AS1331-BTDT-25 AMSCO [austriamicrosystems AG], AS1331-BTDT-25 Datasheet - Page 10

• Manufacturer Part Number: AS1331-BTDT-25
• Description: 300mA Buck-Boost Synchronous DC/DC Converters
• Manufacturer: AMSCO [austriamicrosystems AG]

AS1331
Datasheet - D e t a i l e d D e s c r i p t i o n
8 Detailed Description
The synchronous buck-boost converter AS1331 uses a Power Save Mode control technique to reach a high efficiency
over a wide dynamic range of load currents. The output voltage is monitored by a comparator with 3% accuracy. The
Power Save Mode puts the device into “sleep mode” when V
Meaning, the switching is stopped and only quiescent current is drawn from the power source. The switching is started
again when V
The numbers of current pulses which are necessary to load the output capacitor are set by the value of the output
capacitor, the load current, and the comparator hysteresis (~1%).
Figure 23. AS1331 - Block Diagram - Fixed Output Voltage
Modes of Operation
When V
inductor current reaches approximately 400mA. In the next step SW A and SW D are closed and depending on the
difference between V
V
V
V
If the inductor current is not 0mA, the transistors SW B and SW D are closed to ramp down the current to zero. If V
is still below the threshold voltage the next cycle is started. If I
and SW D are closed until the inductor current is 600mA.
Note: The 4-switch-mode (SW A+SW C => SW B+SW D => SW A + SW C...) and also the buck-mode (SW A+SW D
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IN
IN
IN
> V
~ V
< V
OUT
OUT
OUT
=> SW B+SW D => SW A+SW D...) are never used.
OUT
: The inductor current is going up to 600mA.
: The device stops after 2µs.
: The inductor current falls down to 0mA.
drops below the reference threshold, the AS1331 switches on the transistors SW A and SW C until the
OUT
VIN
EN
drops below the reference threshold and the output capacitor is charged again.
IN
1.6V
V
600mA
and V
IN
Peak
Current
Limit
OUT
UVLO
AS1331
the inductor current raises, falls or stays constant.
Shutdown
SW A
SW1
SW B
Thermal Shutdown
Machine
State
Logic
Revision 1.03
and
Gate Drivers
Conduction
Anticross
OUT
MAX
and
PGND
is above its programmed reference threshold.
(600mA) wasn’t reached in the previous cycle, SW A
V
BEST
VOUT
Comp
SW C
V
BEST
SW2
GND
SW D
IZERO
Detect
1.25V
V
V
R1
OUT
IN
R2
FB
VOUT
10 - 16
OUT