BD3522EFV_08 Datasheet, PDF (14/21 Pages) Rohm – Ultra Low Dropout Linear Regulators(4A) for Desktop PC

●Recommended Circuit Example (BD3522EFV)
R15
R14
VIN C20
C12 EN
C13
20 19 18 17 16 15 14 13 12 11
V_IN V_IN V_IN V_IN V_IN V_IN VD SCP EN Vcc
C11 Vcc
Vo Vo Vo Vo Vo Vo FB NRCS GND GND
1
2
3
4
5
6
7
8
9 10
C8
R6
R7
C1
C6
Component
R6/R7
Recommended
Value
3.3k /3.9k
C1
22μF
C11/C20 1μF/10μF
C8
0.01μF
C6
1000pF
C13
330pF
Programming Notes and Precautions
IC output voltage can be set with a configuration formula V_FB×(R6+R7)/R7 using the
values for the internal reference output voltage (V_FB) and the output voltage resistors (R6,
R7). Select resistance values that will avoid the impact of the FB bias current (±100nA).
The recommended total resistance value is 10KΩ.
To assure output voltage stability, please be certain the output capacitors are connected
between Vo pin and GND. Output capacitors play a role in loop gain phase compensation
and in mitigating output fluctuation during rapid changes in load level. Insufficient
capacitance may cause oscillation, while high equivalent series reisistance (ESR) will
exacerbate output voltage fluctuation under rapid load change conditions. While a 22μF
ceramic capacitor is recomended, actual stability is highly dependent on temperature and
load conditions. Also, note that connecting different types of capacitors in series may result
in insufficient total phase compensation, thus causing oscillation. In light of this information,
please confirm operation across a variety of temperature and load conditions.
Input capacitors reduce the output impedance of the voltage supply source connected to
the (V_CC, V_IN) input pins. If the impedance of this power supply were to increase, input
voltage (V_CC, V_IN) could become unstable, leading to oscillation or lowered ripple rejection
function. While a low-ESR 1μF/10μF capacitor with minimal susceptibility to temperature
is recommended, stability is highly dependent on the input power supply characteristics
and the substrate wiring pattern. In light of this information, please confirm operation
across a variety of temperature and load conditions.
The Non Rush Current on Startup (NRCS) function is built into the IC to prevent rush
current from going through the load (VIN to VO) and impacting output capacitors at power
supply start-up. Constant current comes from the NRCS pin when EN is HIGH or the
UVLO function is deactivated. The temporary reference voltage is proportionate to time,
due to the current charge of the NRCS pin capacitor, and output voltage start-up is
proportionate to this reference voltage. Capacitors with low susceptibility to temperature
are recommended, in order to assure a stable soft-start time.
This component is employed when the C16 capacitor causes, or may cause, oscillation. It
provides more precise internal phase correction.
The Short Circuit Protection (SCP) function and the Thermal Shut Down (TSD) function
are built into the IC. Constant current comes from the SCP pin when SCP function or TSD
function is operated. (SCP:4μA, TSD:20μA TYP.) The voltage occurred in SCP pin by
this current overstep the threshold voltage, the status of voltage becomes OFF. Capacitors
with low susceptibility to temperature (330pF or more) are recommended, in order to
assure a stable TSD delay setting time. In light of this information, please confirm the
capacitor value to prevent startup defective.
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