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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
DFN10 (3 x 3 mm)
integrated low-RDSon 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).
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
Table 1. Device summary
Order code
Marking
STBB1-APUR
BB1-A
Output voltage
ADJ
October 2011
Doc ID 022197 Rev 2
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Contents
Contents
STBB1-AXX
1 Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2 Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3 Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4 Typical application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
6 Detailed description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
6.1 General description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
6.2 Dual mode operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
6.3 External synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6.4 Enable pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6.5 Protection features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6.5.1 Soft-start and short-circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6.5.2 Undervoltage lockout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6.5.3 Over-temperature protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
7 Typical performance characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
8 Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
8.1 Programming the output voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
8.2 Inductor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
8.3 Input and output capacitor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
9 Recommended PCB layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
10 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
11 Different output voltage versions of the STBB1-A
available on request . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
12 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2/22 Doc ID 022197 Rev 2

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STBB1-AXX
1 Bloc
k diagram
Figure 1. STBB1-A block diagram
VIN
Block diagram
SW1
SW2
VOUT
VINA
MODE/SYNC
EN
Oscillator
Current
sensor
Modulator
DEVICE
CONTROL
Temp.
Control
GND
Gate
Control
VREF
FB
PGND
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Absolute maximum ratings
2 Absolute maximum ratings
STBB1-AXX
Table 2. Absolute maximum ratings
Symbol
Parameter
VINA, VIN
VOUT
SW1, SW2
Input voltage
Output voltage
DC voltage
FB
MOD/SYNC, EN
TJ
TSTG
TJOP
ESD
DC voltage
DC voltage
Maximum junction temperature
Storage temperature range
Operating junction temperature range
Human body model
Value
- 0.3 to 7
- 0.3 to 7
- 0.3 to 7
- 0.3 to 1.5
- 0.3 to 7
150
- 65 to + 150
- 40 to + 85
2
Unit
V
V
V
V
V
°C
°C
°C
kV
Note:
Absolute maximum ratings are those values beyond which damage to the device may occur.
Functional operation under these conditions is not implied.
Table 3. Thermal data
Symbol
Parameter
RthJC
RthJA
Thermal resistance junction-case
Thermal resistance junction-ambient
Value
2.96
30.9
Unit
°C/W
°C/W
4/22 Doc ID 022197 Rev 2

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STBB1-AXX
3 Pin configuration
Figure 2. Pin connections (top through view)
Pin configuration
Table 4.
Pin n°
1
2
3
4S
5V
6E
7
8
9
10
Pin description
Symbol
VOUT
SW2
PGND
W1
IN
N
MODE
(SYNC)
VINA
GND
FB
Exposed pad
Name and function
Output voltage
Switch pin - Internal switches are connected to this pin. Connect inductor
between SW1 to SW2
Power ground
Switch pin - Internal switches are connected to this pin. Connect inductor
between SW1 and SW2
Power input voltage. Connect a ceramic bypass capacitor (10 µF minimum)
between this pin and PGND
Enable pin. Connect this pin to GND or a voltage lower than 0.4 V to shut down
the IC. A voltage higher than 1.2 V is required to enable the IC.
Operation mode selection.
If MODE pin is low, the STBB1-A automatically switches between pulse
skipping and fixed frequency PWM according to the load level.
If MODE pin is pulled high, the STBB1-A works always in PWM mode.
When a square waveform is applied, this pin provides the clock signal for
oscillator synchronization
Supply voltage for control stage
Signal ground
Feedback voltage
Power ground
Doc ID 022197 Rev 2
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