LP3907SQ-JXQXEV National Semiconductor, LP3907SQ-JXQXEV Datasheet - Page 6

• Manufacturer Part Number: LP3907SQ-JXQXEV
• Description: LP3907 EVALUATION BOARD
• Manufacturer: National Semiconductor
• Series: PowerWise®r

Specifications of LP3907SQ-JXQXEV

• Main Purpose: DC/DC, Step Down with LDO
• Outputs And Type: 4, Non-Isolated
• Current - Output: 1A, 600mA, 300mA, 300mA
• Regulator Topology: Buck
• Frequency - Switching: 2.1MHz
• Board Type: Fully Populated
• Utilized Ic / Part: LP3907
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Voltage - Output: -
• Voltage - Input: -
• Power - Output: -

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REGULATOR OUTPUT VOLTAGE SELECTION
The output voltages of all the LDO and buck converters can
be programmed through I
ing the slider. The buck regulators have 2 sliders and a Hold/
Ramp button to control its output voltage. This prevents the
user from scaling the bucks to the second voltage if the Hold/
Ramp button is not depressed. The output of the buck regu-
lator will reflect the setting of the slider that has its radio button
clicked (V1 or V2).
The buck regulators also have a Hold/Ramp slider that de-
termines how fast the regulators scale to the 2nd programmed
voltage. The ramp time is measured from the time the chip
receives the I
ton.
All of the regulators can also be hardware enabled or disabled
via different configuration settings on the 20 pin header (de-
scribed in the Hardware section of this report). The buck
regulators also have additional enable test points on the
board.
2
C signals from clicking the opposing radio but-
2
C control registers by simply mov-
FIGURE 7. Regulator Output Voltage Selection Interface
6
The user can also force the bucks into PWM mode. Clicking
the Force PWM check box on the GUI forces the respective
regulator to stay in PWM mode even in the case of a light load
(PFM mode). Forced PWM will be disabled by clicking the
“Force PWM” check-box again.
The buck converters have a slider interface to provide an ad-
justable output voltage. By sliding the bar to the bottom of the
slider, the user can use an external resistor divider network
for setting the Bucks output voltage.
Force PWM mode is not recommended when a battery is
powering the system.
The USB interface also contains ADCs to measure the output
voltage of the regulators. To do so, simply connect the USB
interface ADC jumpers shown in Figure 8. To measure the
external voltages again, simply click the “Measure” button on
the GUI.
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