AAT3183_08 Datasheet, PDF (10/15 Pages) Advanced Analogic Technologies – 300mA Inductorless Step-Down Converter

ChargePump^TM
Therefore, the AAT3183 provides a 100% efficiency
improvement over conventional LDO regulators, as illus-
trated in Figure 2.
90
80
AAT3183
70
60
50
40
LDO
30
20
10
0
50
100
150
200
250
300
Output Current (mA)
Figure 2: AAT3183 Efficiency Comparison vs. LDO.
Under-Voltage Lockout
Under-voltage lockout (UVLO) circuitry monitors the
input voltage (V_IN) and ensures that the device will
remain in standby (V_OUT = 0V) until a valid V_IN is present.
When V_IN is less than 1.5V (typical), the input current is
less than 1μA and the output voltage (V_OUT) remains at
0V, regardless of the status of the enable pin (EN).
Typically, the UVLO turn-on threshold is 150mV greater
than the UVLO turn-off threshold. UVLO hysteresis mini-
mizes spurious under-voltage detection and eliminates
output glitches.
Shutdown and Soft-Start
The AAT3183 offers an enable pin (EN). When V_EN is
below 0.4V (maximum), the device is in standby (shut-
down) mode and draws less than 1μA of input current.
The output will remain at 0V when EN voltage is low (V_EN
PRODUCT DATASHEET
AAT3183
300mA Inductorless Step-Down Converter
≤ 0.4V). When EN is connected to a voltage greater than
1.4V (minimum), the AAT3183 will initiate soft-start and
resume normal operation.
The product features built-in soft-start circuitry to reduce
inrush current and eliminate output voltage overshoot.
The soft-start circuitry is enabled when input UVLO con-
ditions are satisfied and the EN voltage is high (V_EN ≥
1.4V). If EN is tied to IN, the soft start is initiated when
UVLO conditions are satisfied. The soft-start circuitry
ramps up the output voltage in a controlled manner and
minimizes output overshoot. Start-up time from EN
positive transitioning (V_EN: ≤0.4V to ≥1.4V) to output
(V_OUT) in regulation is 100μs (typical).
Thermal and Short-Circuit Protection
High device temperature may result at elevated ambient
temperatures or in cases where high output current
causes self heating of the device. The device will disable
all switching of the charge pump when the internal junc-
tion temperature exceeds 150°C (typical). The device
will restart and enable the soft-start sequence when the
temperature is reduced 15°C. This hysteresis ensures
that the absolute device temperature is maintained
below the over-temperature threshold and protects the
device from damage.
In the event of a short circuit, an internal current limit is
activated and limits the output current to 1A (typical).
This current is maintained until the output fault condition
is removed or device over-temperature is reached.
Under sustained short-circuit conditions, the device will
typically reach over-temperature and latch off. The
device will cool down after a short period and continue
to oscillate between active and over-temperature protec-
tion states until the fault is removed. Under these worst
case conditions, the device average junction tempera-
ture will be less than 150°C.
10
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