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PDF RT8553A Data sheet ( Hoja de datos )
| Número de pieza | RT8553A | |
| Descripción | Dual-Output Synchronous DC/DC Converter | |
| Fabricantes | Richtek | |
| Logotipo |  |
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®
RT8553A
Dual-Output Synchronous DC/DC Converter
General Description
The RT8553A is a dual-output DC/DC converter which is
designed to provide the power for consumer products. It
integrates a Boost converter and an inverting-Boost
converter for enhancing the overall system efficiency of
battery powered products. The RT8553A operates in
Forced CCM mode for light load and heavy load condition.
The high frequency allows for reduction of external
components. In shutdown mode, the RT8553A consumes
less than 1μA current. The RT8553A provides soft-start,
OCP, OTP, OVP and UVLO function. The RT8553A is
available in the tiny UDFN-12L 3x3 package to achieve
best solution for saving PCB space and total BOM cost
saving considerations.
Ordering Information
RT8553A
Package Type
QU : UDFN-12L 3x3 (U-Type)
Lead Plating System
G : Green (Halogen Free and Pb Free)
Note :
Richtek products are :
RoHS compliant and compatible with the current require-
ments of IPC/JEDEC J-STD-020.
Suitable for use in SnPb or Pb-free soldering processes.
Features
Boost Converter to Supply Positive Voltage from
4.6V to 5.4V Through External Feedback Resistors
Buck-Boost Converter to Supply Negative Voltage
from −4.6V to −5.4V Through External Feedback
Resistors
Maximum Output Current up to 200mA
Typical Efficiency : 85%
PWM Mode @ 1.5MHz Switching Frequency
High Output Voltage Accuracy
Excellent Line and Load Transient
Excellent Line and Load Regulation
Soft-Start to Limit Inrush Current
Over-Temperature Protection (OTP)
Over-Current Protection (OCP)
Over-Voltage Protection (OVP)
Low Quiescent Current < 1μA in Shutdown Mode
RoHS Compliant and Halogen Free
Applications
Cellular Phones
Digital Cameras
PDAs and Smart Phones
Probable Instruments
Simplified Application Circuit
L1
VIN
Enable
CIN1
CIN2
RT8553A
VINP
LX1
LX2
VINA
VOUT1
EN
GND
FB1
VOUT2
PGND
AGND
FB2
VREF
L2
VOUT1
R1 COUT1
R2
VOUT2
R3 COUT2
R4
Copyright ©2015 Richtek Technology Corporation. All rights reserved.
DS8553A-00 January 2015
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
1
1 page  
RT8553A
Parameter
Switching Frequency
Reference Voltage
Boost Maximum Duty
Inv erting-Boost Maximum
Duty
System Efficiency
Over-Temperature
Protection
Over-Temperature
Protection Hysteresis
Boost Converter
Positive Output Voltage
Range
Positive Output Voltage
Total Variation
Maximum Output Current
Feedback Voltage
of Boost Converter
Over Voltage
of Boost Converter
Load Transient
Static Line Regulation
Static Load Regulation
Boost Switching Current
Limit
N1 N-MOSFET
On-Resistance
P1 P-MOSFET
On-Resistance
Symbol
fSWPW M
VREF
D1MAX
D2MAX
ESYS
OTP
Test Conditions
FCCM Mode
VREF
Open Loop Condition
Open Loop Condition
IOUT1 = IOUT2 = 10mA to 30mA,
VOUT1 = 5V, VOUT2 = 5V
IOUT1 = IOUT2 = 30mA to 200mA,
VOUT1 = 5V, VOUT2 = 5V
OTPHYST
VOUT1
IO UT 1MA X
VFB1
VINA = VINP = 2.9V to 4.5V
IOUT1 = 5mA to 200mA
IOUT2 = No Load
VINA = VINP = 2.9V to 4.5V
VINA = VINP = 2.9V to 4.5V
VOVP1
IOUT1 = 3mA to 30mA and
IOUT1 = 30mA to 3mA,
TR = TF = 150s,
Output Variation respect to VOUT1
VOUT1LOAD_LT IOUT1 = 10mA to 100mA and
IOUT1 = 100mA to 10mA,
TR = TF = 150s,
Output Variation respect to VOUT1
VOUT1LINE_SL
VINA = VINP = 2.9V to 4.5V,
IOUT1 = 5mA, IOUT2 = No Load
VINA = VINP = 2.9V to 4.5V,
IOUT1 = 100mA, IOUT2 = No Load
IOUT1 = 5 to 100mA, IOUT2 = No Load,
VOUT 1LOAD_S L
VINA = VINP = 2.9V
IOUT1 = 5 to 100mA, IOUT2 = No Load,
VINA = VINP = 4.5V
ILX1 VINA = VINP = 2.9V to 4.35V
RDS(ON)1
VINA = VINP = 3.7V, ILX1 = 100mA
VINA = VINP = 3.7V, ILX1 = 100mA
Min
1.35
--
--
--
--
--
--
--
4.6
2
200
--
--
--
--
--
--
--
--
--
--
--
Typ Max Unit
1.5 1.65 MHz
1 -- V
85 -- %
85 -- %
80 --
85 --
%
140 -- C
15 -- C
5.0 5.4 V
-- 2 %
-- -- mA
1 -- V
6 -- V
±20 -- mV
±25 -- mV
0.5 --
0.5 --
0.5 --
0.5 --
1 --
0.2 --
0.3 --
%
%
A
Copyright ©2015 Richtek Technology Corporation. All rights reserved.
DS8553A-00 January 2015
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
5
5 Page 
Application Information
The RT8553A is a dual channel DC/DC converter capable
of generating both positive and negative outputs by external
feedback voltage-divider resistors from an input voltage
range of 2.5V to 4.5V. Each converter works independently
of one another and both outputs are separately controlled
by a fixed frequency Pulse-Width-Modulated (PWM)
regulator.
Soft-Start
The RT8553A employs a soft-start feature for both
converters to limit the inrush current and prevent input
voltage droop. When each converter is enabled, the
implemented switch current limit ramps up slowly to its
nominal programmed value in about 2ms for the Boost
converter and Buck-Boost converter.
Over-Voltage Protection (OVP)
The RT8553A has over-voltage circuit protection
mechanism which prevents feedback pin floating when the
IC is enabled. When output voltage exceeds OVP
threshold voltage, the IC would be clamped at fixed voltage
with minimum duty.
Over-Current Protection (OCP)
The RT8553A includes a current sensing circuitry which
monitors the inductor current during each charging cycle.
If the current value becomes greater than the current limit,
the converter will be shutdown and can only re-start normal
operation after triggering EN pin or re-power on again.
Over-Temperature Protection (OTP)
The RT8553A includes an Over-Temperature Protection
(OTP) feature to prevent the device from overheat due to
excessive power dissipation. The OTP function shuts down
all device operations when the junction temperature
exceeds 140°C. Once the junction temperature cools
down by approximately 15°C, the converter resumes
operation. To maintain continuous operation, prevent the
maximum junction temperature form rising above 125°C.
RT8553A
Under-Voltage Lockout (UVLO)
The Under-Voltage Lockout (UVLO) circuitry compares
the input voltage with the UVLO threshold to ensure that
the input voltage is high enough for reliable operation.
Once the input voltage exceeds the UVLO rising threshold
at 2.22V (typ.), start-up begins. A 40mV (typ.) hysteresis
is included to prevent supply transients from causing a
shutdown.
Positive Output Voltage Setting
The output voltage setting can be calculated according to
the following equation :
VOUT1
=
VFB1 1
R1
R2
where VFB1 is the reference voltage with a typical value of
1V.
Input Capacitor Selection
Input ceramic capacitors with 10μF capacitance are
suggested for the RT8553A applications. However, to
achieve best performance with the RT8553A, larger
capacitance can be used. For better voltage filtering, select
ceramic capacitors with low ESR, X5R and X7R types are
suitable because of their wider voltage and temperature
ranges.
Boost Inductor Selection
The inductance depends on the maximum input current.
As a general rule, the inductor ripple current range is 20%
to 40% of the maximum input current. If 40% is selected
as an example, the inductor ripple current can be
calculated according to the following equations :
IIN(MAX)
=
VOUT IOUT(MAX)
VIN
IL = 0.4 IIN(MAX)
where η is the efficiency of the converter, IIN(MAX) is the
maximum input current, and ΔIL is the inductor ripple
current. The input peak current can then be obtained by
adding the maximum input current with half of the inductor
ripple current as shown in the following equation :
Ipeak = 1.2 x IIN(MAX)
Copyright ©2015 Richtek Technology Corporation. All rights reserved.
DS8553A-00 January 2015
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
11
11 Page | ||
| Páginas | Total 15 Páginas | |
| PDF Descargar | [ Datasheet RT8553A.PDF ] | |
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