MAXREFDES179

• MAXREFDES179 reference design board package (Figure 2)
  • MAXREFDES179 reference design board and Micro-B USB cable
  • MAXREFDES179 Battery Power and MAXREFDES179 Battery Fuel Gauge software (GUI)
• Oscilloscope
• Battery simulator
• Voltage and current multimeters
• USB-C PD power adapter (USB compliant) and USB-C to on-the-go (OTG) cable
• PC with Windows 10 operating system

The reference design board is fully assembled and tested. Follow the steps to verify the board operation:

1. Identify the connections and test points (Figure 1). Confirm all the shunts and jumpers are at their default positions (Table 1).
2. Install the MAXREFDES179 Battery Power and MAXREFDES179 Battery Fuel Gauge software (GUI) on the PC.
3. Connect the Micro-B USB cable from the PC to the MAXREFDES179 reference design board. The Light-Emitting Diodes (LEDs) light up. Figure 3 shows the driver is installed properly.
4. Set up the test circuit (Figure 4). Preset the battery simulator to 7.4V and current limit to 100mA.
5. Toggle SW2 to wake the MAX17320 fuel gauge (needed only to power cycle the board).
6. Ensure the battery sourcing current is low (<100mA). Then only increase the current limit to 5A.
7. Start the MAXREFDES179 Battery Power GUI and click Connect. A pop-up message indicates the successful connection (Figure 5). Proceed with Read and Close.
8. Start the MAXREFDES179 Battery Fuel Gauge GUI. It automatically connects to the reference design.
9. Read the status of the USBC, charger, 2S to 1S battery voltage conversion, and fuel gauge.


1. MAX77958 USBC tab → Interrupts, Status, Command (Figure 6 and Figure 7).
2. MAX77960/MAX77961 Charger tab → Interrupts/Status, Configurations (Figure 8 and Figure 9).
3. MAX77932 tab → Status, Configurations (Figure 10 and Figure 11).
4. MAXREFDES179 Battery Fuel Gauge → ModelGauge m5, protector, graphs, etc. (Figure 12)


10. The reference design completes its initialization. The V_BUS, V_SYS, and I²C pull up. The CC pin waveforms can be monitored using the oscilloscope (Figure 13).

Detailed Description of the Hardware and Software

Software (GUI and Drivers)

• Contact the respective Maxim representative to download the GUI.
• The Future Technology Devices International (FTDI) drivers installation guide is available on the FTDI webpage.

Switched-Capacitor Converter, Fuel Gauge, Charger, and USB-C Measurement Points

The reference design board has various test points to evaluate the performances of the switched-capacitor converter (MAX77932), fuel gauge (MAX17320), buck-boost charger (MAX77960/MAX77961), and USB-C PD (MAX77958). Table 2, Test points, summarizes the recommended test points.

Demo 1: Switched-Capacitor Converter (MAX77932) Power Up/Down

Figure 14 shows the MAXREFDES179 reference design board setup to power-up/down the MAX77932.

• Enable and disable MAX77932 by the EN pin (Figure 15).
• Enable and disable MAX77932 by the I2C configuration (Figure 16).
• Enable MAX77932 by the EN pin and disable MAX77932 by the VIO signal (Figure 17).

Figure 17. Enable MAX77932 by the EN pin and disable MAX77932 by the V_IO signal.

Demo 2: Power Adapter is Connected When in Battery Mode

Figure 18 shows that the MAXREFDES179 reference design board setup supports autonegotiate for the highest PD power profile. Any USB-C PD adapter between 15W to 100W can be plugged in. The default highest PD power profile is 45W (15V/3A). Follow the steps to read the status:

• Figure 19 shows the VBUS waveform when the power adapter is connected.
• Read the USBC Status and observe the VBUS analog-to-digital converter (ADC) changes (Figure 20).
• Read the current SrcCap, charger configuration, and status (Figure 21 and Figure 22).
• Figure 23 shows the battery charging voltage and current.

Demo 3: Manual Negotiation for a Different PD Profile

The MAXREFDES179 reference design board is user-programmable to negotiate for a different PD profile. Follow the steps to program to the other PD profile:

• Battery Mode Setup - Plug in the USB-C PD power adapter (USB compliant) and connect the GUI (Figure 24).
• Go to the Command tab → Select Current SrcCap (0x30) and click Write to read the selected PDO and current source capabilities of the far-end device. For example, the negotiated highest PD power profile is 15V, 3A (Figure 25). Fill the SrcCap request and click Write to request for a different source capability. For example, request for PDO2 (9V, 3A) as the new PD power profile (Figure 26).
• The V_BUS changes from 15V to 9V (Figure 27).
• Read the newly selected PDO in the Current SrcCap (0x30) and USB status (Figure 28).

Demo 4: Sink (PPS) with GUI Control

The MAXREFDES179 reference design board is user-programmable to negotiate for a different PD profile. Follow the steps to program to the other PD profile:

1. Battery Mode Setup - Insert a 25W USB-C PD power adapter (PPS) and connect the GUI (Figure 29).
2. The AP has full control to achieve the best battery-charging efficiency by optimizing (increase/decrease) the VBUS voltage and current level.
3. MAXREFDES179 Battery Power GUI → Tools → Run Scripts → Select Scripts PPS_5V_to_11V_to_5V_2.25A → Execute. The scripts demonstrate that the PPS function is enabled and request a new APDO
4. (+500mV per second) from 5V to 11V. The scripts request a new APDO (-500mV per second) from 11V to 5V once the VBUS reaches 11V (Figure 30).

Demo 5: OTG Mode

The MAXREFDES179 reference design board supports the OTG mode autonomously. Follow the steps to read the OTG status:

1. OTG mode setup - Ensure the battery simulator is connected to the BATTP and BATTN pins. The GUI reads the register status. Plug in the OTG cable/device (Figure 31).
2. The V_BUS is enabled during the OTG mode (Figure 32).
3. Read the USBC Status and observe the V_BUS ADC (Figure 33).
4. Read the charger configuration (Figure 34 and Figure 35).

Demo 6: Initiate the Power Role Swap/Data Role Swap/V_CONN Swap

The MAXREFDES179 reference design board is user-programmable to initiate the power role swap, data role swap, and V_CONN swap. Connect to another MAXREFDES179 reference design board and follow the steps to initiate the power role swap:

1. Setup for the power role swap/data role swap/V_CONN swap (Figure 36).
2. Go to the Command tab and select Send Swap Request (0x37). Select 0x2 = Power Role in the drop down and click Write (Figure 37).
3. The power role swap request is accepted (Figure 38).
4. V_BUS transitions from the Source to Sink (Figure 39).
5. USB-C status after the power role swap is successful (Figure 40).

Follow the steps to initiate the data role swap:

• Go to the Command tab → Select Send Swap Request (0x37). Select 0x1 = Data Role in the drop down and click Write. The data role swap request is accepted (Figure 41).
• USB-C status after the data role swap is successful (Figure 42).

Follow the steps to initiate the V_CONN swap:

• Go to the Command tab → Select Send Swap Request (0x37). Select 0x3 = V_CONN in the drop down and click Write. The V_CONN swap request is accepted (Figure 43).
• V_CONN transitions from on to off (Figure 44).
• USB-C status after the V_CONN swap is successful (Figure 45).

Demo 7: Dead-Battery Bootup

The MAXREFDES179 reference design board supports the dead-battery bootup. Plug in any USB-C PD adapter between 15W to 100W. The default highest PD power profile is 45W (15V/3A). Follow the steps to read the USB-C and charger statuses after the dead-battery bootup:

• Dead-battery setup – Supply the BATT+ and BATT- pins with 5.5V (the battery is fully depleted when the battery drops below 5.6V). Plug in a USB-C PD power adapter (preferably USB-compliant). Connect the GUI to the reference design (Figure 46).
• VBUS during dead-battery bootup (Figure 47).
• Read the USBC Status and observe the V_BUS ADC (Figure 48).
• Go to the Command tab → Select Current SrcCap (0x30) and click Write to read the selected PDO and current source capabilities of the far-end device (Figure 49).
• Read the charger status and configurations (Figure 50 and Figure 51).