LMZ3170x Power Module Evaluation Module User's Guide

Trademarks

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1 Description

This EVM features the LMZ31710 (10-A), LMZ31707 (7-A), or LMZ31704 (4-A) synchronous buck power module configured for operation with typical 5-V and 12-V input bus applications. The output voltage can be set to one of seven popular values by using a configuration jumper. In similar fashion, the switching frequency can be set to one of seven values with a jumper. The full output current rating of the device can be supplied by the EVM. Input and output capacitors are included on the board to accommodate the entire range of input and output voltages. Monitoring test points are provided to allow measurement of the following:

Efficiency
Power dissipation
Input ripple
Output ripple
Line and load regulation
Transient response

Control test points are provided for use of the PWRGD, inhibit/UVLO, synchronization, and slow-start/tracking features of the LMZ317xx device. The EVM uses a recommended PCB layout that maximizes thermal performance and minimizes output ripple and noise.

2 Getting Started

Figure 2-1 highlights the user interface items associated with the EVM. The polarized PVin Power terminal block (TB1) is used for connection to the host input supply and the polarized Vout Power terminal block (TB2) is used for connection to the load. These terminal blocks can accept up to 16-AWG wire. The polarized Vbias terminal block (TB3) is used along with the VIN select jumper (P1) when optional split power supply operation is desired. Refer to the LMZ317xx data sheets (LMZ31710 10-A Module, 2.95-V to 17-V Input and Current Sharing in QFN Package Data Sheet, LMZ31707 7-A Power Module with 2.95-V to 17-V Input Current Sharing in QFN Data Sheet, and LMZ31704 4-A Power Module with 2.95-V to 17-V Input and Current Sharing Data Sheet) for further information on split power supply operation.

Figure 2-1 LMZ317xxEVM User Interface

The PVin Monitor and Vout Monitor test points located near the power terminal blocks are intended to be used as voltage monitoring points where voltmeters can be connected to measure PVin and Vout. The voltmeter references should be connected to any of the four PVin/Vout Monitor Grounds test points located between the power terminal blocks. Do not use these PVin and Vout monitoring test points as the input supply or output load connection points. The PCB traces connecting to these test points are not designed to support high currents.

The PVin Scope and Vout Scope test points can be used to monitor PVin and Vout waveforms with an oscilloscope. These test points are intended for use with un-hooded scope probes outfitted with a low-inductance ground lead (ground spring) mounted to the scope barrel. The two sockets of each test point are on 0.1 in centers. The scope probe tip should be connected to the socket labeled PVin or Vout, and the scope ground lead should be connected to the socket labeled PGND.

The Controls test points located directly below the device are made available to test the features of the device. Any external connections made to these test points should be referenced to the Control Ground test point located along the bottom of the EVM. Refer to Section 3 for more information on the individual control test points.

The Vout Select jumper (P3) and Fsw Select jumper (P2) are provided for selecting the desired output voltage and appropriate switching frequency. Before applying power to the EVM, ensure that the jumpers are present and properly positioned for the intended output voltage. Refer to Table 2-1 for the recommended jumper settings. Always remove input power before changing the jumper settings.

Once the jumper settings have been confirmed, configure the host input supply to apply the appropriate bus voltage listed in Table 2-1 and confirm that the selected output voltage is obtained.

Table 2-1 Output Voltage and Switching Frequency Jumper Settings

VOUT Select	F_SW Select	PVin Bus Voltage
5.0 V	1 MHz	12 V
3.3 V	750 kHz	5 V or 12 V
2.5 V	750 kHz	5 V or 12 V
1.8 V	500 kHz	5 V or 12 V
1.2 V	300 kHz	5 V or 12 V
0.9 V	250 kHz	5 V or 12 V
0.6 V	200 kHz	5 V or 12 V

3 Test Point Descriptions

Twelve wire-loop test points and two scope probe test points have been provided as convenient connection points for digital voltmeters (DVM) or oscilloscope probes to aid in the evaluation of the device. A description of each test point follows:

Table 3-1 Test Point Descriptions⁽¹⁾

Test Point	Description
PVIN	Input voltage monitor. Connect DVM to this point to measure efficiency.
VOUT	Output voltage monitor. Connect DVM to this point to measure efficiency, line regulation, and load regulation.
AGND	Input and output voltage monitor grounds (located between terminal blocks). Reference the above DVMs to any of these four analog ground points.
PVIN Scope (J1)	Input voltage scope monitor. Connect an oscilloscope to this set of points to measure input ripple voltage.
VOUT Scope (J2)	Output voltage scope monitor. Connect an oscilloscope to this set of points to measure output ripple voltage and transient response.
PWRGD	Monitors the power-good signal of the device. This is an open-drain signal that requires an external pullup resistor if monitoring is desired. A 10-kΩ to 100-kΩ pullup resistor is recommended. PWRGD is high if the output voltage is within 92% to 107% of its nominal value.
INH/UVLO	Connect this point to control ground to inhibit the device. Allow this point to float to enable the device. An external resistor divider can be connected between this point, control ground, and VIN to adjust the UVLO of the device.
RT/CLK	Connects to the RT/CLK pin of the device. An external clock signal can be applied to this point to synchronize the device to an appropriate frequency.
SS/TR	Connects to the internal slow-start capacitor of the device. An external capacitor can be connected from this point to control ground to increase the slow-start time of the device. This point can also be used to track applications.
SYNC_OUT	This output provides a clock signal that is 180° out of phase with the PH node of the device and can be used to synchronize other devices.
AGND	Control ground (located along bottom of EVM). Reference any signals associated with the control test points to this analog ground point.

(1) Refer to the LMZ317xx data sheets for absolute maximum ratings associated with these features.