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PDF RT9201 Data sheet ( Hoja de datos )
| Número de pieza | RT9201 | |
| Descripción | High Efficiency PWM Step-Down DC-DC Converter | |
| Fabricantes | Richtek Technology | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de RT9201 (archivo pdf) en la parte inferior de esta página. Total 13 Páginas | ||
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Preliminary
RT9201
High Efficiency PWM Step-Down DC-DC Converter
General Description
The RT9201 is a high-efficiency pulse-width-modulated
(PWM) step-down DC-DC converter. Capable of delivering
600mA output current over a wide input voltage range
from 2.5 to 5.5V, the RT9201 is ideally suited for portable
electronic devices that are powered from 1-cell Li-ion
battery or from other power sources within the range such
as cellular phones, PDAs and handy-terminals.
Four operational modes are available: PWM, PSM, Low-
Dropout and shut-down modes. Internal synchronous
rectifier with low RDS(ON) dramatically reduces conduction
loss at PWM mode. No external Schottky diode is
required in practical application. The RT9201 auto-
matically turns off the synchronous rectifier while the
inductor current is low and enters discontinuous PWM
mode. This can increase efficiency at light load condition.
The RT9201 enters PSM (pulse-skipping mode) at
extremely light load condition. The equivalent switching
frequency is reduced to increase the efficiency in PSM.
The RT9201 enters Low-Dropout mode when normal
PWM cannot provide regulated output voltage by
continuously turning on the upper P-MOSFET. RT9201
enters shut-down mode and consumes less than 0.1µA
when EN pin is pulled low.
The switching ripple is easily smoothed-out by small
package filtering elements due to a fixed operation
frequency of 800kHz. This along with small DFN package
provides small PCB area application. Other features
include soft start, 0.8V internal reference voltage with
1% accuracy, over temperature protection, and over
current protection.
Marking Information
For marking information, contact our sales representative
omdirectly or through a RichTek distributor located in your
.carea, otherwise visit our website for detail.
www.datasheet4uDS9201-04 August 2004
Features
l +2.5V to +5.5V Input Range
l Adjustable Output From 0.85V to VIN
l 600mA Output Current
l 95% Efficiency
l No Schottky Diode Required
l 85µA Quiescent Current
l 100% Duty Cycle in Low-Dropout Mode
l 800kHz Fixed-Frequency PWM Operation
l Pulse-skipping Mode Operation During Light Ioad
Applications
l Cellular Telephones
l Wireless Modems
l Personal Information Appliances
l Portable Instruments
l Distributed Power Systems
l Battery-Powered Equipment
(1 Li-Ion or 3 NiMH/NiCd)
Pin Configurations
(TOP VIEW)
EN 1
SS 2
FB 3
NC 4
GND 5
GND
10 NC
9 VDD
8 PVDD
7 LX
PGND
DFN-10L 3x3
Ordering Information
RT9201
Package Type
QV : DFN-10L 3x3 (V-Type)
Operating Temperature Range
P : Pb Free with Commercial Standard
www.richtek.com
1
1 page  
Preliminary
RT9201
Note 1. Stresses listed as the above "Absolute Maximum Ratings" may cause permanent damage to the device. These are for
stress ratings. Functional operation of the device at these or any other conditions beyond those indicated in the operational
sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may
remain possibility to affect device reliability.
Note 2. Devices are ESD sensitive. Handling precaution recommended.
Note 3. The device is not guaranteed to function outside its operating conditions.
Note 4. Guarantee the VOUT range from 0.85V to VIN base on VOUT>0.3VIN.
DS9201-04 August 2004
www.richtek.com
5
5 Page 
Preliminary
RT9201
4
VLX 2
(V)
0
Sub-Harmonic at Boundary
Condition
100
VOUT
(mV) 0
-100
VIN = 3.8V, VOUT = 3.3V
IOUT = 600mA, COUT = 100uF
Time (10µs/Div)
Figure 1
BouMndina.rIynpouf tPVWolMtagaendvsL.oOwu-tDpruotpCouurtreMnotde
5.50
5.00 PWM Mode
4.50
4.00
VOUT = 3.3V
3.50
3.00
2.50
VOUT = 2.5V
VOUT = 1.8V
2.00
Low Dropout Mode
1.50
1.00
0
100 200 300 400 500 600 700
OutpuItOCUTur(rmeAnt) (mA)
Figure 2
Over Current Protection
The RT9201 continuously monitors the inductor current
by sensing the voltage across the PMOSFET when it
turns on. When the inductor current is higher than current
limit threshold (1A typical), OCP activates and forces the
PMOSFET turning off to limit inductor current cycle by
cycle.
The current limit is set to 50% level of normal condition
when the output voltage is lower than its 50% normal
level. This can minimize the power loss and protect the
device when over current or output short circuit occurs.
Once output voltage drops below to its 50% normal level
DS9201-04 August 2004
due to over current or short circuit, it can build up only
when output current is lower 50% of normal current limit
threshold.
Output Voltage Setting and Feedback Network
The output voltage can be set from VREF to VIN by a
voltage divider as:
VOUT
=
VREF
×
RF1 + RF2
RF2
The internal VREF is 0.8V with 1% accuracy. In practical
application, keep RF2 = 390kΩ and CF2 = 10pF
respectively and choose appropriate RF1 and CF1
according to the required output voltage. Make sure that
the product of RF1 and CF1 is about 8200kΩ-pF. The
following table shows recommended feedback network
as well as inductor for some typical output voltages.
Table 1. Component Selection for Typical Application
VOUT
(V)
RF1
(Ω)
CF1
(pF)
RF2
(Ω)
CF2 LX CSS
(pF) (µH) (pF)
0.85 24k 330 390k 10 4.7 330
1.5 343k
2.5 820k
22 390k 10
10 390k 10
6.8 470
10 680
3.3 1.2M 5.6 390k 10 10 1000
Inductor Selection
The output inductor is suggested as the above table for
optimal performance. Make sure that the inductor will
not saturate over the operation conditions including
temperature range, input voltage range, and maximum
output current. If possible, choose an inductor with rated
current higher than 1A so that it will not saturate even
under circuit condition.
Input Capacitor Selection
The input capacitor can filter the input peak current and
noise at input voltage source. The capacitor with low ESR
(effective series resistance) provides the small drop
voltage to stabilize the input voltage during the transient
loading. For input capacitor selection, the ceramic
capacitors larger than 10µF is recommend. The capacitor
must conform to the RMS current requirement. The
maximum RMS ripple current is calculated as:
IRMS = IOUT(MAX)
VOUT (VIN − VOUT )
VIN
www.richtek.com
11
11 Page | ||
| Páginas | Total 13 Páginas | |
| PDF Descargar | [ Datasheet RT9201.PDF ] | |
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