CXSU63133 is a compact, PFM mode, and step-up DC-DC converter with low quiescent current. The inter- nal synchronous rectifier reduces cost and PCB space by eliminating the need for an external

五,产品封装图 (Package)

六.电路原理图</span>gHd嘉泰姆

七</span>,功能概述gHd嘉泰姆

Inductor Selection
The inductor value determines the inductor ripple current
and affects the load transient response. It is recom-
mended to select the boost inductor in order to keep the
maximum peak inductor current below the current limit
threshold of the power switch. For example, the current
limit threshold of the CXSU63133’s switch is 600mA. For
choosing an inductor which has peak current passed,
firstly, it is necessary to consider the output load (IOUT),
input (VIN), and output voltage (VOUT). Secondly, the de-
sired current ripple in the inductor also needed to be
taken into account. The current was calculated in “Output
Capacitor Selection”. Since the output ripple is the prod-
uct of the peak inductor current and the output capacitor
ESR, the larger inductor value reduces the inductor cur-
rent ripple and output voltage ripple but typically offers a
larger physical size.gHd嘉泰姆

Control Scheme
The converter monitors the output voltage. When the in-
ternal feedback voltage falls below the reference voltage,
the main switch turns on and the inductor current ramps
up. The main switch turns off when the current reaches
the peak current limit of typical 600mA. The second crite-
rion that turns off the switch is the maximum on-time of
4μs (typical). As the main switch is turned off, the syn-
chronous switch is turned on and delivers the current to
the output. The main switch remains off for a minimum of
900ns (typical), or until the internal feedback voltage drops
below the reference voltage. By the control scheme with
low quiescent current of 11μA (typical), the converter gets
high efficiency over a wide load range. 
Start-Up
A startup oscillator circuit is integrated in the CXSU63133.
When the power is applied to the device, the circuit pumps
the output voltage high. Once the output voltage reaches
1.4V (typ), the main DC-DC circuitry turns on and boosts
the output voltage to the final regulation point.
Synchronous Rectification
The internal synchronous rectifier eliminates the need
for an external Schottky diode, thus, reducing cost and
board space. During the cycle off-time, the P-channel
MOSFET turns on and shunts the MOSFET body diode.
As a result, the synchronous rectifier significantly improves
efficiency without the addition of an external component.
Conversion efficiency can be as high as 92%. 
Over-Temperature Protection
The over-temperature circuit limits the junction tempera-
ture of the CXSU63133. When the junction temperature ex-
ceeds 150°C, a thermal sensor turns off the power
MOSFETs, allowing the devices to cool. The thermal sen-
sor allows the converter to start a start-up process and
regulate the output voltage again after the junction tem-
perature cools by 40°C. The OTP is designed with a 40°C
hysteresis to lower the average TJ during continuous ther-
mal overload conditions, increasing lifetime of the device.gHd嘉泰姆

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