Texas instruments TPS8804EVM User Manual

1 Introduction

The TPS8804EVM is used to evaluate the TPS8804 smoke and CO detector analog front end (AFE) and power management IC. The EVM allows for easy connection from the TPS8804 to a user-supplied photoelectric chamber and carbon monoxide sensor. The TPS8804 GUI interfaces with the EVM to quickly evaluate the photo amplifier, LED driver, and CO amplifier performance, and other blocks with the register map. For a more thorough evaluation, an external microcontroller can be connected to the TPS8804EVM to create a smoke detection system.

1.1 Applications

• Smoke and CO detectors

1.2 Features

• Dual LED drivers for blue and IR LEDs

• Wide bandwidth, low offset photodiode amplifier

• Ultra-low power CO transimpedance amplifier

• LDOs for internal analog blocks and external microcontroller

• Single buffered analog output AMUX for CO and photo signals

• Serial interface for configuring amplifiers, drivers, regulators

• SLC interface for power line communication

• Under-voltage, over-temperature fault monitors

• Wide input voltage range for flexible power supply configuration

User's Guide

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Using the TPS8804EVM

1.3 Recommended Equipment

• 4.5-V to 15.5-V power supply capable of 100mA

• USB2ANY™ interface adaptor

• TPS880x GUI software – Installation files are available in the TPS8804EVM product folder

• Multimeter for measuring regulator voltages and CO amplifier output

• Oscilloscope for measuring photodiode signal pulse shape

2 Setup

Specific connections on the TPS8804EVM board require configuration before starting the evaluation.

2.1 Sensor Connections

TI recommends connecting a photoelectric smoke chamber and CO sensor to the TPS8804EVM for the evaluation. The TPS8804EVM has a built-in photodiode (D7), blue LED (D8), and IR LED (D6) for functional testing. These components can be de-soldered in order to connect a photoelectric chamber photodiode, IR LED, and/or blue LED its place. Ensure the photodiode wires are kept short to preserve signal integrity.

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Setup

The CO sensor is connected to J17 screw terminals with the sensor counter terminal tied to AGND.

2.2 Jumper and Switch Configurations

The S1 switch position determines the VMCU voltage at power-up. Ensure that only one S1 sub-switch is in the ON position. Table 1 displays the VMCU voltage corresponding with each S1 switch position. For proper operation with the USB2ANY adapter, set VMCU to 3.3 V with sub-switch 4.

Table 1. VMCU Power-up Voltage

S1 Switch Position VMCU

1 1.5V 2 1.8V 3 2.5V 4 3.3V

The J2 jumper connects VSLC to VCC. A single supply connected to VCC powers the entire EVM with the jumper connected.

The J6 jumper selects the I2C device address. Connect J6 to the AGND position to set the address to 0x3F. Connect J6 to the VMCU position to set the address to 0x2A. The GUI is compatible with both options and defaults to 0x2A.

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Setup

2.3 Power Connection

Connect the power supply to VCC and PGND. Set the power supply to 5 V, 100 mA. Enable the power supply and measure the voltage on VMCU (TP27) to ensure it is operating at the voltage option selected by S1:

• 1.5 V

• 1.8 V

• 2.5 V

• 3.3 V

See Table 1 for more information on the initial VMCU voltage.

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Figure 1. Switch, Jumper, and Power Connections

Using the TPS8804EVM

Setup

2.4 USB2ANY Connection

Use a USB cable to connect the USB2ANY adapter to a computer with the TPS880x GUI installed. Open the TPS880x GUI and verify the USB2ANY adapter is recognized (see Figure 2). With the EVM powered, connect the USB2ANY adapter to the EVM using the USB2ANY adapter 10-pin ribbon cable. Click EXPLORE TPS8804EVM then QUICK START and select the device address corresponding to the J6 jumper (see Section 2.2). Send the test command to verify the EVM, USB2ANY adapter, and GUI software are all connected.

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Figure 2. TPS880x GUI Connected to USB2ANY Adapter

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Analog Evaluation

3 Analog Evaluation

Click START EVALUATION and select the feature to evaluate. The Analog Front End section guides the CO AFE and photo AFE evaluation. Enter the register map to evaluate the other blocks in the TPS8804 device.

Figure 3. Test Command Successful

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Analog Evaluation

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3.1 CO AFE Evaluation

If a CO sensor is available, connect it to the J17 terminal block. Select the feedback resistance and reference voltage in the GUI software. The TPS8804EVM default configuration uses the internal resistors and references. To use an external feedback resistor, solder a resistor to R5. To use an external input resistor, replace the R1 0-Ω resistor with the required input resistance. The output resistor filters the CO amplifier output when a capacitor is installed on C3.

Set the AMUX SELECTION to CO AMPLIFIER. Enable the CO amplifier and measure the voltage on AMUX_BUF.

Figure 4. Evaluation Selection Menu

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Analog Evaluation

Figure 5. CO Amplifier Settings

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Figure 6. Clean Air CO Amplifier Output

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Analog Evaluation

3.1.1 CO Connectivity Test

A simple test confirms that the CO sensor is connected to the EVM. Remove the shunt connected to J7 and connect a shunt to J15 and J16. Write COTEST_EN = 1 and measure the pulse shape on AMUX_BUF using an oscilloscope. When COTEST_EN = 1, the PREF pin is pulled low and injects charge into the CO sensor and amplifier. The AMUX pulse shape is different if the CO sensor is disconnected. Write COTEST_EN = 0, remove the J15 and J16 shunts, and connect the J7 shunt when finished.

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Figure 7. COTEST_EN Register Bit

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