Richtek RT9261-27GX, RT9261-27PX, RT9261-28PB, RT9261-30GB, RT9261-30PB Schematic [ru]
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VFM Step-Up DC/DC Converter
RT9261/A
General Description
The RT9261 Series are VFM Ste p-up DC/DC ICs with ultra
low supply current by CMOS process and suitable for
use with battery-powered instruments.
The RT9261 IC consists of an oscillator, a VFM control
circuit, a driver transistor (LX switch), a reference voltage
unit, an error a mplifier , resistors for voltage detection, a nd
a LX switch protection circuit. A low ripple and high
efficiency step-up DC/DC converter can be constructed of
this RT9261 IC with only three external components.
The RT9261A IC provides with a drive pin (EXT) for an
external transistor, so that a power transistor can be
externally applied. Therefore, the RT9261A IC is
recommended for a pplication s where large currents are
required. EN pin ena bles circuit to set the standby supply
current at a maximum of 0.5μA.
Ordering Information
RT9261/A-
Features
zz
Minimal Number of External Components ( Only
z
zz
an Inductor, a Diode, and a Capacitor)
zz
z Ultra Low Input Current ( 5
zz
±±
zz
z
±2% High Output V oltage Accura cy
zz
±±
zz
z Low Ripple and Low Noise
zz
zz
z Low Start-up Voltage, 0.85V at 1mA
zz
zz
z 75% Efficiency with Low Cost Inductor
zz
zz
z +50 ppm/
zz
zz
z SOT-89 and SOT-23-5 Small Pa c kages
zz
zz
z RoHS Compliant and 100% Lead (Pb)-Free
zz
°°
°C Low Temperature-Drift
°°
μμ
μA at Switch Off)
μμ
Applications
z Power source for battery-powered equipment
z Power source for ca mera s, ca mcorders, VCRs, PDAs,
pagers, electronic data ban ks, and ha nd-held
communication equipment
z Power source for a pplications, which require higher
voltage than that of batteries used in the a ppli ances
Package Type
B : SOT-23-5
X : SOT-89
Lead Plating System
P : Pb Free
G : Green (Halogen Free and Pb Free)
Output Voltage
15 : 1.5V
16 : 1.6V
:
49 : 4.9V
50 : 5.0V
Use external switch
Use internal switch
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.
Marking Information
For marking information, conta ct our sales representative
directly or through a Richtek distributor located in your
area.
Pin Configurations
(TOP VIEW)
123
GND
VOUT
RT9261
LX GND
5
EN VOUT NC
LX
(TAB)
SOT-89
4
23
SOT-23-5
123
EXT
VOUT
GND
(TAB)
RT9261A
EXT GND
5
EN VOUT NC
4
23
RT9261ART9261
DS9261/A-16 April 2011 www.richtek.com
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RT9261/A
T ypical Application Circuit
D1
1N5819
L1
100µH
V
IN
RT9261xX
VOUTLX
GND
+
C
OUT
22µF
V
OUT
V
IN
L1
27µH
ZTX
650
0.01µF
Tr
Cb
Rb
300
D1
1N5819
RT9261AxX
VOUTEXT
GND
+
C
OUT
22µF
V
OUT
Figure 1 Figure 2
D1
1N5819
L1
100µH
V
IN
NC
RT9261xB
LX
EN
GND
VOUT
+
C
OUT
22µF
V
OUT
V
IN
L1
27µH
ZTX
650
0.01µF
Tr
Cb
Rb
300
NC
1N5819
RT9261AxB
EXT
EN
GND
D1
VOUT
+
C
OUT
22µF
V
OUT
Figure 3 Figure 4
D1
1N5819
L1
27µH
V
IN
NC
Chip
Enable
RT9261xB
LX
EN
GND
VOUT
+
C
OUT
22µF
V
OUT
Figure 5
DS9261/A-16 April 2011www.richtek.com
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Functional Pin Description
RT9261/A
Pin No .
RT9261-□□□X RT9261A-□□□X RT9261-□□□B R T9261A-□□□B
1 1 4 4 GND Ground.
2 2 2 2 VOUT Output Voltage.
3 -- 5 -- LX Pin for Switching.
-- 3 -- 5 EXT Drive External Device.
-- -- 1 1 EN
-- -- 3 3 NC No Internal Connected.
Function Block Diagram
LX
LXSW
GND
EXT
VLX Limiter
Buffer
VFM Control
OSC 100kHz
+
Error
Amplifier
P in Name Pin Function
V
REF
Chip Enable (Active High).
VOUT
Notes:
(1) LX Pin...... only for 9261- xX and 9261- xB
(2) EXT Pin.... only for 9261A- xX a nd 9261A- xB
(3) EN Pin...... only for 9261- xB and 9261A- xB
Chip Enable
EN
DS9261/A-16 April 2011 www.richtek.com
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RT9261/A
Absolute Maximum Ratings
z Output V oltage ------------------------------------------------------------------------------------------------------ 8V
z LX Pin V oltage
z EXT Pin V oltage
z EN Pin Voltage
z LX Pin Output Current
z EXT Pin Current
z Power Dissipation, P
SOT-89 ---------------------------------------------------------------------------------------------------------------- 0.5W
SOT-23-5-------------------------------------------------------------------------------------------------------------- 0.25W
z Pack age Thermal Resistance
SOT-89, θJC---------------------------------------------------------------------------------------------------------- 100°C/W
SOT -89, θJA---------------------------------------------------------------------------------------------------------- 300°C/W
SOT-23-5, θJA-------------------------------------------------------------------------------------------------------- 250°C/W
z Operating T emperature Range ----------------------------------------------------------------------------------- −20 to +85°C
z Storage T emperature Range-------------------------------------------------------------------------------------- 165°C
z Lead T emperature (Soldering, 10 sec.) ------------------------------------------------------------------------ 260°C
Notes:
(1) Applicable to R T9261- xX and RT9261- xB
(2) Applicable to R T9261A- xX and RT9261A- xB
(3) Applicable to RT9261- xB and RT9261A- xB
(1)
------------------------------------------------------------------------------------8V
(2)
------------------------------------------------------------------------------------------------- −0.3 to V
(3)
--------------------------------------------------------------------------------------------------- −0.3 to V
(1)
------------------------------------------------------------------------------------------ 250mA
(2)
-------------------------------------------------------------------------------------------------- ±50mA
@ T
D
= 25°C
A
OUT
OUT
+0.3V
+0.3V
Electrical Characteristics (Refer to Figure 1)
Parameter Symbol Test Conditions Min Typ Max Unit
Output Voltage Accuracy ΔV
In put Volt age VIN -- -- 7 V
Start - u p Volt a g e VST I
Hol d-on Voltage VHO I
In put Cu rr en t 1 V
In put Cu rr en t 2 V
LX Swi tc hing Curr e nt I
LX Lea ka ge Cu rr en t I
Maximum Oscillator F
Oscillator Duty Cycle D
Efficiency -- 75 -- %
VLX Voltage Limit LX switch on 0.65 0.8 1 V
Notes:
(1)Unless otherwise provided, V
(2)Unless otherwise provided, V
−2 -- 2 %
OUT
= 1mA, VIN: 0 → 2V -- 0.85 1 V
OUT
= 1mA, VIN: 2 → 0V 0.7 -- -- V
OUT
V
≤ 3.5V
at no load
IN
in switch off condition -- 5 8 μA
OUT
SWITCHING
LEAKAGE
MAX
OSC
= 1.8V, VSS = 0V, I
IN
= 3V, VSS = 0V, I
IN
V
V
80 120 160 kHz
On ( V
= 0.4V
LX
= 6V -- -- 0.5 μA
LX
” L ” ) side
LX
= 10mA, T
OUT
= 10mA, T
OUT
OUT
3.5V < V
V
≤ 3. 5V
OUT
3.5V < V
V
= 2.5V to 5V 65 75 85 %
OUT
= 1.5V to 2.4V 60 70 80 %
V
OUT
= 25°C, and External Circuit of Typical Application
OPT
= 25°C, and External Circuit of Typical Application
OPT
(1)
-- 15 18
(2)
OUT
OUT
≤ 5V
(1)
≤ 5V
-- 18 24
60 -- --
(2)
80 -- --
μA
mA
DS9261/A-16 April 2011www.richtek.com
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