应用笔记 6064

MAX32550 Current Measurement Breakdown of Peripherals

By: Reza Ahmadi

摘要 : This application note provides the information on a typical power consumption use case of the MAX32550 evaluation kit (EV kit) under certain conditions. Moreover, a table summarizing the breakdown of current consumption per interface is provided.


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Introduction

Usually the power consumption numbers in the datasheet of a chip are not a good representation of real-life application. This application note tries to explain the setup and typical conditions under which the measurements are taken for the MAX32550 EV kit. At the end, the results are presented in graphical form.

Setting Up

To measure the current on the single power supply of the board, jumper JP17 of the MAX32550 EV kit is removed and based on the test of a digital ammeter inserted between the jumper heads or a current probe clamped to a small jumper wire connected across JP17.

Testing

Let the MAX32550 power up normally. As it goes through different sequences such as secure boot, loading code, and running freeRTOS, the current is measured during each operation. This data is presented in Figure 1. The different operations are clearly marked on this figure.

Current profile during power-up and running freeRTOS. Figure 1. Current profile during power-up and running freeRTOS.

The breakdown of average power consumption for each operation per supply rail is presented in Table 1.

Table 1. Breakdown of Average Power and Current Consumption Per Operations

Current Consumption on 3.3V (mA) Total Power for Each Operation (mW)
Operation Power up 60 200
Code Authentication 80 265
Running code (freeRTOS) 64 212
Smartcard Transaction 1 3.3
Magnetic Card Transaction 1 3.3
STOP Mode 0.560 1.8

Table 2. Breakdown of Average Power Consumption Per Peripherals

VDD = 3.3V (µA) (typ) Total Power for Each Block (mW)
Interface GPIO (each) 416 1.4
USB 480 1.6
Color TFT 2,970 9.8
DMA Controller 2,870 9.4
SPI (each) 320 1.0
UART (each) 280 0.9
Magnetic Stripe 4,280 1.0
Smart Card Controller 390 1.3
I2C 280 0.9
Crypto Block 1,950 6.4
Timers (each) 130 0.4
Mono LCD 110 0.4
Keyboard Controller 100 0.3
ADC 50 0.15
DAC 510 1.68

The breakdown of the current per peripheral is shown graphically in Figure 2.

Breakdown of average current consumption per peripherals. Figure 2. Breakdown of average current consumption per peripherals.

Conclusion and Observations

  • Turning off the PLL reduces the current from 64mA to 13mA
  • The highest contributions to total current are the MSR, color TFT, DMA controller, and the cryptography engine.
  • Smart card operation and magnetic card reading have very little effect on the power rails.
  • The 3.3V rail is mainly plateaued at 64mA.
  • STOP mode power consumption is around 230mW

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