4 Power Stage

The Multi-Phase Power Board power stage features four identical output channels. These are known as the board's “Phases” and are labeled A through D.

Each phase can be independently controlled through the adapter connector, and provides options for voltage and current feedback.


Power Stage Performance
Voltage Range	6V to 50V
Power⁽¹⁾	10A at 24V
Note: 1: Typical performance in base configuration.

4.1 Phase Output


Each output phase consists of two N-channel power MOSFETs (SIR120DP by Vishay) arranged in a half-bridge configuration. The gates are controlled by a Microchip MIC4605-1 half-bridge MOSFET driver, allowing individual control of the high and low side MOSFETs while providing shoot-through protection. The control signals are available through the adapter connector. Pull-down resistors are mounted close to the MIC4605, so neither MOSFET is active by default, causing the phase output to float. Each phase has a ten mΩ low-side current sense resistor routed into the on-board current sense system.

Figure 4-1. Half Bridge Functional Diagram

Table 4-1. Key MOSFET Parameters
SIR120DP Summary
V_DS	80V
R_{DS_(ON)} max. at V_GS= 10V	0.00355Ω
Q_g typ.	48.5 nC
I_D	106A

Table 4-2. Half Bridge Drive Connections
Phase	Signal	Position on Adapter Connector
A	Drive A High	26
A	Drive A Low	25
B	Drive B High	24
B	Drive B Low	23
C	Drive C High	22
C	Drive C Low	21
D	Drive D High	20
D	Drive D Low	19

4.2 Voltage Feedback

The MPPB’s power stage provides voltage feedback options for each phase and includes a configurable virtual neutral point for back EMF measurements.

4.2.1 Phase Voltage Sense


The instantaneous output voltage of each phase is routed through a resistor divider before being exposed on the adapter connector.

Info: The phase output voltages are divided by 16 to bring them within 0-3.3V for the full V_Supply range.

Table 4-3. Phase Voltage Connections
Phase	Signal Name	Position on Adapter Connector
A	Feedback A	12
B	Feedback B	10
C	Feedback C	8
D	Feedback D	6

4.2.2 Virtual Neutral Point


The 3-phase virtual neutral point is implemented using resistors and provides an instantaneous average voltage of the three phases connected to it. In the out-of-box configuration, phases A, B and C are connected to the virtual neutral. Other configurations are possible by modifying the board and moving the 0805-size 0-Ohm resistors.

Info: The virtual neutral point output voltage is divided by 16 to bring it within 0-3.3V for the full V_Supply range.

Table 4-4. Virtual Point Connection
Phase	Signal Name	Position on Adapter Connector
Virtual Neutral Point	Feedback N	4

4.3 Phase Current Sense

The Multi-Phase Power Board features two independent current sense amplifiers, implemented using MCP6021op-amps in a differential summing configuration around a reference voltage.

The number of phases connected to each amplifier is configurable and will influence the transfer function as per Table 4-5.

Table 4-5. Amplifier Transfer Functions
# Phases Connected	Amplifier Gain	Transfer Function
1Ph	15	$V_{CS} = V_{REF} - \frac{3}{20} I_{PH1}$
2Ph	10	$V_{CS} = V_{REF} - \frac{1}{10} (I_{PH1} + I_{PH2})$
3Ph	7.5	$V_{CS} = V_{REF} - \frac{3}{40} (I_{PH1} + I_{PH2} + I_{PH3})$

4.3.1 Current Sense Amplifier 1


Current Sense Amplifier 1 can connect to phases A, B and C. In the out-of-box configuration, it is connected to all three. Other configurations are possible by modifying the board and moving the 0805-size 0-Ohm resistors.

Figure 4-3. Current Sense 1 Block Diagram

Table 4-6. Current Sense 1 Connection
Position on Adapter Connector	Silk Screen Marking
7	CS1

4.3.2 Current Sense Amplifier 2


Current Sense Amplifier 2 can connect to phases B, C and D. In the out-of-box configuration it is connected only to phase D. Other configurations are possible by modifying the board and moving the 0805-size 0-Ohm resistors.

Figure 4-4. Current Sense 2 Block Diagram

Table 4-7. Current Sense 2 Connection
Position on Adapter Connector	Silk Screen Marking
5	CS2

4.3.3 Voltage Reference


The voltage reference generates the midpoint voltage for the current sense amplifiers. It is implemented as a voltage divider feeding into an MCP6021 op-amp configured as a unity gain amplifier. The Vref circuit output is also available on the adapter connector as an ADC reference.

Info: The voltage reference output voltage is 1.65V.

Table 4-8. Vref Connection
Position on Adapter Connector	Silk Screen Marking
3	VREF