AS1302
Datasheet - Detailed Description
8 Detailed Description
Functional Description
The AS1302 is a high efficiency and low noise switched capacitor DC-DC converter that is capable of boost operation.
It is equipped with two built-in coupled H-bridge type switch configurations. Based on the value of the output voltage
the system automatically initiates mode-switching to achieve the highest possible efficiency. The regulation of the
output voltage is achieved by a regulation loop, which modulates the current drive capability of the power transistors so
that the amount of charge transferred from the input to the output at each clock cycle is controlled and is equal to the
charge needed by the load.
Regulation Loop
The AS1302 operates at a constant frequency. For the regulation loop power transistors, a resistor divider and an error
amplifier are used to keep the output voltage within the allowed limits. The error amplifier takes the feedback and
reference signals as inputs and generates the error voltage signal. The error voltage controls a driver that triggers the
gate voltage of the power transistor which modulates the current drive capability of the power amplifier. The modulated
transistor controls the charge transferred from the input to the output and therefore the regulation of the output is
realized. This regulation concept which is based on adjusting the amount of charge transferred, delivers the smallest
voltage ripple possible.
Figure 32. AS1302 - Functional Block Diagram
CFLY1
C1-
CFLY2
C2-
C1+
C2+
VOUT
VBATT
CBAT
Double-H Bridge
Topology
+
COUT
i(t)dt
∫
Vctrl
Vmode
Soft-
start
Mode
Select
Temp
State Machine
&
Ref
Bias
Control Logic
POR
CLK
EN
On
Off
AS1302
GND
Light/Heavy Load Monitor
To detetect the output current in the 2:3 and in the 1:2 mode, a current sense is used. The device switches to a lower
switching frequency (49kHz typ), due to a detected light-load condition. With this frequency an excellent light-load
efficiency is achieved and no audible noise is generated. If the load is increasing (typically more than 3mA), the device
operates at 1.2MHz.
www.austriamicrosystems.com/DC-DC_Step-Up/AS1302
Revision 1.03
10 - 18
AMSCO [ AMS(艾迈斯) ]
