Richtek RT9261-27GX, RT9261-27PX, RT9261-28PB, RT9261-30GB, RT9261-30PB Schematic [ru]

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RT9261/A

VFM Step-Up DC/DC Converter

 

General Description

Features

The RT9261 Series are VFM Step-upDC/DC ICs with ultra

z Minimal Number of External Components ( Only

low supply current by CMOS process and suitable for

an Inductor, a Diode, and a Capacitor)

use with battery-powered instruments.

z Ultra Low Input Current ( 5μA at Switch Off)

The RT9261 IC consists of an oscillator, a VFM control

z ±2% High Output Voltage Accuracy

z Low Ripple and Low Noise

circuit, a driver transistor (LX switch), a reference voltage

z Low Start-up Voltage, 0.85V at 1mA

unit, an error amplifier, resistors for voltage detection, and

z 75% Efficiency with Low Cost Inductor

a LX switch protection circuit. A low ripple and high

z +50 ppm/ °C Low Temperature-Drift

efficiency step-up DC/DC converter can be constructed of

z SOT-89 and SOT-23-5 Small Packages

this RT9261 IC with only three external components.

z RoHS Compliant and 100% Lead (Pb)-Free

The RT9261A IC provides with a drive pin (EXT) for an

Applications

external transistor, so that a power transistor can be

externally applied. Therefore, the RT9261A IC is

z Power source for battery-powered equipment

recommended for applications where large currents are

z Power source for cameras, camcorders, VCRs, PDAs,

required. EN pin enables circuit to set the standby supply

pagers, electronic data banks, and hand-held

current at a maximum of 0.5μA.

communication equipment

 

Ordering Information

z Power source for applications, which require higher

voltage than that of batteries used in the appliances

RT9261/A-

 

Package Type

Pin Configurations

 

 

B : SOT-23-5

 

 

X : SOT-89

 

 

 

(TOP VIEW)

 

 

Lead Plating System

 

 

 

 

 

 

 

 

 

 

 

P : Pb Free

 

 

 

 

 

 

G : Green (Halogen Free and Pb Free)

 

 

 

 

 

 

Output Voltage

 

 

 

 

 

 

15

: 1.5V

1

2

3

1

2

3

16

: 1.6V

 

 

 

 

 

 

 

:

GND VOUT

LX

GND VOUT EXT

49

: 4.9V

50

: 5.0V

 

(TAB)

 

 

(TAB)

 

 

RT9261

 

 

RT9261A

 

Use external switch

 

 

 

 

 

 

 

SOT-89

 

 

Use internal switch

 

 

 

 

 

Note :

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Richtek products are :

LX

GND

 

EXT

GND

` RoHS compliant and compatible with the current require-

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ments of IPC/JEDEC J-STD-020.

5

 

 

 

4

 

 

5

 

 

4

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

` Suitable for use in SnPb or Pb-free soldering processes.

 

 

2

3

 

 

2

3

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Marking Information

EN VOUT NC

 

EN VOUT NC

 

 

RT9261

 

 

RT9261A

For marking information, contact our sales representative

 

 

 

 

 

 

 

 

SOT-23-5

 

 

 

 

directly or through a Richtek distributor located in your

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

area.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

DS9261/A-16 April 2011

 

 

 

 

 

 

 

 

 

 

 

www.richtek.com

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

Richtek RT9261-27GX, RT9261-27PX, RT9261-28PB, RT9261-30GB, RT9261-30PB Schematic

RT9261/A

Typical Application Circuit

 

 

D1

 

 

 

1N5819

 

L1

 

RT9261xX

 

100µH

LX

VOUT

VOUT

 

GND

+

VIN

 

COUT

 

 

22µF

 

 

 

Figure 1

 

 

D1

 

 

 

1N5819

 

L1

RT9261xB

 

100µH

LX

VOUT

VOUT

 

 

+

VIN

NC

 

COUT

 

22µF

 

 

 

EN

GND

 

 

 

 

 

L1

 

 

D1

 

 

 

 

 

27µH

 

 

1N5819

 

 

Cb

 

 

 

RT9261AxX

 

0.01µF

 

VIN

 

EXT

VOUT

VOUT

ZTX

 

 

GND

+

 

 

COUT

650 Tr

Rb

 

 

22µF

 

300

 

 

 

Figure 2

L1

 

 

D1

 

 

 

 

 

 

 

27µH

 

 

1N5819

 

 

 

 

 

 

 

VIN

 

NC

RT9261AxB

 

 

 

Cb

VOUT

+

VOUT

 

0.01µF

EXT

 

COUT

ZTX

 

 

 

22µF

 

 

EN GND

 

 

 

 

 

650

Tr

Rb

 

 

 

 

 

 

 

300

 

 

 

Figure 3

Figure 4

 

 

 

D1

 

 

 

 

1N5819

 

 

L1

RT9261xB

VOUT

 

27µH

LX

VOUT

 

 

 

+

VIN

NC

 

 

COUT

 

 

22µF

 

 

 

 

Chip

EN

 

 

GND

 

 

Enable

 

 

 

Figure 5

www.richtek.com

DS9261/A-16 April 2011

2

 

 

 

 

 

 

 

RT9261/A

Functional Pin Description

 

 

 

 

 

Pin No.

 

 

Pin Name

Pin Function

RT9261-□□□X

RT9261A-□□□X

RT9261-□□□B

RT9261A-□□□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

Chip Enable (Active High).

 

 

 

 

 

 

 

--

--

 

3

3

NC

No Internal Connected.

 

 

 

 

 

 

 

Function Block Diagram

LX

 

VLX Limiter

 

 

 

 

VREF

 

LXSW

Buffer

VOUT

 

 

 

 

 

GND

 

 

 

 

 

VFM Control

-

 

 

+

 

 

 

EXT

 

 

Error

 

OSC 100kHz

Amplifier

 

 

 

Chip Enable

 

 

 

EN

Notes:

(1)LX Pin...... only for 9261- xX and 9261- xB

(2)EXT Pin.... only for 9261A- xX and 9261A-xB

(3)EN Pin...... only for 9261- xB and 9261A- xB

DS9261/A-16 April 2011

www.richtek.com

3

RT9261/A

Absolute Maximum Ratings

z Output Voltage ------------------------------------------------------------------------------------------------------

8V

z LX Pin Voltage (1) ------------------------------------------------------------------------------------

8V

z EXT Pin Voltage (2) -------------------------------------------------------------------------------------------------

0.3 to VOUT +0.3V

z EN Pin Voltage (3) ---------------------------------------------------------------------------------------------------

0.3 to VOUT +0.3V

z LX Pin Output Current (1) ------------------------------------------------------------------------------------------

250mA

z EXT Pin Current (2) --------------------------------------------------------------------------------------------------

±50mA

z Power Dissipation, PD @ TA = 25°C

 

SOT-89 ----------------------------------------------------------------------------------------------------------------

0.5W

SOT-23-5--------------------------------------------------------------------------------------------------------------

0.25W

z Package Thermal Resistance

 

SOT-89, θJC ----------------------------------------------------------------------------------------------------------

100°C/W

SOT-89, θJA ----------------------------------------------------------------------------------------------------------

300°C/W

SOT-23-5, θJA --------------------------------------------------------------------------------------------------------

250°C/W

z Operating Temperature Range -----------------------------------------------------------------------------------

20 to +85°C

z Storage Temperature Range --------------------------------------------------------------------------------------

165°C

z Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------

260°C

Notes:

 

(1)Applicable to RT9261- xX and RT9261- xB

(2)Applicable to RT9261A- xX and RT9261A- xB

(3)Applicable to RT9261- xB and RT9261A- xB

Electrical Characteristics (Refer to Figure 1)

Parameter

Symbol

Test Conditions

 

 

Min

Typ

Max

Unit

 

 

 

 

 

 

 

 

 

 

 

Output Voltage Accuracy

VOUT

 

 

 

 

 

−2

--

2

%

Input Voltage

VIN

 

 

 

 

 

--

--

7

V

Start-up Voltage

VST

IOUT = 1mA, VIN: 0 → 2V

 

 

 

--

0.85

1

V

Hold-on Voltage

VHO

IOUT = 1mA, VIN: 2 → 0V

 

 

 

0.7

--

--

V

 

 

 

V

≤ 3.5V (1)

 

 

--

15

18

 

Input Current 1

 

VIN at no load

OUT

 

 

 

 

 

 

μA

 

3.5V < VOUT

5V

(2)

--

18

24

 

 

 

 

 

Input Current 2

 

VOUT in switch off condition

 

 

--

5

8

μA

 

 

 

 

 

 

 

 

 

 

LX Switching Current

ISWITCHING

VLX = 0.4V

VOUT ≤ 3.5V (1)

 

 

60

--

--

mA

3.5V < VOUT ≤ 5V (2)

80

--

--

LX Leakage Current

ILEAKAGE

VLX = 6V

 

 

 

 

--

--

0.5

μA

Maximum Oscillator

FMAX

 

 

 

 

 

80

120

160

kHz

Oscillator Duty Cycle

D

On ( V ” L ” ) side

VOUT = 2.5V to 5V

65

75

85

%

 

 

 

 

 

 

 

 

 

OSC

LX

VOUT = 1.5V to 2.4V

60

70

80

%

 

 

 

Efficiency

 

 

 

 

 

 

--

75

--

%

VLX Voltage Limit

 

LX switch on

 

 

 

 

0.65

0.8

1

V

Notes:

(1)Unless otherwise provided, VIN = 1.8V, VSS = 0V, IOUT = 10mA, TOPT = 25°C, and External Circuit of Typical Application (2)Unless otherwise provided, VIN = 3V, VSS = 0V, IOUT = 10mA, TOPT = 25°C, and External Circuit of Typical Application

www.richtek.com

DS9261/A-16 April 2011

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