Boost Converter. RT9277D Datasheet

RT9277D Converter. Datasheet pdf. Equivalent

RT9277D Datasheet
Recommendation RT9277D Datasheet
Part RT9277D
Description Low Noise Boost Converter
Feature RT9277D; RT9277C/D High Performance, Low Noise Boost Converter General Description Features The RT9277C/D.
Manufacture Richtek
Datasheet
Download RT9277D Datasheet




Richtek RT9277D
RT9277C/D
High Performance, Low Noise Boost Converter
General Description
Features
The RT9277C/D is a high performance, low noise, fixed
frequency step up DC-DC Converter. The RT9277C/D
converters input voltage ranging 2.5V to 5.5V into output
voltage up to 16V. Current mode control with external
compensation network makes it easy to stabilize the
system and keep maximum flexibility. Soft start function
minimizes impact on the input power system. Internal power
MOSFET with very low RDS(ON) provides high efficiency.
The RT9277C/D with 640kHz and 1.2MHz operation
frequency options provide flexibiltity of minimum output
inductor size, maximum efficiency and low BOM cost.
z Efficiency up to 90%
z VIN Operating Range : 2.5V to 5.5V
z 1.6A, 0.2Ω, 16V Internal Power MOSFET
z 640kHz and 1.2MHz Operation Frequency
z External Compensation
z Internal/External Programmable Soft Start
z Small MSOP8 Package
z OCP and OTP Function are Included
z RoHS Compliant and Halogen Free
Applications
The RT9277C/D also provides comprehensive protection
functions such as UVLO, OCP and OTP.
Ordering Information
RT9277C/D
Package Type
F : MSOP-8
QW : WDFN-8L 3x3 (W-Type)
Lead Plating System
G : Green (Halogen Free and Pb Free)
Note :
Soft Start Function
C : External Programmable
D : Internal Programmable
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.
z TFT LCD panel
z OLEDDisplay
z PCMCIA Cards
z Portable Device
Pin Configurations
(TOP VIEW)
COMP
FB
EN
GND
8
27
36
45
MSOP-8
SS
FREQ
VIN
LX
COMP 1
FB 2
EN 3
GND 4
8 SS
7 FREQ
6 VIN
9 5 LX
RT9277C
WDFN-8L 3x3
Marking Information
For marking information, contact our sales representative
directly or through a Richtek distributor located in your
area.
COMP
FB
EN
GND
8
27
36
45
MSOP-8
NC
FREQ
VIN
LX
COMP 1
FB 2
EN 3
GND 4
8 NC
7 FREQ
6 VIN
9 5 LX
RT9277D
WDFN-8L 3x3
DS9277C/D-01 April 2011
www.richtek.com
1



Richtek RT9277D
RT9277C/D
Typical Application Circuit
VIN
2.5V to 5.5V
C1
L1 D1
5 LX
GND 4
6 VIN
EN 3
7 FREQ FB 2
8 SS COMP 1
C5 RT9277C
Chip Enable
C2
R3
C4 C3
VOUT
R1
R2
Figure 1
VIN
2.5V to 5.5V
C1
Chip Enable
L1 D1
5 LX
6 VIN
GND 4
EN 3
VOUT
C2
R1
7 FREQ FB 2
8 NC COMP 1
R3
RT9277D
C4 C3
R2
Figure 2
Table 1. Recommended Components
Symbol
(unit)
VIN VOUT FOSC
(V) (V) (Hz)
Application 1 3.3
9 1.2M
Application 2 3.3
12 1.2M
Application 3 3.3
12 640K
C1
(μF)
10
10
10
L1
(μH)
4.7(TDK SLF6028)
4.7(TDK SLF6028)
10(TDK SLF6028)
C2
(μF)
33 (ceramic)
33 (ceramic)
33 (ceramic)
R3
(k)
82
180
120
C3
(pF)
82 0
68 0
1200
C4
(pF)
10
22
22
Function Block Diagram
www.richtek.com
2
EN
COMP
FB
FREQ
LX
VIN Protection
VFB
1.24V
Error
Amplifier
-
+
Summing
Comparator
-
+
5µA
Oscillator
Slope
Compen-
sation
Clock
4µA
Soft-
Start
Control
and
Driver
Logic
N
Current
Sense
RT9277C
VIN
SS
LX
GND
DS9277C/D-01 April 2011



Richtek RT9277D
RT9277C/D
EN
COMP
FB
FREQ
LX
VIN
VFB
Protection
Internal
Soft-Start
1.24V
Error
Amplifier
-
+
Summing
Comparator
-
+
5µA
Oscillator
Slope
Compen-
sation
Clock
Control
and
Driver
Logic
Current
Sense
N
VIN
LX
GND
RT9277D
Operation
The RT9277C/D is a high efficiency step-up Boost converter
with a fixed-frequency, current-mode PWM architecture.
It performs fast transient response and low noise operation
with appropriate component selection. The output voltage
is regulated through a feedback control consisting of an
error amplifier, a summing comparator, and several control
signal generators (as shown in function block diagram).
The feedback reference voltage is 1.24V. The error amplifier
varies the COMP voltage by sensing the FB pin. The slope
compensation signal summed with the current -sense
signal will be compared with the COMP voltage through
the summing comparator to determine the current trip point
and duty cycle.
Soft-Start
The RT9277C provides programmable soft-start function.
When the EN pin is connected to high, a 4μA constant
current is sourced to charge an external capacitor. The
voltage rate of rise on the COMP pin is limited during the
charging period, and so is the peak inductor current.
When the EN pin is connected to GND, the external
capacitor will be discharged to ground for the next time
soft-start.
Current Limitation
The switch current is monitored to limit the value not to
exceed 1.6A typically. When the switch current reaches
1.6A, the output voltage will be pulled down to limit the
total output power to protect the power switch and external
components.
Shutdown
Connect the EN to GND to turn the RT9277C/D off and
reduce the supply current to 0.1μA. In this operation, the
output voltage is the value of VIN to subtract the forward
voltage of catch diode.
Frequency Selection
The switching frequency of RT9277C/D can be selected to
operate at either 640kHz or 1.2MHz. When the FREQ pin
is connected to GND for 640kHz operation, and connected
to VIN for 1.2MHz operation. FREQ is preset to 640kHz
operation for allowing the FREQ pin unconnected.
DS9277C/D-01 April 2011
www.richtek.com
3







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