Preliminary
RT9262/A
High Efficiency, Low Supply Current, Step-up DC/DC Converter
General Description
The RT9262/A is a compact, high efficient, step-up
DC/DC converter with an adaptive current mode PWM
control loop, providing a stable and high efficient operation
over a wide range of load currents. It operates in both
continuous and discontinuous current modes in stable
waveforms without external compensation.
The low start-up input voltage below 1V makes
RT9262/A suitable for 1 to 4 battery cell applications
providing up to 400mA output current. The 550kHz high
switching rate minimized the size of external components.
Besides, the 17μA low quiescent current together with
high efficiency maintains long battery lifetime.
The 1.8V to 5V output voltage is set with 2 external
resistors. Both internal 2A switch and driver for driving
external power devices (NMOS or NPN) are provided.
A 300mA LDO is included in RT9262 to provide a
secondary low noise output as well as an output current
stop in the shutdown mode. Similarly, a 1.8V to 5V LDO
output voltage can be set with 2 external resistors. For
RT9262A, a low battery detector with 0.86V detection
voltage is included. RT9262/A are provided in SOP-8
packages.
Features
1.0V Low Start-up Input Voltage
High Supply Capability to Deliver 3.3V 100mA with
1V Input Voltage
17μA Quiescent (Switch-off) Supply Current
μ
90% Efficiency
550kHz Fixed Switching Rate
Providing Flexibility for Using Internal and External
Power Switches
Built-in 300mA LDO, also for the Zero-Output-
Current Shutdown Mode (RT9262)
Boost DC-DC Integrating LDO for Up-Down
Regulation (RT9262)
Built-in 0.86V Voltage Detector (RT9262A)
8-Pin SOP Package
RoHS Compliant and 100% Lead (Pb)-Free
Applications
PDA
Portable Instrument
Wireless Equipment
DSC
LCD Back Bias Circuit
RF-Tags
Ordering Information
RT9262/A
Package Type
S : SOP-8
Operating Temperature Range
P : Pb Free with Commercial Standard
G : Green (Halogen Free with Commer-
cial Standard)
Include Low Battery Detector
Include LDO
Pin Configurations
(TOP VIEW)
GND
EXT
LFB
LDO O
2
3
4
8
7
6
5
EN
LX
VDD
FB
RT9262CS
Note :
RichTek Pb-free and Green 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.
100%matte tin (Sn) plating.
GND
EXT
LBO
LBI
2
3
4
8
7
6
5
EN
LX
VDD
FB
RT9262ACS
SOP-8
DS9262/A-11 March 2007
www.richtek.com
1
RT9262/A
Functional Pin Description
Pin No.
RT9262
1
2
3
4
RT9262A
1
2
--
--
GND
EXT
LFB
LDOO
Ground
Pin Name
Preliminary
Pin Function
Output Pin for Driving External NMOS or NPN
When driving an NPN, a resistor should be added for limiting base current.
Feedback Pin of the Built-in LDO (Internal Vref = 0.86V)
Voltage Output Pin of the Built-in LDO
Drain Output Pin of the NMOS of the Built-in Low Voltage Detector
--
3
LBO
This pin will be internally pulled low when the voltage at LBI pin drops to
below 0.86V.
--
4
LBI
Input Pin of the Built-in Low Voltage Detector
Trip point = 0.86V
Feedback Input Pin
Internal reference voltage for the error amplifier is 1.25V.
Input Positive Power Pin of RT9262/A
Pin for Switching
Chip Enable Pin (Active High).
5
6
7
8
5
6
7
8
FB
VDD
LX
EN
Function Block Diagram
VDD
Q2
P MOS
LDO O
LFB
FB
1.25V
VDD
R2
Shut Down
EN
Q3
N MOS
Over Temp.
Detector
RT9262
-
+
EXT
LX
-
+
Loop Control Circuit
Q1
N MOS
R1
0.86V
VDD
GND
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4
DS9262/A-11 March 2007
Preliminary
VDD
LBI
LBO
Q2
N MOS
-
+
0.86V
EXT
LX
FB
1.25V
VDD
R2
Shut Down
EN
Q3
N MOS
Over Temp.
Detector
RT9262/A
RT9262A
-
+
Loop Control Circuit
Q1
N MOS
R1
GND
Absolute Maximum Ratings
Supply Voltage -----------------------------------------------------------------------------------------------------
−
0.3V to 7V
LX Pin Switch Voltage --------------------------------------------------------------------------------------------
−
0.3V to 7V
LDO Output Voltage ----------------------------------------------------------------------------------------------
−
0.3V to (V
DD
+ 0.3V)
Other I/O Pin Voltages -------------------------------------------------------------------------------------------
−
0.3V to (V
DD
+ 0.3V)
LX Pin Switch Current -------------------------------------------------------------------------------------------- 2.5A
EXT Pin Driver Current -------------------------------------------------------------------------------------------- 30mA
LBO Current -------------------------------------------------------------------------------------------------------- 30mA
Power Dissipation, P
D
@ T
A
= 25°C
SOP-8 ---------------------------------------------------------------------------------------------------------------- 0.625W
Package Thermal Resistance
SOP-8,
θ
JA
---------------------------------------------------------------------------------------------------------- 160°C/W
Operating Junction Temperature ------------------------------------------------------------------------------- 150°C
Storage Temperature Range ------------------------------------------------------------------------------------
−
65°C to +150°C
DS9262/A-11 March 2007
www.richtek.com
5
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