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PDF BD3550HFN Data sheet ( Hoja de datos )
| Número de pieza | BD3550HFN | |
| Descripción | Ultra Low Dropout Linear Regulators | |
| Fabricantes | ROHM Semiconductor | |
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TECHNICAL NOTE
High-performance Regulator IC Series for PCs
Ultra Low Dropout
Linear Regulators for PC
BD3550HFN, BD3551HFN, BD3552HFN
(0.5～2.0A)
● Description
BD3550HFN,BD3551HFN,BD3552HFN ultra low-dropout linear chipset regulator operates from a very low input supply, and
offers ideal performance in low input voltage to low output voltage applications. It incorporates a built-in N-MOSFET power
transistor to minimize the input-to-output voltage differential to the ON resistance (RON=100mΩ <BD3552HFN>) level. By
lowering the dropout voltage in this way, the regulator realizes high current output (Iomax=2.0A <BD3552HFN>) with
reduced conversion loss, and thereby obviates the switching regulator and its power transistor, choke coil, and rectifier
diode. Thus, BD3550HFN,BD3551HFN,BD3552HFN is designed to enable significant package profile downsizing and cost
reduction. An external resistor allows the entire range of output voltage configurations between 0.65 and 2.7V, while the
NRCS (soft start) function enables a controlled output voltage ramp-up, which can be programmed to whatever power
supply sequence is required.
● Features
1) Internal high-precision reference voltage circuit(0.65V±1%)
2) Built-in VCC undervoltage lockout circuit
3) NRCS (soft start) function reduces the magnitude of in-rush current
4) Internal Nch MOSFET driver offers low ON resistance (100mΩ <BD3552HFN typ>)
5) Built-in current limit circuit
6) Built-in thermal shutdown (TSD) circuit
7) Variable output (0.65～2.7V)
8) Small package HSON8 : 2.9×3×0.6(mm)
9) Tracking function
● Applications
Notebook computers, Desktop computers, LCD-TV, DVD, Digital appliances
● Line-up
It is available to select power supply voltage and maximum output voltage.
Maximum Output Voltage
0.5A
1.0A
2.0A
Package
HSON8
Vcc=5V
BD3550HFN
BD3551HFN
BD3552HFN
Oct. 2008
1 page  
●Reference Data(BD3552HFN)
Vo
50mV/div
26mV
Vo
50mV/div
89mV
Vo
50mV/div
117mV
Io
2.0A/div
2.0A
Io
2.0A/div
2.0A
Io
2.0A/div
2.0A
Io=0A→1A/μsec t(10μsec/div)
Fig.13 Transient Response
(0→2.0A)
Co=100μF, Cfb=1000pF
Io=0A→1A/μsec t(10μsec/div)
Fig.14 Transient Response
(0→2.0A)
Co=47μF, Cfb=1000pF
Io=0A→1A/μsec t(10μsec/div)
Fig.15 Transient Response
(0→2.0A)
Co=22μF, Cfb=1000pF
Vo
50mV/div
54mV
Vo
50mV/div
83mV
Vo
50mV/div
117mV
Io
2.0A/div
2.0A
Io
2.0A/div
2.0A
Io
2.0A/div
2.0A
Io=1A→0A/μsec t(100μsec/div)
Fig.16 Transient Response
(2.0→0A)
Co=100μF, Cfb=1000pF
Io=1A→0A/μsec t(100μsec/div)
Fig.17 Transient Response
(2.0→0A)
Co=47μF, Cfb=1000pF
Io=1A→0A/μsec t(100μsec/div)
Fig.18 Transient Response
(2.0→0A)
Co=22μF, Cfb=1000pF
●Reference Data(BD3551HFN)
Ven
2V/div
VNRCS
2V/div
Vo
1V/div
t(200μsec/div)
Fig.19 Waveform at output
start
Ven
2V/div
VNRCS
2V/div
Vo
1V/div
t(2msec/div)
Fig.20 Waveform at output OFF
VCC
Ven
VIN
Vo
VCC→VIN→Ven
Fig.21 Input sequence
VCC
Ven
VIN
Vo
VIN→VCC→Ven
Fig.22 Input sequence
VCC
Ven
VIN
Vo
Ven→VCC→VIN
Fig.23 Input sequence
VCC
Ven
VIN
Vo
VCC→Ven→VIN
Fig.24 Input sequence
5/16
5 Page 
●Recommended Circuit Example
VCC
EN
1
C1
2
R4
3
4
VIN C2
8
GND
7
6 R1
C4
5 R2
FB
C5
VOUT1(1.2V)
C3
Component
R1/R2
C3
C1
C2
C4
C5
R4
Recommended
Value
3.9k/3.3k
22μF
1μF
22μF
0.01μF
-
Several kΩ
～several 10kΩ
Programming Notes and Precautions
IC output voltage can be set with a configuration formula using the values for the internal
reference output voltage (VFB)and the output voltage resistors (R1, R2). Select resistance
values that will avoid the impact of the VREF current (±100nA). The recommended total
resistance value is 10KΩ.
To assure output voltage stability, please be certain the Vo1, Vo2, and Vo3 pins and the
GND pins are connected. 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 (VCC) input pins. If the impedance of this power supply were to increase, input voltage
(VCC) could become unstable, leading to oscillation or lowered ripple rejection function.
While a low-ESR 1 μ F 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.
Input capacitors reduce the output impedance of the voltage supply source connected to
the (VIN) input pins. If the impedance of this power supply were to increase, input voltage
(VIN) could become unstable, leading to oscillation or lowered ripple rejection function.
While a low-ESR 22 μ F 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 C3 capacitor causes, or may cause, oscillation. It
provides more precise internal phase correction.
It is recommended that a resistance (several kΩ to several 10kΩ) be put in R4, in case
negative voltage is applied in EN pin.
11/16
11 Page | ||
| Páginas | Total 19 Páginas | |
| PDF Descargar | [ Datasheet BD3550HFN.PDF ] | |
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