Analog Devices DC3170A-A/DC3170A-B

General Description

The demonstration circuit DC3170A-A/-B features the LTC7883 and LTC7051 in a high current, high efficiency 4-phase step-down converter. The LTC7883 is a 4-channel, 4-phase, voltage mode step-down controller with a PSM interface. The LTC7051 is a SilentMOST™ smart power stage integrating high-speed drivers with low RDS(ON) MOSFETs. The DC3170A-A/-B is available in two assembly types:

• DC3170A-A: VOA0 = 0.75V/50A, VOA1 = 0.9V/50A, VOB0 = 1.0V/50A, VOB1 = 1.2V/50A
• DC3170A-B: VOUT = 1.0V/200A, 4-phase

The DC3170A-A/-B operates at a switching frequency of 500kHz with an input voltage range of 7V to 14V. Each LTC7051 is driven by a three-state PWM output of the LTC7883, and its current sense and temperature outputs are monitored by the LTC7883. The circuit does not require external serial bus communications, using pre-programmed settings from the LTC7883's non-volatile memory.

For full access to the LTC7883's power system management features, download LTpowerPlay® software and use the ADI's I2C/SMBus/PMBus dongle DC1613A. LTpowerPlay allows reconfiguration, NVM storage, and telemetry viewing (voltage, current, temperature, fault status). Refer to the LTpowerPlay Software GUI section for details.

The LTC7883 and LTC7051 data sheets provide comprehensive IC operation and application information and should be read in conjunction with this manual. Design files are available at www.analog.com.

Performance Summary (TA = 25°C)

DC3170A-A

Note: The upper end of the output voltage range is limited by the 2V voltage rating of the bulk output capacitors. The lower end is limited by the minimum on-time of the LTC7051, the input voltage, and the switching frequency.

DC3170A-B

Note: The upper end of the output voltage range is limited by the 2V voltage rating of the bulk output capacitors. The lower end is limited by the minimum on-time of the LTC7051, the input voltage, and the switching frequency.

Quick Start Procedure

The evaluation setup is straightforward. Refer to Figure 1 (DC3170A-A) or Figure 2 (DC3170A-B) for setup diagrams.

1. With power off, connect the input supply, load, and meters. Preset the load to 0A and VIN supply to 0V.
2. Place the switches for RUNA0, RUNA1, RUNB0, and RUNB1 in the ON position.
3. Place the VCC RUN and VDRIVE RUN jumpers in the ON position.
4. Set the input voltage to 12V.
5. Check the output voltages; each rail should be within ±0.5% of its nominal value.
6. Apply the full load and recheck VOUT.
7. Adjust input voltage and load current to desired levels, observing regulation, output ripple, load step response, and efficiency.

Notes:

• Do not hot plug VIN to avoid transients that could damage the board.
• Ensure the electronic load is off before turning off the VIN supply to prevent output voltage from dropping below ground.

Measurement and Performance

Measurement Setup: Figures 1 and 2 illustrate the proper measurement equipment setup for the DC3170A-A and DC3170A-B, respectively. Figure 3 shows how to interface the board to a PC using the DC1613A dongle. Figure 4 demonstrates the proper method for measuring output voltage or input voltage ripple.

Measuring Efficiency: To measure efficiency, disable VCC and VDRIVE bias supplies by placing corresponding jumpers in the OFF position. Disconnect these supplies by removing jumpers at R139 and R143. Connect an external 5V bias supply to the VCC and VDRIVE turrets, including this power in measurements. For the DC3710A-A, disable unused rails via their RUN switches. Monitor VOUT and VIN at local ceramic COUT and CIN capacitors (see table in original document for specific locations).

Air Flow Requirements and Overtemperature Protection: The board can operate at full load with an airflow of 250 LFM or more. The LTC7883 monitors LTC7051 temperatures via the TDIO pin. Overtemperature fault thresholds are configured in the LTC7883's NVM: Warning threshold = 90°C, Shutdown threshold = 110°C. The system supports continuous restart attempts and direct VBE sensing.

Output Voltage and Input Voltage Ripple Measurements: Connect oscilloscopes to VOUT BNC connectors (labeled VOUTA0, VOUTA1, VOUTB0, VOUTB1 for DC3170A-A; VOUTA1 for DC3170A-B) using coaxial cables. These monitor voltage across specific output capacitors. Use 50Ω coupling on the oscilloscope to prevent noise. For measurements at other locations or VIN, use short, stiff leads and ensure the probe's ground ring contacts the negative terminal.

Dynamic Load Circuits: The DC3170A includes two dynamic load circuits (A and B) using MOSFETs (PSMN1R5-30BLE) and sense resistors. Circuit A connects to VOUTA0 or VOUTA1, and Circuit B to VOUTB0 or VOUTB1, depending on jumper settings. To apply a load step, follow the setup diagrams and connect a pulse generator to the respective PULSE GEN inputs. Preset the pulse generator amplitude to 0.0V and duty cycle to ≤2% at a frequency of 10Hz or faster. Monitor VOUT and ISTEP using oscilloscope BNC connectors (ISTEPA/ISTEPB) with 50Ω coupling.

Paralleling Outputs: Optional jumpers allow connecting phases for 4-phase output (DC3170A-B) or other configurations (2+1+1, 2+2, 3+1). Refer to the datasheet for details.

Interfacing to other PSM demo boards: The DC3170A can connect to other demo boards via connectors J11 and J12 for simultaneous monitoring and control.

LTpowerPlay Software GUI: LTpowerPlay is a Windows-based development environment for ADI power management ICs and demo boards. It supports offline configuration and provides diagnostic/debug features. It communicates via the DC1613A USB-to-SMBus controller. The software includes an automatic update feature. A Quick Start Procedure is provided, involving downloading/installing LTpowerPlay, connecting the board, launching the GUI, and navigating the system tree. Users can read RAM to PC (R icon), change output voltages via the Voltage tab (VOUT_COMMAND), write to RAM (W icon), save to NVM (RAM to NVM button), and save project files.

Typical Performance Characteristics:

• Efficiency: Figures 5 and 6 show efficiency and power loss curves for DC3170A-A and DC3170A-B under various input voltages and load currents. Conditions include disabling certain supplies and using an external 5V bias.
• Thermal Image: Figure 7 shows a thermal image of the DC3170A-B under full load (200A), identifying the hottest spot on LTC7051 at U3 (phase B0). Conditions: VIN = 12V, Airflow = 250 LFM, Ambient Temp = 23°C.
• Current Sharing: Figure 8 illustrates current sharing accuracy for the DC3170A-B under VIN = 12V, with conditions R_SNS = 49.9Ω, IOUT_CAL_GAIN = 0.499mΩ, MFR_IOUT_CAL_GAIN_TC = 0ppm/°C.
• Load Step Response: Figures 9-13 show load step responses (e.g., 25A to 50A to 25A, 100A to 200A to 100A) for various output rails (VOUTA0, VOUTA1, VOUTB0, VOUTB1) under specified conditions (VIN, FSW, L, COUT).
• Temperature Readback: Table 1 compares LTC7051 readback temperature versus measured temperature for the DC3170A-B under different conditions, highlighting calibration parameters.

Bill of Materials Summary: The Bill of Materials lists a comprehensive set of components required for the evaluation boards. This includes various capacitors (e.g., 330pF, 680pF, 10µF, 100µF, 560µF) from manufacturers like Murata, AVX, TDK, and Panasonic; resistors (e.g., 1kΩ, 10kΩ, 0Ω) from Vishay, Yageo, and others; diodes; MOSFETs; ICs (LTC7051, LTC7883, ADR1581A); connectors; test points; and other passive components. Specific part numbers and quantities are detailed in the original document.

Schematics: The document includes detailed schematics for the DC3170A-A and DC3170A-B, illustrating the circuit design, component interconnections, and power delivery paths for the LTC7883 and LTC7051 controllers and associated power stages.