A7506
AiT Semiconductor Inc.
www.ait-ic.com
DC-DC CONVERTER BOOST(STEP-UP)
1.2MHz CONSTANT FREQUENCY SYNCHRONUS
Current Sensing: A signal representing NMOS switch current is summed with the slope compensator. The
summed signal is compared to the error amplifier output to provide a peak current control command for the
PWM. Peak switch current is limited to approximately 850mAindependent of input or output voltage. The
current signal is blanked for 40ns to enhance noise rejection.
Zero Current Comparator: The zero current comparator monitors the inductor current to the output and shuts
off the synchronous rectifier once this current reduces to approximately 20mA. This prevents the inductor
current from reversing in polarity improving efficiency at light loads.
Anti-ringing Control: The anti-ringing control circuitry pre-vents high frequency ringing of the SW pin as the
inductor current goes to zero by damping the resonant circuit formed by L and CSW (capacitance on SW pin).
Pulse Skipping Mode
At very light load, the A7506 automatically switches into Pulse Skipping Mode to improve efficiency. During
this mode, the PWM control will skip some pulses to maintain regulation. If the load increases and the output
voltage drops, the device will automatically switch back to normal PWM mode and maintain regulation.
Device Shutdown
When SHDN is set logic high, the A7506 is put into operation. If SHDN is set logic low, the device is put into
shutdown mode and consumes lower than 1µA current. After start-up timing, the internal circuitry is supplied
by VOUT, however, if shutdown mode is enabled, the internal circuitry will be supplied by battery again.
Setting the Output Voltage
An external resistor divider is used to set the output voltage. The output voltage of the switching regulator
(VOUT) is determined by the following equation:
R1
R2
1+
VOUT = 1.23V x
Table 1. Resistor selection for output voltage setting
VOUT
3.3V
5.0V
R1(Ω)
1.02M
1.02M
R2(Ω)
604k
332k
REV1.1
- APR 2009 RELEASED, MAY 2017 UPDATED -
- 9 -
AITSEMI [ AiT Semiconductor ]
