Datasheet

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This is information on a product in full production.

August 2013 DocID023280 Rev 3 1/28

ST1S15

500 mA, 6 MHz synchronous step-down converter

Datasheet

production data

Features

• 85% typical efficiency

• 500 mA output current capability

• 45 µA typical quiescent current

• PFM or PWM operation for best efficiency over

whole load range

• Ultra-fast load and line transient

• Short-circuit and thermal protection

• Tiny external components

• Auto or forced PWM selection with dedicated

• Available in Flip Chip 6 and DFN6 (2 x 2 mm)

packages

Applications

• DSP and multimedia processors core supply

• Cell phones

• PDAs

Description

The ST1S15 is a high efficiency miniaturized

step-down converter able to provide 500 mA

output current from an input voltage from 2.3 V to

5.5 V. This converter is specifically designed for

applications where high efficiency and small a

application area are the key factors. With an

output voltage as low as 0.6 V the device

supports low voltage DSPs and processors core

supply. Due to the 6 MHz switching frequency the

ST1S15 can use nominal values of 470 nH for the

inductor and 4.7 µF for the output capacitor,

providing, at the same time, very good

performance in terms of load and line transients.

It is possible to select a PFM mode for high

efficiency under light load conditions or PWM

mode for tight regulation and best dynamic

performance. Short-circuit and thermal protection

are also included.

DFN6 (2 x 2 mm)

Flip Chip 6

Table 1. Device summary

Order codes

Output

voltages (V)

Packages

ST1S15J18R 1.82

Flip Chip 6

ST1S15J28R 2.8

ST1S15TPUR 1.82

DFN6 (2 x 2 mm)

ST1S15-28TPUR 2.8

www.st.com

Summary of content (28 pages)

PAGE 1
ST1S15 500 mA, 6 MHz synchronous step-down converter Datasheet - production data Flip Chip 6 DFN6 (2 x 2 mm) Features applications where high efficiency and small a application area are the key factors. With an output voltage as low as 0.6 V the device supports low voltage DSPs and processors core supply. Due to the 6 MHz switching frequency the ST1S15 can use nominal values of 470 nH for the inductor and 4.
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Contents ST1S15 Contents 1 Application schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5 Typical performance characteristics . . . . . .
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ST1S15 1 Application schematic Application schematic Figure 1. ST1S15 application schematic VIN VOUT L SW VIN CIN ST1S15 COUT FB EN GND MODE AM11904v1 Table 2. Typical external components Component Manufacturer Part number Value Size CIN Murata GRM155R60J475ME87 4.7 µF 0402 COUT Murata 4.7 µF 0402 L Murata 470 nH 2.0 x 1.25 x 0.5 mm GRM155R60G475ME87 (1) GRM155R60J475ME87 LQM21PNR47MC0D 1. For VOUT ≤ 1.82 V. Note: All the above components refer to a typical application.
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Pin configuration 2 ST1S15 Pin configuration Figure 2. Pin connections (top view) MARKING VIEW BUMPS VIEW A1 A2 A2 A1 B1 B2 B2 B1 C1 C2 C2 C1 AM11909v1 AM11911v1 Table 3. Pin description Pin name Flip Chip DFN6 4/28 Description VIN A2 1 High-side switch connection and IC supply. EN B2 2 ENABLE pin with positive logic. The IC goes into shutdown if pulled low. Do not leave this pin floating. GND C2 3 Power and IC supply ground. FB C1 4 Feedback input.
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ST1S15 3 Maximum ratings Maximum ratings Table 4. Absolute maximum ratings Symbol Parameter Value Unit Power and signal supply voltage - 0.3 to + 6.0 V Logic input pins - 0.3 to + 6.0 V -0.3 to VIN + 0.3 V Operating ambient temperature - 40 to 85 °C TJ Junction temperature - 40 to 150 °C TSTG Storage temperature - 65 to 150 °C VIN EN, MODE FB, SW TAMB Note: Feedback and switching pins Absolute maximum ratings are those values beyond which damage to the device may occur.
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Electrical characteristics 4 ST1S15 Electrical characteristics - 40 °C < TA < 85 °C, CIN = 4.7 µF nominal, COUT = 4.7 µF nominal, L = 470 nH, typical values are at TA = 25 °C, VEN = VIN unless otherwise specified. Table 7. Electrical characteristics Symbol Parameter Test conditions Min. Typ. Max. Unit 5.5 V 2.2 V 60 µA General section VIN VUVLO IQ fSW Operating input voltage range Undervoltage lockout threshold 1.8 1.
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ST1S15 Electrical characteristics Table 7. Electrical characteristics (continued) Symbol Parameter VOUT_Ri Peak-to-Peak output voltage ripple pple ILKFB VIN_TR Test conditions Typ. Max. Unit PWM mode, IOUT = 150 mA, VIN = 3.6 V, VOUT = 1.82 V 10 mV PFM mode, IOUT = 150 mA, VIN = 3.6 V, VOUT = 1.82 V 30 mV FB pin leakage current VFB = 5.5 V Line transient response. Output voltage variation over nominal DC level. tR = tF = 10 µs Case 1: VIN = 2.5 to 3.1 V Case 2: VIN = 3.9 to 4.
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Typical performance characteristics 5 ST1S15 Typical performance characteristics Figure 4. Efficiency vs. output current (VOUT = 2.8 V) 100 100 90 80 70 60 50 40 30 20 10 0 90 80 Vin= 2.5V PWM Mode Vin= 2.5V PFM Mode Vin= 3.6V PWM Mode Vin= 3.6V PFM Mode Vin= 4.5V PWM Mode 10 50 40 30 20 Vin= 5.5V PWM Mode 10 I OUT [mA] 100 Vin= 3.2V PWM Mode Vin= 3.2V PFM Mode Vin= 3.6V PWM Mode Vin= 3.6V PFM Mode Vin= 4.2V PWM Mode Vin= 4.2V PFM Mode Vin= 5.0V PWM Mode Vin= 5.0V PFM Mode 60 Vin= 4.
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ST1S15 Typical performance characteristics Figure 7. Supply current vs. input voltage in PWM mode Figure 8. Output voltage vs. output current 100 1.85 Vin = 2.5 V Output Voltage [V] ISupply [mA] 1.84 10 T= 85 °C T= 25 °C Vin = 3.6 V Vin = 4.5 V 1.83 1.82 1.81 T= 0°C 1.8 T= -40 °C 1.79 0 1 2 2.5 3 3.5 4 4.5 5 5.5 50 100 150 6 200 250 300 350 400 450 500 550 Output Current [mA ] Input Voltage [V] VEN = VIN, Mode = VIN, VOUT = 1.82 V VIN = 2.3 V to 5.
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Typical performance characteristics ST1S15 Figure 13. Mode transition PWM to PFM Figure 14. Output voltage ripple Mode VIN V OUT IL VIN = 3.6 V, VOUT = 1.82 V, Mode = 3.6 to 0 V, Load = 180 Ω VIN = 3.6 V, VOUT = 1.82 V, Mode = GND, VEN = VIN, No load Figure 15. Output voltage ripple Figure 16. Line transient VOUT IOUT VIN = 3.6 V, VOUT = 1.82 V, IOUT = 500 mA, VEN = VIN 10/28 VIN = 3.9 to 4.
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ST1S15 Typical performance characteristics Figure 17. Load transient IOUT = 50 to 250 mA Figure 18. Load transient IOUT = 250 to 50 mA , V OUT VOUT IOUT IOUT VIN = 3.6 V, tr = 100 ns, IOUT = 50 mA to 250 mA, VEN = VIN, Mode = GND VIN = 3.6 V, tf = 100 ns, IOUT = 250 mA to 50 mA, VEN = VIN, Mode = GND Figure 19. Enable startup Figure 20. VIN startup EN IOUT VIN VOUT VIN IL VOUT VIN = 3.6 V, Enable = 0 to 3.6 V, Mode = VIN, VOUT = 1.82 V, Load = 3.6 Ω VIN = 0 to 2.
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Block schematic 6 ST1S15 Block schematic Figure 21. Block schematic EN Enable & Soft Start V-I Reference & Prereg + UVLO VIN Current Limit & Short Protect. MODE PFM - Analog timing PFM - PWM Switch Control Logic Driver & Anti X-Cond SW Thermal Protect. Oscill. & Sawtooth Vref_PFM FB PWM Comparator R1 GND Error Amp & Comp.
PAGE 13
ST1S15 Detailed description 7 Detailed description 7.1 General description The ST1S15 is a fixed voltage mode PWM step-down DC-DC converter which operates with typically 6 MHz fixed frequency pulse width modulation (PWM) at moderate to heavy load currents. At light load currents the converter can automatically enter PFM (pulse frequency mode) mode. To make the device work, few components are required: an inductor and two capacitors.
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Detailed description ST1S15 The transition from PWM to PFM mode occurs when the load current decreases and the coil current becomes negative. After the zero-crossing output goes up for 127 consecutive times the device switches to PFM mode. Figure 23. PWM to PFM transition IL 127 Zero-Crossing output pulses MODE t PWM PFM I LOAD t 500 mA High Load Light Load t AM11907v1 7.
PAGE 15
ST1S15 7.6 Detailed description Thermal protection The device also has thermal shutdown protection, which is active when the junction temperature reaches 125 °C. In this case both the high and low-side MOSFETs are turned off. Once the junction temperature goes back below 95 °C, the device resumes normal operation. 7.7 Overcurrent protection The overcurrent protection is used to limit the maximum inductor current.
PAGE 16
Application Information ST1S15 8 Application Information 8.1 Input and output capacitor It is recommended to use ceramic capacitors with X5R or X7R dielectric and low ESR. The input capacitor is used to filter any disturbance present in the input line and to obtain stable operation. The output capacitor is very important to satisfy the output voltage ripple requirement.
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ST1S15 Layout guidelines Due to the high switching frequency and peak current, the layout is an important design step for all switching power supplies. If the layout is not done carefully, important parameters such as stability, efficiency, line and load regulation and output voltage ripple may be compromised. Short, wide traces must be implemented for main current and for power ground paths.
PAGE 18
Package mechanical data 9 ST1S15 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 9. DFN6 (2 x 2 mm) mechanical data (mm) Dim. Min. Typ. Max. A 0.51 0.55 0.60 A1 0 0.02 0.05 b 0.18 0.25 0.30 D D2 2.00 1.30 E E2 18/28 1.55 2.
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ST1S15 Package mechanical data Figure 26.
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Package mechanical data ST1S15 Figure 27.
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ST1S15 Package mechanical data Table 10. Flip Chip 6 mechanical data (mm) Dim. Min. Typ. Max. A 0.52 0.56 0.6 A1 0.17 0.20 0.23 A2 0.35 0.36 0.37 b 0.23 0.25 0.29 D 1.16 1.19 1.22 D1 0.8 e 0.4 E 0.905 0.935 E1 0.4 fD 0.272 fE 0.200 ccc 0.075 DocID023280 Rev 3 0.
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Package mechanical data ST1S15 Figure 28.
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ST1S15 Package mechanical data Figure 29.
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Package mechanical data ST1S15 Tape & reel QFNxx/DFNxx (2x2 mm) mechanical data mm. inch. Dim. Min. Typ. A Min. Typ. 180 13.2 Max. 7.087 C 12.8 D 20.2 0.795 N 60 2.362 T 24/28 Max. 0.504 0.519 14.4 0.567 Ao 2.1 2.2 2.3 0.083 0.087 0.091 Bo 2.1 2.2 2.3 0.083 0.087 0.091 Ko 0.65 0.75 0.85 0.026 0.030 0.033 Po 4 0.157 P 4 0.
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ST1S15 Package mechanical data Tape & reel Flip-Chip 6 mechanical data mm. Dim. Min. Typ. A Max. 180 C 12.8 D 20.2 N 60 13.2 T 14.4 Ao 1.01 1.06 1.11 Bo 1.26 1.31 1.36 Ko 0.61 0.66 0.71 Po 3.9 4.1 P 3.9 4.
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Different output voltage versions of the ST1S15 available on request 10 Different output voltage versions of the ST1S15 available on request Options available on request: 26/28 – 0.8 V – 1V – 1.05 V – 1.2 V – 1.25 V – 1.5 V – 1.8 V – 1.85 V – 1.875 V – 2.5 V – 3V – 3.
PAGE 27
ST1S15 11 Revision history Revision history Table 11. Document revision history Date Revision 07-Jun-2012 1 First release. 04-Mar-2013 2 Modified: D1 and E1 values Table 10 on page 21. 3 Updated Table 1: Device summary on page 1, Table 7: Electrical characteristics on page 6, Section 9: Package mechanical data and Section 10: Different output voltage versions of the ST1S15 available on request. Minor text changes.
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ST1S15 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.