AS1326
Data Sheet - Detailed Description
Synchronized-PWM Operation
In PWM mode the AS1326A/AS1326B can be synchronized with an external clock (500kHz to 1.2MHz) by applying an
external clock signal to pin CLK/SEL. This synchronization will minimize interference in wireless applications since the
operating frequency can be set to a preferred value. The synchronous rectifier is active during synchronized-PWM
operation.
Synchronous Rectifier
The AS1326A/AS1326B feature an integrated, P-channel synchronous rectifier for enhanced efficiency operation. Syn-
chronous rectification provides 5% improved efficiency over similar non-synchronous boost regulators.
In PWM mode, the synchronous rectifier is turned on during the second half of each switching cycle. In low-power
mode, an internal comparator turns on the synchronous rectifier when the voltage at LX exceeds the boost regulator
output.
Note: While operating with output voltages greater than 4V, an external 0.5A Schottky diode must be connected in
parallel with the P-channel synchronous rectifier.
Low-Voltage Startup Oscillator
The AS1326A/AS1326B contain a CMOS, low-voltage startup oscillator for a 1.1V guaranteed minimum startup input
voltage. At startup, the low-voltage oscillator switches on the N-channel MOSFET until the output voltage reaches
2.15V. With output voltages > 2.15V, the boost-converter feedback and control circuitry are acitvated.
When the AS1326A/AS1326B is in regulation, it can operate down to 0.7V input since internal power for the device is
bootstrapped from the output through pin OUT.
Caution: Do not apply full load until the output > 2.3V.
Shutdown
The AS1326A/AS1326B feature an integrated shutdown mode that reduces quiescent current to 0.1µA. During shut-
down mode (ONN = 1 on AS1326A, ON = 0 on AS1326B), the internal reference and feedback/control circuitry are dis-
abled.
Note: During shutdown, the output voltage is one diode drop below the input voltage.
Reference
The AS1326A/AS1326B contain an internal reference (1.250V ±1%). A 10nF ceramic bypass capacitor must be con-
nected between pins REF and GND. REF can source up to 50µA of external load current.
Note: The bypass capacitor must be placed within 5mm (0.2”) of pin REF.
www.austriamicrosystems.com
Revision 1.02
10 - 18
AMSCO [ AMS(艾迈斯) ]
