SW (kHz)| 500| 500| 500| 500| 500| 600| 600| 600| 800| 800| 800| 600| 600| 800| 800| 1000| 1000| 1500

• For applications that require small output voltage ripple, add shunt-through three-terminal capacitors on the output at C41 and C42.

QUICK START PROCEDURE

Figure 2. Measured Supply, CCM Efficiency vs Load Current

Figure 3. Measured Thermal Capture at 12VIN, IOUT = 15A at 25°C Ambient with No Airflow

QUICK START PROCEDURE

Figure 4. Load Transient (7.5A to 11.25A) Response Waveform at 12VIN

Figure 5. Tested VOUT AC Ripple at 12VIN, IOUT = 15A , VOUT Ripple Is Tested Across C12

PARTS LIST

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

Required Circuit Components

GRM31CR60J227ME11L
5| 1| C7| CAP., 0.1μF, X7R, 25V, 10%, 0603| AVX, 06033C104KAT2A
6| 1| C8| CAP., 100pF, X7R, 25V, 5%, 0603| AVX, 06033C101JAT2A
7| 1| C10| CAP., 220μF, ALUM HYB, 35V, 20%| SUN ELECTRONIC, 35HVH220M
8| 1| C18| CAP., 1μF, X7R, 10V, 20%, 0603| AVX, 0603ZC105MAT2A
9| 1| C29| CAP., 0.022μF, X7R, 50V, 10%, 0603| KEMET, C0603C223K5RAC7867
10| 1| C34| CAP., 1μF, X7R, 6.3V, 10%, 0402| MURATA, GRM155R70J105KA12D
ITEM| QTY| REFERENCE| PART DESCRIPTION| MANUFACTURER/PART NUMBER
---|---|---|---|---
11| 1| R3| RES., 10k, 1%, 1/10W, 0603| VISHAY, CRCW060310K0FKEAC
12| 1| R4| RES., 90.9k, 0.5%, 1/10W, 0603| SUSUMU, RG1608P-9092-D-T5
13| 1| R6| RES., 40.2k, 0.5%, 1/10W, 0603| SUSUMU, RG1608P-4022-D-T5
14| 1| R14| RES., 13.3k, 0.5%, 1/10W, 0603| SUSUMU, RG1608P-1332-D-T5
15| 1| R15| RES., 19.1k, 0.5%, 1/10W, 0603| SUSUMU, RG1608P-1912-D-T5
16| 1| R24| RES., 8.25k, 0.5% 1/10W 0603| SUSUMU, RG1608P-8251-D-T5
17| 2| R8, R16| RES., 100k, 1%, 1/10W, 0603| STACKPOLE ELECTRONICS, RMCF0603FG100K
18| 2| R9, R10| RES., 0Ω,5%, 1/16W, 0402| ROHM, SFR01MZPJ000
19| 1| R17| RES., 0Ω, 1/10W, JUMPER, 0603| YAGEO, RC0603FR-070RL
20| 1| R7| RES., 150k, 5%, 1/10W, 0603| YAGEO, RC0603JR-07150KL
21| 1| Q1| XSTR, MOSFET, N-CH, 40V, TO-252 (DPAK)| VISHAY, SUD50N04-8M8P-4GE3
22| 1| RS2| RES., SENSE, 0.005Ω, 1%, 1W, 2512| VISHAY, WSL25125L000FEA
23| 1| U1| IC, 20V, 15A STEP-DOWN μModule REG| ANALOG DEVICES, INC. LTM4638EY#PBF

Additional Demo Board Circuit Components

Hardware: For Demo Board Only

38| 10| E1, E3, E5, E6, E8-E12, E14| TESTPOINT, TURRET 0.064″| MILL-MAX, 2308-2-00-80-00-00-07-0
---|---|---|---|---
39| 4| E2, E4, E7, E13| JACK, BANANA| KEYSTONE, 575-4
40| 2| J1, J2| CONN, BNC, 5 PINS| AMPHENOL RF, 112404
41| 5| JP1-JP6| HEADER, 1×2, 2mm| SULLINS, NRPN021PAEN-RC
42| 1| JP7| HEADER, 2×3, 2mm| SULLINS, NRPN032PAEN-RC
43| 1| JP8| HEADER, 1×3, 2mm| SAMTEC, TMM-103-02-L-S
44| 4| MP1-MP4| STAND-OFF, NYLON 0.5″| KEYSTONE, 8833 (SNAP ON)
45| 3| XJP1, XJP7, XJP8| SHUNT, 2mm| SAMTEC, 2SN-BK-G

SCHEMATIC DIAGRAM

REVISION HISTORY

DEMO BOARD REV| DEMO MANUAL REV| DATE| DESCRIPTION| PAGE NUMBER
---|---|---|---|---
DC2665A-B| 0| 02/19| Initial Release.| —
DC2665B-B| 0| 12/22| DC2665B-B replaces DC2665A-B for low HF VOUT ripple.| —

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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