Datasheet

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October 2011 Doc ID 022197 Rev 2 1/22

STBB1-AXX

1 A, high efficiency single inductor

dual mode buck-boost DC-DC converter

Features

■ Buck-boost DC-DC converter

■ Operating input voltage range from 2.0 V to

5.5 V

■ 2% DC feedback voltage tolerance

■ Synchronous rectification

■ Shutdown function

■ 1.5 MHz switching frequency

■ Power save mode at light load

■ Typical efficiency: > 94%

■ 1 A output current capability

■ Shutdown current < 1 µA

■ Available in DFN10 (3 x 3 mm)

Applications

■ Single cell Li-Ion and 3 cells alkaline, Ni-MH

powered devices

■ SD/MMC memory card supply

■ Palmtop computers

■ Cell phones

■ Digital cameras

Description

The STBB1-A is a fixed frequency, high efficiency,

buck-boost DC-DC converter able to provide

output voltages ranging from 1.2 V to 5.5 V and

input voltages from 2.0 V to 5.5 V. The device can

operate with input voltages higher than, equal to,

or lower than the output voltage making the

product suitable for single lithium-Ion, multicell

alkaline or NiMH applications where the output

voltage is within the battery voltage range. The

integrated low-R

DSon

N-channel and P-channel

MOSFET switches contribute to its high efficiency.

The MODE pin allows selecting between auto

mode and forced PWM mode thus taking benefit

either of lower power consumption or best

dynamic performance. The device includes also

soft-start control, thermal shutdown and current

limit. The STBB1-A is packaged in DFN10 (3 x 3

mm).

DFN10 (3 x 3 mm)

Table 1. Device summary

Order code Marking Output voltage

STBB1-APUR BB1-A ADJ

www.st.com

Summary of content (22 pages)

PAGE 1
STBB1-AXX 1 A, high efficiency single inductor dual mode buck-boost DC-DC converter Features ■ Buck-boost DC-DC converter ■ Operating input voltage range from 2.0 V to 5.5 V ■ 2% DC feedback voltage tolerance ■ Synchronous rectification ■ Shutdown function ■ 1.
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Contents STBB1-AXX Contents 1 Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3 Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4 Typical application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5 Electrical characteristics . . . . . . . . . .
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STBB1-AXX Block diagram 1 Block diagram Figure 1. STBB1-A block diagram VIN SW1 VOUT SW2 Gate Control Current sensor Oscillator FB Modulator VREF VINA MODE/SYNC DEVICE CONTROL Temp.
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Absolute maximum ratings STBB1-AXX 2 Absolute maximum ratings Table 2. Absolute maximum ratings Symbol Parameter Value Unit Input voltage - 0.3 to 7 V Output voltage - 0.3 to 7 V SW1, SW2 DC voltage - 0.3 to 7 V FB DC voltage - 0.3 to 1.5 V MOD/SYNC, EN DC voltage - 0.
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STBB1-AXX Pin configuration 3 Pin configuration Figure 2. Pin connections (top through view) Table 4. Pin description Pin n° Symbol Name and function 1 VOUT Output voltage 2 SW2 Switch pin - Internal switches are connected to this pin. Connect inductor between SW1 to SW2 3 PGND 4 SW1 Switch pin - Internal switches are connected to this pin. Connect inductor between SW1 and SW2 5 VIN Power input voltage.
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Typical application STBB1-AXX 4 Typical application Figure 3. Application circuit - adjustable output version L SW2 SW1 VIN OUT Vin CIN VOUT COUT R1 VinA STBB1-APUR EN FB MODE/SYN R2 GND PGND AM07860v1 Figure 4.
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STBB1-AXX Typical application List of external components (1) Table 5. Component Manufacturer Part number Value Size CIN Murata GRM21BR71A106KE51L 10 µF 0805 COUT Murata GRM21BR60J226ME39L 22 µF 0805 TDK VLCF4020T-2R2N1R7 L 4 x 4 x 2 mm 2.2 µH Coilcraft XFL4020-222ME R1 560 kΩ (VO = 3.3 V) R2 100 kΩ 4 x 4 x 2 mm (2) 0402 0402 1. Above listed components refer to typical application. Operation of the STBB1-A is not limited to the choice of these external components. 2.
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Electrical characteristics 5 STBB1-AXX Electrical characteristics VIN = VINA = VEN = 3.6 V, CIN = 10 µF, COUT = 10 µF, L = 2.2 µH, TJ = - 40 to 85°C (unless otherwise specified; typical values are referred to TA = 25 °C). Table 6. Symbol VIN Electrical characteristics Parameter Test conditions Input voltage range Min. 2.0 VINA rising VUVLO VOUT Output voltage range ZFB FB input impedance TJ = 25°C 1.80 1.50 1.60 485 500 515 mV 490 500 510 mV 5.5 V 1.2 10 MΩ 250 FB = 0.
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STBB1-AXX Table 6. Symbol ν TSHDN THYS Electrical characteristics Electrical characteristics (continued) Parameter Efficiency, VIN = 3.6 V, VOUT = 3.3 V Test conditions Min. Typ. IOUT = 10 mA; VMODE = 0 89 IOUT = 10 mA; VMODE = VIN 67 IOUT = 100 mA; VMODE = VIN 94 Max.
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Detailed description STBB1-AXX 6 Detailed description 6.1 General description The STBB1-A is a high efficiency dual mode buck-boost switch mode converter. Thanks to the 4 internal switches, 2 P-channel and 2 N-channel, and its unique control mechanisms it is able to deliver e well-regulated output voltage using a variable input voltage which can be higher than, equal to or lower than the desired output voltage.
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STBB1-AXX 6.3 Detailed description External synchronization The STBB1-A implements external synchronization pin. If and external clock signal is applied to the MODE (SYN) pin with a frequency between 1.35 MHz and 2.0 MHz and with proper low/high levels, the device automatically goes in PWM mode and the external clock is used as switching oscillator. 6.4 Enable pin The device operates when EN pin is set high. If EN pin is set low the device stops switching, all the internal blocks are turned off.
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Typical performance characteristics STBB1-AXX 7 Typical performance characteristics Figure 5. L = 2.2 µH, VO = 3.3 V, all measurements done with circuit shown in Figure 3 and external components listed in Table 5. Efficiency vs. IOUT in auto mode Figure 6. Efficiency vs. IOUT in PWM mode 100 100 90 80 90 Efficiency [%] Efficiency [%] 70 80 70 60 50 40 30 VIN = 3.6 V VIN = 2.2 V 60 VIN = 3.6 V VIN = 5.0 V VIN = 2.2 V 20 VIN = 5.
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STBB1-AXX Typical performance characteristics Figure 11. Boost region operation Figure 12. Buck-boost region operation SW1 3 V/div SW1 3 V/div SW2 3 V/div SW2 3 V/div IL 0.2 A/div IL 0.2 A/div VO 20 mV/div AC Coupled VO 100 mV/div AC Coupled TIMEBASE: 1µs/div TIMEBASE: 0.5µs/div VIN = 2.5 V VO = 3.3 V IO = 200 mA, PWM mode VIN = 3.6 V VO = 3.3 V IO = 100 mA, pulse skipping mode Figure 13. Buck-boost region operation Figure 14.
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Application information STBB1-AXX 8 Application information 8.1 Programming the output voltage The STBB1-A is available in two versions: fixed output voltage (STBB1-APURXX) and adjustable output voltage (STBB1-APUR). In the first case the device integrates the resistor divider needed to set the correct output voltage. This allows the saving of 2 external components. The FB pin must be connected directly to VOUT.
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STBB1-AXX Application information The minimum inductor value for the application is the higher between Equation 2 and Equation 3. In addition to the inductance value the maximum current the inductor can handle must be calculated in order to avoid saturation. Equation 4 IPEAK −BUCK = (IOUT / η) + VOUT × ( VIN MAX − VOUT ) 2 × VIN MAX × fs × L Equation 5 IPEAK −BOOST = VOUT × IOUT VINMIN × (VOUT − VINMIN ) + η × VINMIN 2 × VOUT × fs × L Where η is the estimated efficiency of STBB1-A.
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Recommended PCB layout 9 STBB1-AXX Recommended PCB layout Figure 17. Component placement Figure 18. Top layer routing Figure 19.
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STBB1-AXX 10 Package mechanical data 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.
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Package mechanical data STBB1-AXX DFN10 (3x3 mm) mechanical data mm. mils. Dim. A Min. Typ. Max. Min. Typ. Max. 0.80 0.90 1.00 31.5 35.4 39.4 0.02 0.05 0.8 2.0 0.65 0.80 25.6 31.5 A1 A2 0.55 A3 21.7 0.20 7.9 b 0.18 0.25 0.30 7.1 9.8 11.8 D 2.85 3.00 3.15 112.2 118.1 124.0 D2 2.20 E 2.85 118.1 124.0 E2 1.40 e L ddd 86.6 3.00 3.15 112.2 1.75 55.1 0.50 0.30 0.40 68.9 19.7 0.50 0.08 11.8 15.7 19.7 3.
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STBB1-AXX Package mechanical data Tape & reel QFNxx/DFNxx (3x3) mechanical data mm. inch. Dim. Min. Typ. A Max. Min. Typ. 180 13.2 7.087 C 12.8 D 20.2 0.795 N 60 2.362 T 0.504 0.519 14.4 0.567 Ao 3.3 0.130 Bo 3.3 0.130 Ko 1.1 0.043 Po 4 0.157 P 8 0.315 Doc ID 022197 Rev 2 Max.
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Different output voltage versions of the STBB1-A available on request STBB1-AXX 11 Different output voltage versions of the STBB1-A available on request Table 7. Options available on request 20/22 Order codes Marking Output voltages STBB1-APUR18 BB1 18 1.8 V STBB1-APUR25 BB1 25 2.5 V STBB1-APUR28 BB1 28 2.8 V STBB1-APUR33 BB1 33 3.
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STBB1-AXX Revision history 12 Revision history Table 8. Document revision history Date Revision Changes 07-Sep-2011 1 First release. 04-Oct-2011 2 Added condition TA= 25 °C for the oscillator frequency parameter in Table 6 on page 8.
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STBB1-AXX 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.