AiT Semiconductor Inc.
A7231A
DC-DC CONVERTER BUCK (STEP-DOWN)
500kHz, 3A, 16V SYNCHRONOUS
www.ait-ic.com
DETAILED INFORMATION
Internal Regulator
The A7231A is a current mode step down DC/DC converter that provides excellent transient response with no
extra external compensation components. This device contains an internal, low resistance, high voltage
power MOSFET, and operates at a high 500k operating frequency to ensure a compact, high efficiency
design with excellent AC and DC performance.
Error Amplifier
The error amplifier compares the FB pin voltage with the internal FB reference (VFB) and outputs a current
proportional to the difference between the two. This output current is then used to charge or discharge the
internal compensation network to form the COMP voltage, which is used to control the power MOSFET
current. The optimized internal compensation network minimizes the external component counts and
simplifies the control loop design.
Internal Soft-Start
The soft-start is important for many applications because it eliminates power-up initialization problems. The
controlled voltage ramp of the output also reduces peak inrush current during start-up, minimizing start-up
transient events to the input power bus.
Over-Current-Protection and Hiccup
The A7231A has a cycle-by-cycle over-current limit for when the inductor current peak value exceeds the set
current-limit threshold. First, when the output voltage drops until FB falls below the Under-Voltage (UV)
threshold (typically 140mV) to trigger a UV event, the A7231A enters hiccup mode to periodically restart the
part. This protection mode is especially useful when the output is dead-shorted to ground. This greatly
reduces the average short-circuit current to alleviate thermal issues and to protect the regulator. The A7231A
exits hiccup mode once the overcurrent condition is removed.
Startup and Shutdown
If both VIN and EN are higher than their appropriate thresholds, the chip starts. The reference block starts first,
generating stable reference voltage and currents, and then the internal regulator is enabled. The regulator
provides stable supply for the remaining circuitries. Three events can shut down the chip: EN low, VIN low
and thermal shutdown. In the shutdown procedure, the signaling path is first blocked to avoid any fault
triggering. The COMP voltage and the internal supply rail are then pulled down. The floating driver is not
subject to this shutdown command.
REV1.0
- MAY 2018 RELEASED -
- 9 -
AITSEMI [ AiT Semiconductor ]
