L5983 STMicroelectronics, L5983 Datasheet
L5983
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L5983 Summary of contents
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... Application circuit November 2010 1.5 A step-down switching regulator VFQFPN8 Description The L5983 is a step-down switching regulator with a 2.0 A (min.) current limited embedded power MOSFET able to deliver an output current in excess of 1 the load. The input voltage can range from 2 while the output voltage can be set starting from ...
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... Inductor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 5.3 Output capacitor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 5.4 Compensation network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 5.4.1 5.4.2 5.5 Thermal considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 5.6 Layout considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 5.7 Application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 6 Application ideas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 6.1 Positive buck-boost . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 6.2 Inverting buck-boost . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 2/43 Type III compensation network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Type II compensation network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Doc ID 13005 Rev 7 L5983 ...
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... L5983 7 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 8 Order codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 9 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 Doc ID 13005 Rev 7 Contents 3/43 ...
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... Vout to the FB pin. The switching frequency can be increased connecting an external resistor from the FSW pin and ground. If this pin is left floating the deice works at its free-running frequency of 250 kHz. Ground Unregulated DC input voltage CC Doc ID 13005 Rev GND GND FSW FSW FB FB Description L5983 ...
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... L5983 2 Maximum ratings 2.1 Absolute maximum ratings Table 2. Absolute maximum ratings Symbol V CC OUT F , COMP, SYNCH SW INH FB P TOT stg 2.2 Thermal data Table 3. Thermal data Symbol R thJA 1. Package mounted on demonstration board. Parameter Input voltage Output DC voltage Analog pin Inhibit pin ...
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... Values Min Typ Max 2.9 18 2.9 0.175 0.3 140 170 140 220 2.0 2.3 2.6 225 250 275 220 275 1.254 0 100 1000 (1) 0.593 0.6 0.607 2 0.6 1.9 7.5 10 7.4 8.2 9.1 2 L5983 Unit V mΩ A kHz V % kHz V mA μA V μA ms ...
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... L5983 Table 4. Electrical characteristics Symbol V High level output voltage CH V Low level output voltage CL I Bias source current FB I Source COMP pin O SOURCE I Sink COMP pin O SINK G Open loop voltage gain V Synchronization function High input voltage Low input voltage Slave sink current ...
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... Functional description 4 Functional description The L5983 is based on a “voltage mode”, constant frequency control. The output voltage V is sensed by the feedback pin (FB) compared to an internal reference (0.6 V) providing OUT an error signal that, compared to a fixed frequency sawtooth, controls the ON and OFF time of the power switch ...
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... L5983 4.1 Oscillator and synchronization Figure 4 shows the block diagram of the oscillator circuit. The internal oscillator provides a constant frequency clock. Its frequency depends on the resistor externally connected to the FSW pin. In case the FSW pin is left floating the frequency is 250 kHz; it can be increased ...
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... Functional description Figure 5. Sawtooth: voltage and frequency feed forward; external synchronization Figure 6. Oscillator frequency vs. FSW pin resistor 10/43 Doc ID 13005 Rev 7 L5983 ...
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... L5983 4.2 Soft-start The soft-start is essential to assure correct and safe startup of the step-down converter. It avoids inrush current surge and makes the output voltage increase monothonically. The soft-start is performed by a staircase ramp on the non-inverting input (V amplifier. So the output voltage slew rate is: ...
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... III compensation network has to be used (see network selection). However, the methodology to compensate the loop is to introduce zeros to obtain a safe phase margin. 12/43 GBWP Slew rate Section 5.4 Doc ID 13005 Rev 7 L5983 Value 100 dB 4.5 MHz 7 V/μ 3 mA/40 mA for details of the compensation ...
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... L5983 4.4 Overcurrent protection The L5983 implements the overcurrent protection sensing current flowing through the power MOSFET. Due to the noise created by the switching activity of the power MOSFET, the current sensing is disabled during the initial phase of the conduction time. This avoids an erroneous detection of a fault condition. This interval is generally known as “masking time” ...
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... The thermal shutdown block generates a signal that turns off the power stage if the junction temperature goes above 150 °C. Once the junction temperature goes back to about 130 °C, the device restarts in normal operation. The sensing element is very close to the PDMOS area, therefore ensuring an accurate and fast temperature detection. 14/43 compatible. CC Doc ID 13005 Rev 7 L5983 ...
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... L5983 5 Application information 5.1 Input capacitor selection The capacitor connected to the input must be able to support the maximum input operating voltage and the maximum RMS input current required by the device. The input capacitor is subject to a pulsed current, the RMS value of which is dissipated over its ESR, affecting the overall system efficiency ...
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... The maximum current ripple, at OFF = the maximum output 1 D – F MIN ⋅ ---------------------- - OFF = 250 kHz, the minimum SW Δ ------- - 2 Saturation current (A) 3.3 to 6.8 2. 3.2 to 3.6 3.3 to 6.2 2 2.9 to 3.6 4 2 2.5 to 3.7 4 2 2.5 to 2.8 L5983 ...
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... L5983 5.3 Output capacitor selection The current in the capacitor has a triangular waveform which generates a voltage ripple across it. This ripple is due to the capacitive component (charge and discharge of the output capacitor) and the resistive component (due to the voltage drop across its ESR). So the output capacitor must be selected in order to have a voltage ripple compliant with the application requirements ...
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... Compensation network The compensation network has to assure stability and good dynamic performance. The loop of the L5983 is based on the voltage mode control. The error amplifier is a voltage operational amplifier with high bandwidth. So, by selecting the compensation network the E/A is considered as ideal, that is, its bandwidth is much larger than that of the system. ...
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... L5983 Equation 15 As seen in Section following paragraphs the guidelines to select the type II and type III compensation network are illustrated. Figure 9. Error amplifier, PWM modulator and LC output filter V V REF REF FB FB 5.4.1 Type III compensation network The methodology to stabilize the loop consists of placing two zeros to compensate the effect of the LC double pole, therefore increasing phase margin ...
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... Calculate C 4 20/43 ( · G (f) · G LOOP PW0 LC , usually between 1 kΩ and 5 kΩ order to have the required bandwidth (BW), that means ⋅ ----------------- - placing the zero the output filter double pole frequency (f Doc ID 13005 Rev 7 PW0 (f)) is given. TYPEIII ⋅ 1 L5983 · ...
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... L5983 Equation 19 4. Calculate C 5 Equation 20 5. Set the first pole also at four times the system bandwidth and also the second zero at the output filter double pole: Equation 21 The suggested maximum system bandwidth is equal to the switching frequency divided by 3.5 (F /3.5), but lower than 100 kHz if the F ...
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... Application information Figure 12. Open loop gain Bode diagram with ceramic output capacitor 22/43 Doc ID 13005 Rev 7 L5983 ...
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... L5983 5.4.2 Type II compensation network If the equivalent series resistance (ESR) of the output capacitor introduces a zero with a frequency lower than the desired bandwidth (that is: 2π * ESR * C helps stabilize the loop. Electrolytic capacitors show not negligible ESR (>30 mΩ), so with this kind of output capacitor the type II network combined with the zero of the ESR allows the loop to be stabilized ...
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... R = ⎝ ⎠ ESR f = ------------------------------------------- - ⋅ ESR 2π ESR C by placing the zero one decade below the output filter double pole ------------------------------ - 4 ⋅ 2π order to place the second pole at four times the system bandwidth 3 Doc ID 13005 Rev ⋅ ⋅ -------- - ⋅ OUT ⋅ L5983 ...
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... L5983 Equation 25 For example, with V mΩ, the type II compensation network is: In Figure 15 the module and phase of the open loop gain is shown. The bandwidth is about 30 kHz and the phase margin is 45° ------------------------------------------------------------- - ⋅ ⋅ 5 2π 1 μ 3 OUT 1.1kΩ 249Ω ...
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... Application information Figure 15. Open loop gain Bode diagram with electrolytic/tantalum output capacitor 26/43 Doc ID 13005 Rev 7 L5983 ...
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... L5983 5.5 Thermal considerations The thermal design is important to prevent the thermal shutdown of the device if junction temperature goes above 150 °C. The three different sources of losses within the device are: a) conduction losses due to the not negligible R equal to: Equation 26 where D is the duty cycle of the application and the maximum R Note that the duty cycle is theoretically given by the ratio between quite higher to compensate the losses of the regulator ...
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... Thanks to the exposed pad of the device, the ground plane helps to reduce the thermal resistance junction to ambient large ground plane enhances the thermal performance of the converter allowing high power conversion. In Figure 17 a layout example is shown. 28/43 , measured on the demonstration board described in the following Doc ID 13005 Rev 7 L5983 ...
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... L5983 Figure 17. Layout example Doc ID 13005 Rev 7 Application information 29/43 ...
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... Vout=3.3V Vout=3.3V Vout=3.3V Vout=3. STPS2L25U STPS2L25U STPS2L25U STPS2L25U R1 4.99K R1 4.99K R1 4.99K R1 4.99K R3 330 R3 330 R3 330 R3 330 C3 2.2nF C3 2.2nF C3 2.2nF C3 2.2nF R2 1.1K R2 1.1K R2 1.1K R2 1.1K Description Manufacturer 10 μ MURATA 22 μ MURATA 2 220 pF nF Coilcraft STMicroelectronics L5983 22uF 22uF 22uF 22uF ...
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... L5983 Figure 19. PCB layout (component side) Figure 20. PCB layout (bottom side) Figure 21. PCB layout (front side) Doc ID 13005 Rev 7 Application information 31/43 ...
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... Figure 27. Efficiency vs. output current 95 Vo=3.3V 90 Vo=2.5V 85 Vo=1. 1.2 1.4 1.6 1 Doc ID 13005 Rev 7 current Vo=5V Vo=3.3V Vo=2.5V VCC=12V, F =250kHz SW 0.2 0.4 0.6 0.8 1.0 1.2 1.4 Io [A] Vo=2.5V Vo=1.8V Vo=1.2V VCC=3.3V, F =250kHz SW 0.2 0.4 0.6 0.8 1 1.2 1.4 Io [A] L5983 1.6 1.8 1.6 1.8 ...
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... L5983 Figure 28. Load regulation 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 0.2 0.4 0.6 0.8 I [A] O Figure 30. Load transient: from 300 OUT OUT OUT OUT AC coupled AC coupled AC coupled AC coupled 100mV/div 100mV/div 100mV/div 100mV/div 0.5A/div 0.5A/div 0.5A/div 0.5A/div Load slew rate = 2.5A/us Load slew rate = 2 ...
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... Application ideas 6.1 Positive buck-boost The L5983 can implement the step-up/down converter with a positive output voltage. Figure 33 shows the schematic: one power MOSFET and one Schottky diode are added to the standard buck topology to provide 12 V output voltage with input voltage from 2 ...
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... L5983 Equation 32 where I is the average current in the embedded power MOSFET in the ON time chose the right value of the inductor and to manage transient output current, which for a short time can exceed the maximum output current calculated by current in the power MOSFET must also be calculated. The peak current, shown in 33, must be lower than the minimum current limit (2 ...
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... V D external power MOSFET. 6.2 Inverting buck-boost The L5983 can implement the step-up/down converter with a negative output voltage. Figure 33 shows the schematic to regulate - further external components are added to the standard buck topology. The relationship between input and output voltage is: ...
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... L5983 As in the positive one, in the inverting buck-boost the current flowing through the power MOSFET is transferred to the load only during the OFF time. So according to the maximum DC switch current (1.5 A), the maximum output current can be calculated from where the duty cycle is given by Figure 35 ...
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... Application ideas Figure 36. Maximum output current according to max DC switch current (1.5 A 38/43 Doc ID 13005 Rev 7 L5983 ...
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... L5983 7 Package mechanical data In order to meet environmental requirements, ST offers these devices in different grades of ® ECOPACK packages, depending on their level of environmental compliance. ECOPACK specifications, grade definitions and product status are available at registered trademark. Doc ID 13005 Rev 7 Package mechanical data www.st.com. ECOPACK 39/43 ...
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... Doc ID 13005 Rev 7 L5983 inch Min Typ Max 0.0315 0.0354 0.0394 0.0008 0.0020 0.0276 0.0079 0.0071 0.0091 0.0118 0.1161 0.1181 0.1200 0.0878 0.0937 ...
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... L5983 8 Order codes Table 11. Order codes Order codes L5983 L5983TR Package VFQFPN8 ( 1.08 mm) Doc ID 13005 Rev 7 Order codes Packaging Tube Tube and reel 41/43 ...
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... Table 4 on page 5 Added: Section 6 on page 34 7 Updated: Figure 19, Doc ID 13005 Rev 7 Changes Figure 2 on page 4, Figure 8 on page Figure 17 on page 29, Figure 18 on page and Figure 18 on page 30 and Figure 6 on page 10 Figure 20 and Figure 21 on page 31 L5983 14, 30, ...
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... L5983 Information in this document is provided solely in connection with ST products. STMicroelectronics NV and its subsidiaries (“ST”) reserve the right to make changes, corrections, modifications or improvements, to this document, and the products and services described herein at any time, without notice. All ST products are sold pursuant to ST’s terms and conditions of sale. ...