A7116
AiT Semiconductor Inc.
www.ait-ic.com
DC-DC CONVERTER/ BUCK (STEP-DOWN)
1.5MHz, 700mA SYNCHRONOUS WITH LOW QUIESCENT CURRENT
DETAILED INFORMATION
Operation
A7116 is a monolithic switching mode Step-Down DC-DC converter. It utilizes internal MOSFETs to achieve
high efficiency and can generate very low output voltage by using internal reference at 0.6V. It operates at a
fixed switching frequency, and uses the slope compensated current mode architecture. This Step-Down
DC-DC Converter supplies 700mA output current at VOUT = 1.8V with input voltage range from 2.5V to 6.5V.
Current Mode PWM Control
Slope compensated current mode PWM control provides stable switching and cycle-by-cycle current limit for
excellent load and line responses and protection of the internal main switch (P-Ch MOSFET) and
synchronous rectifier (N-CH MOSFET). During normal operation, the internal P-Ch MOSFET is turned on for
a certain time to ramp the inductor current at each rising edge of the internal oscillator, and switched off when
the peak inductor current is above the error voltage. The current comparator, ICOMP, limits the peak inductor
current. When the main switch is off, the synchronous rectifier will be turned on immediately and stay on
until either the inductor current starts to reverse, as indicated by the current reversal comparator, IZERO, or the
beginning of the next clock cycle. The OVDET comparator controls output transient overshoots by turning the
main switch off and keeping it off until the fault is no longer present.
Power Saving Mode Operation
At very light loads, the A7116 automatically enters Power Saving Mode. In power saving mode at light load,
a control circuit puts most of the circuit into sleep in order to reduce quiescent current and improve efficiency
at light load. When the output voltage drops to certain threshold, the control circuit turns back on the
oscillator and the PWM control loop, boosting output backup. When an upper threshold is reached, the control
circuit again puts most of circuit into sleep, reducing quiescent current. During Power Saving Mode operation,
the converter positions the output voltage slightly higher than the nominal output voltage during PWM
operation, allowing additional headroom for voltage drop during a load transient from light to heavy load.
While the power saving mode improves light load efficiency, however, with the turning on and off, the noise or
ripple voltage is larger than that in the PWM Mode.
REV1.2
- JAN 2009 RELEASED, MAY 2016 UPDATED -
- 8 -
AITSEMI [ AiT Semiconductor ]
