ST EVAL5981 User Manual
EVAL5981
1 A step-down switching regulator demonstration board based on the L5981
Features
■1 A DC output current
■2.9 V to 18 V input voltage
■Output voltage adjustable from 0.6 V to 16 V
■250 kHz switching frequency, programmable up to 1 MHz
■Internal soft-start and inhibit
■Low dropout operation: 100 % duty cycle
■Zero-load current operation
■Over-current and thermal protection
■VFQFPN8 3 mm x 3 mm package
Data Brief
EVAL5981
Description
The EVAL5981 demonstration board provides the design engineer with a fully functional step-down switching regulator with an output current of up to 1 A. The L5981 integrates STMicroelectronics step-down switching regulator, together with all the external components required for a typical application.
The rated voltage of the input capacitor and the Schottky diode rectifier repetitive peak reverse voltage are both 25 V, making the board capable of covering the entire 2.9 V - 18 V input voltage range of the L5981 device.
The board features an external resistor divider (R1 and R2) designed for an output voltage of 3.3 V.
The output voltage can be set to a level from 0.6 V up to the rated voltage of the output capacitor (16 V).
The compensation network on the demonstration board allows the use of MLCC as output filter to keep the loop stable. The inductor saturation current and forward current of the Schottky diode are within the current limit values.
The switching frequency on the demonstration board is set to 500 kHz by means of the R5 resistor connected to pin Fsw.
March 2009 |
Rev 1 |
1/6 |
For further information contact your local STMicroelectronics sales office. |
www.st.com |
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EVAL5981 |
EVAL5981 application circuit and component list |
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1 EVAL5981 application circuit and component list
Figure 1. Application circuit
VIN=3.3V to 18V |
VCC |
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OUT |
L1 |
15uH |
Vout=3.3V |
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8 |
1 |
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D1 |
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INH |
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SYNCH |
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3 |
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2 |
STPS2L25U |
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L5981 |
C2 |
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GND |
7 |
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FB |
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R1 4.99K |
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C1 |
C6 |
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22uF |
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5 |
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6 |
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10uF |
68nF |
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4 |
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C4 10nF |
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FSW |
COMP |
R3 180 |
C3 3.3nF |
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R4 3.9K |
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R5 100K |
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R2 1.1K |
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C5 150pF |
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Table 1. |
Component list |
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Reference |
Part number |
Description |
Manufacturer |
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C1 |
GRM31CR61E106KA12 |
10 μF, 25 V |
MURATA |
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C2 |
GRM32ER61E226KE15 |
22 μF, 25 V |
MURATA |
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C3 |
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3.3 nF, 50 V |
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C4 |
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10 nF, 50 V |
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C5 |
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150 pF, 50 V |
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C6 |
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68 nF, 25 V |
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R1 |
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4.99 kΩ, 1 %, 0.1 W 0603 |
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R2 |
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1.1 kΩ, 1 %, 0.1 W 0603 |
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R3 |
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180 Ω, 1 %, 0.1 W 0603 |
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R4 |
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3.9 kΩ, 1 %, 0.1 W 0603 |
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R5 |
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100 kΩ, 1 %, 0.1 W 0603 |
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D1 |
STPS2L25V |
2 A, 25 V |
STMicroelectronics |
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L1 |
7447779115 |
15 μH, 20 %, 2.2 A |
Wurth elektronik |
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2/6
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