Datasheet

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Table Of Contents

This is information on a product in full production.

June 2012 Doc ID 13844 Rev 5 1/29

ST1S10

3 A, 900 kHz, monolithic synchronous step-down regulator IC

Datasheet − production data

Features

■ Step-down current mode PWM regulator

■ Output voltage adjustable from 0.8 V

■ Input voltage from 2.5 V up to 18 V

■ 2% DC output voltage tolerance

■ Synchronous rectification

■ Inhibit function

■ Synchronizable switching frequency from 400

kHz up to 1.2 MHz

■ Internal soft start

■ Dynamic short circuit protection

■ Typical efficiency: 90%

■ 3 A output current capability

■ Stand-by supply current: max 6 µA over

temperature range

■ Operative junction temp: from - 40 °C to 125 °C

Applications

■ Consumer

– STB, DVD, DVD recorders, TV, VCR, car

audio, LCD monitors

■ Networking

– XDSL, modems, DC-DC modules

■ Computer

– Optical storage, HD drivers, printers,

audio/graphic cards

■ Industrial and security

– Battery chargers, DC-DC converters, PLD,

PLA, FPGA, LED drivers

Description

The ST1S10 is a high efficiency step-down PWM

current mode switching regulator capable of

providing up to 3 A of output current. The device

operates with an input supply range from 2.5 V to

18 V and provides an adjustable output voltage

from 0.8 V (V

) to 0.85*V

IN_SW

OUT

*(1+R1/R2)]. It operates either at a 900 kHz

fixed frequency or can be synchronized to an

external clock (from 400 kHz to 1.2 MHz). The

high switching frequency allows the use of tiny

SMD external components, while the integrated

synchronous rectifier eliminates the need for a

Schottky diode. The ST1S10 provides excellent

transient response, and is fully protected against

thermal overheating, switching over-current and

output short circuit.

The ST1S10 is the ideal choice for point-of-load

regulators or LDO pre-regulation.

PowerSO-8

DFN8 (4 x 4 mm)

Table 1. Device summary

Part number

Order codes

DFN8 (4 x 4 mm) PowerSO-8

ST1S10 ST1S10PUR ST1S10PHR

www.st.com

Summary of content (29 pages)

PAGE 1
ST1S10 3 A, 900 kHz, monolithic synchronous step-down regulator IC Datasheet − production data Features ■ Step-down current mode PWM regulator ■ Output voltage adjustable from 0.8 V ■ Input voltage from 2.5 V up to 18 V ■ 2% DC output voltage tolerance ■ Synchronous rectification ■ Inhibit function ■ Synchronizable switching frequency from 400 kHz up to 1.
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Contents ST1S10 Contents 1 Application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2 Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 4 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 5 Application information . . . . . . . . . .
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ST1S10 List of tables List of tables Table 1. Table 2. Table 3. Table 4. Table 5. Table 6. Table 7. Table 8. Table 9. Table 10. Device summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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List of figures ST1S10 List of figures Figure 1. Figure 2. Figure 3. Figure 4. Figure 5. Figure 6. Figure 7. Figure 8. Figure 9. Figure 10. Figure 11. Figure 12. Figure 13. Figure 14. Figure 15. Figure 16. Figure 17. Figure 18. Figure 19. Figure 20. Figure 21. Figure 22. Figure 23. Figure 24. Figure 25. Figure 26. Figure 27. 4/29 Typical application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PAGE 5
ST1S10 Application circuit 1 Application circuit Figure 1. Typical application circuit L1 3.3µH 12V 5V – 3A VIN_SW SW C1 4.7µF EN ST1S10 R1 VIN_A C2 22µF FB C3 R2 0.
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Pin configuration ST1S10 2 Pin configuration Figure 2. Pin connections (top view for PowerSO-8, bottom view for DFN8) DFN8 (4x4) Table 2. PowerSO-8 Pin description Pin n° Symbol 1 VIN_A 2 INH (EN) 3 VFB 4 AGND Analog ground 5 SYNC Synchronization and frequency select. Connect SYNC to GND for 900 kHz operation, or to an external clock from 400 kHz to 1.2 MHz. (see Sync operation paragraph 5.8.
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ST1S10 Maximum ratings 3 Maximum ratings Table 3. Absolute maximum ratings Symbol Value Unit Positive power supply voltage -0.3 to 20 V VIN_A Positive supply voltage -0.3 to 20 V VINH Inhibit voltage -0.3 to VIN_A V VSW Output switch voltage -0.3 to 20 V VFB Feedback voltage -0.3 to 2.5 V IFB FB current -1 to +1 mA Sync Synchronization -0.
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Electrical characteristics 4 ST1S10 Electrical characteristics VIN = VIN_SW = VIN_A = VINH = 12 V, VSYNC = GND, VOUT = 5 V, IOUT = 10 mA, CIN = 4.7 µF +0.1 µF, COUT = 22 µF, L1 = 3.3 µH, TJ = -40 to 125°C (Unless otherwise specified, refer to the typical application circuit. Typical values assume TJ = 25°C). Table 5.
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ST1S10 Table 5. Symbol Electrical characteristics Electrical characteristics (continued) Parameter Test conditions Min. SYNC input threshold high VIN = 2.5 V to 18 V 1.6 IIL, IIH SYNC input current VIN = 2.5 V to 18 V, VSYNC = 0 or 5 V -10 UVLO Under voltage lock-out threshold VIH_SYNC Typ. Max. Unit V +10 µA VIN rising 2.3 V Hysteresis 200 mV 1. Guaranteed by design, but not tested in production. 2. See output voltage selection paragraph 5.5 for maximum duty cycle conditions.
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Application information ST1S10 5 Application information 5.1 Description The ST1S10 is a high efficiency synchronous step-down DC-DC converter with inhibit function. It provides up to 3 A over an input voltage range of 2.5 V to 18 V, and the output voltage can be adjusted from 0.8 V up to 85% of the input voltage level. The synchronous rectification removes the need for an external Schottky diode and allows higher efficiency even at very low output voltages. A high internal switching frequency (0.
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ST1S10 Application information Equation 2 D = (VOUT + VF) / (VIN-VSW) where VF is the voltage drop across the internal NMOS, and VSW represents the voltage drop across the internal PDMOS. The minimum duty cycle (at VIN_max) and the maximum duty cycle (at VIN_min) should be considered in order to determine the max IRMS flowing through the input capacitor. A minimum value of 4.7 µF for the VIN_SW and a 0.1 µF ceramic capacitor for the VIN_A are suitable in most application conditions.
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Application information ST1S10 Also, the capacitor ESL value impacts the output ripple voltage, but ceramic capacitors usually have very low ESL, making ripple voltages due to the ESL negligible. In order to reduce ripple voltages due to the parasitic inductive effect, the output capacitor connection paths should be kept as short as possible. The ST1S10 has been designed to perform best with ceramic capacitors.
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ST1S10 Application information recommended to select a VOUT level which maintains the junction temperature below the thermal shut-down protection threshold (150°C typ.) at the rated output current. The following equation can be used to calculate the junction temperature (TJ): Equation 8 TJ = {[VOUT x IOUT x RthJA x (1-η)] / η} +TAMB where RthJA is the junction-to-ambient thermal resistance, ηis the efficiency at the rated IOUT current and TAMB is the ambient temperature.
PAGE 14
Application information ST1S10 MHz from an external clock applied to the SYNC pin. When the SYNC feature is not used, this pin must be connected to ground with a path as short as possible to avoid any possible noise injected in the SYNC internal circuitry. 5.8.2 Inhibit function The inhibit pin can be used to turn OFF the regulator when pulled down, thus drastically reducing the current consumption down to less than 6 µA.
PAGE 15
ST1S10 Application information Figure 3. Application schematic for heavy capacitive load L1 3.3µH 12V C4 (*) 4.7nF VIN_SW 5V – 3A SW C1 EN 10µF ST1S10 R1 LOAD VIN_A C2(*) 22µF FB C3 CLOAD R2 4.7µF SYNC AGND Output Load PGND (*) see OCP and SCP descriptions for C2 and C4 selection. Figure 4. Application schematic for low output voltage (VOUT < 2.5 V) and 2.5 V < VIN < 8 V L1 2.2µH VIN<8V 0.8V
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Layout considerations 6 ST1S10 Layout considerations Layout is an important step in design for all switching power supplies. High-speed operation (900 kHz) of the ST1S10 device demands careful attention to PCB layout. Care must be taken in board layout to get device performance, otherwise the regulator could show poor line and load regulation, stability issues as well as EMI problems. It is critical to provide a low inductance, impedance ground path.
PAGE 17
ST1S10 Figure 7. Layout considerations PCB layout suggestion IOUT Common ground node for power ground Power Ground IIN 6.1 Thermal considerations The lead frame die pad, of ST1S10, is exposed at the bottom of the package and must be soldered directly to a properly designed thermal pad on the PCB, the addition of thermal vias from the thermal pad to an internal ground plane will help increase power dissipation.
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Diagram ST1S10 7 Diagram Figure 8.
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ST1S10 8 Typical performance characteristics Typical performance characteristics Unless otherwise specified, refer to the typical application circuit under the following conditions: TJ = 25°C, VIN = VIN-SW = VIN-A = VINH = 12 V, VSYNC = GND, VOUT = 5 V, IOUT = 10 mA, CIN = 4.7 µF + 0.1 µF, COUT = 22 µF, L1 = 3.3 µH Figure 9. Voltage feedback vs. temperature 1.2 820 1.1 Frequency [MHz] 830 810 VFB [mV] Figure 10. Oscillator frequency vs. temperature 800 790 780 VIN=VINH=12V, VOUT=0.
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Typical performance characteristics ST1S10 Figure 13. Reference line regulation vs. temperature Figure 14. Reference load regulation vs. temperature 1.3 Load [%VOUT /I OUT ] Line [%(V OUT /VIN)] 0.2 0.1 0 -0.1 VIN-A=VIN-SW=VINH from 2.5 to 20V, VOUT=0.8V, IOUT=10mA -0.2 -50 -25 0 25 50 75 100 VIN-A=VIN-SW=VINH=12V, IOUT from 10mA to 3A 1 0.7 0.4 0.1 -0.2 -0.5 -25 125 0 25 TEMPERATURE [°C] VIN-A=VIN-SW=12V, VINH=GND, VOUT=0.8V 5 4 3 2 VIN-A=VIN-SW=12V, VINH=1.2V, VOUT=0.
PAGE 21
ST1S10 Typical performance characteristics Figure 20. Efficiency vs. output current@Vout = 5 V 100 100 90 90 EFFICIENCY [%] EFFICIENCY [%] Figure 19. Efficiency vs. temperature 80 70 60 VIN-A=VIN-SW=VINH=12V, VOUT=5V, IOUT=3A 50 -50 -25 0 25 50 75 80 70 60 VIN-A=VIN-SW=VINH=12V, VOUT=5V, TJ=25°C 100 50 125 0 0.5 TEMPERATURE [°C] Figure 21. Efficiency vs. output current@Vout = 3.3 V 1.5 2 2.5 3 2.5 3 Figure 22. Efficiency vs.
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Package mechanical data 9 ST1S10 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: www.st.com. ECOPACK® is an ST trademark. Table 6. Power SO-8 (exposed pad) mechanical data mm Dim. Min. Typ. A 1.70 A1 0.00 A2 1.25 b 0.31 0.51 c 0.17 0.25 D 4.80 D1 0.15 4.90 5.
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ST1S10 Package mechanical data Figure 23.
PAGE 24
Package mechanical data ST1S10 Figure 24.
PAGE 25
ST1S10 Package mechanical data Table 7. Power SO-8 (exposed pad) tape and reel mechanical data mm Dim. Min. Typ. A Max. 330 C 12.8 D 20.2 N 60 13.2 T 22.4 Ao 8.1 8.5 Bo 5.5 5.9 Ko 2.1 2.3 Po 3.9 4.1 P 7.9 8.1 Figure 25.
PAGE 26
Package mechanical data Table 8. ST1S10 DFN8 (4X4) mechanical data mm. Dim. Min. Typ. Max. A 0.80 0.90 1.00 A1 0 0.02 0.05 A3 0.20 b 0.23 0.30 0.38 D 3.90 4.00 4.10 D2 2.82 3.00 3.23 E 3.90 4.00 4.10 E2 2.05 2.20 2.30 e L 0.80 0.40 0.50 0.60 Figure 26.
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ST1S10 Package mechanical data Table 9. DFN8 (4x4)tape and reel mechanical data mm Dim. Min. Typ. A Max. 330 C 12.8 D 20.2 N 99 13.2 101 T 14.4 Ao 4.35 Bo 4.35 Ko 1.1 Po 4 P 8 Figure 27.
PAGE 28
Revision history 10 ST1S10 Revision history Table 10. Document revision history Date Revision Changes 28-Aug-2007 1 Initial release. 24-Sep-2007 2 Add RthJC on Table 4. 25-Oct-2007 3 Added new paragraph 6: Layout considerations. 16-Mar-2010 4 Updated PowerSO-8 package mechanical data. 31-May-2012 5 Updated SO-8 (epad)and DFN8 (4x4) mechanical data. Changed temperature min from 25 °C to 40 °C in Table 4, and in Section 4.
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ST1S10 Please Read Carefully: 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.