Preliminary
RT9261/A
VFM Step-up DC/DC Converter
General Description
The RT9261 Series are VFM Step-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 amplifier, resistors for
voltage detection, and 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 applications where large currents
are required. CE pin enables circuit to set the
standby supply current at a maximum of 0.5µA.
Features
Minimal Number of External Components ( Only
an inductor, a diode, and a capacitor)
Ultra Low Input Current ( 5µA at Switch Off)
µ
±
2% High Output Voltage Accuracy
Low Ripple and Low Noise
Low Start-up Voltage, 0.85V at 1mA
75% Efficiency with Low Cost Inductor
+50 ppm/°C Low Temperature-Drift
°
SOT-89 and SOT-25 Small Packages
Applications
Power source for battery-powered equipment
Power source for cameras, camcorders, VCRs,
PDAs, pagers, electronic data banks, and hand-
held communication equipment
Power source for applications, which require
higher voltage than that of batteries used in the
appliances
Ordering Information
RT9261A-
Package type
B : SOT-25
X : SOT-89
Operating temperature range
C: Commercial standard
Output voltage
15 : 1.5V
16 : 1.6V
:
49 : 4.9V
50 : 5.0V
A : Use external switch
Use internal switch
Pin Configurations
Part Number
RT9261-
CX
Pin Configurations
TOP VIEW
1. GND
2. VOUT (TAB)
3. LX
TOP VIEW
1. GND
2. VOUT (TAB)
3. EXT
TOP VIEW
5
4
(Plastic SOT-89)
1
2
3
RT9261A-
CX
1
2
3
(Plastic SOT-89)
RT9261-
CB
(Plastic SOT-25)
1
2
3
1.
2.
3.
4.
5.
CE
VOUT
NC
GND
LX
RT9261A-
CB
TOP VIEW
5
4
(Plastic SOT-25)
1
2
3
1.
2.
3.
4.
5.
CE
VOUT
NC
GND
EXT
DS9261/A-03 January 2002
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1
RT9261/A
Absolute Maximum Ratings
Output Voltage
LX Pin Voltage
CE Pin Voltage
(1)
(2)
Preliminary
8V
8V
-0.3 to V
OUT
+0.3V
(1)
EXT Pin Voltage
(3)
-0.3 to V
OUT
+0.3V
250mA
±50mA
0.5W
0.25W
100°C/W
300°C/W
250°C/W
-20 to +85°C
165°C
260°C
CB
CB
CB
LX Pin Output Current
EXT Pin Current
SOT-89
SOT-25
(2)
Power Dissipation, P
D
@ T
A
= 25°C
Package Thermal Resistance
SOT-89,
θ
JC
SOT-89,
θ
JA
SOT-25,
θ
JA
Operating Temperature Range
Storage Temperature Range
Lead Temperature (Soldering, 10 sec.)
Notes:
(1) Applicable to RT9261-
(2) Applicable to RT9261A-
(3) Applicable to RT9261-
CX and RT9261-
CX and RT9261A-
CB and RT9261A-
Electrical Characteristics
(Refer to Fig. 1)
Parameter
Output Voltage Accuracy
Input Voltage
Start-up Voltage
Hold-on Voltage
Input Current 1
Input Current 2
LX Switching Current
LX Leakage Current
Maximum Oscillator
Oscillator Duty Cycle
Efficiency
V
LX
Voltage Limit
Notes:
(1) V
IN
= 1.8V, VSS = 0V, I
OUT
= 10mA, T
OPT
= 25°C, and External Circuit of Typical Application
(2) V
IN
= 3V, VSS = 0V, I
OUT
= 10mA, T
OPT
= 25°C, and External Circuit of Typical Application
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DS9261/A-03 January 2002
(1)
(2)
Symbol
∆V
OUT
V
IN
V
ST
V
HO
Test Conditions
Min
-2
--
Typ
--
--
0.85
--
15
18
5
--
--
--
120
75
75
0.8
Max Units
+2
7
1.0
--
18
24
8
--
--
0.5
160
85
--
1.0
%
V
V
V
µA
µA
mA
µA
KHz
%
%
V
I
OUT
= 1mA, V
IN
: 0
→
2V
I
OUT
= 1mA, V
IN
: 2
→
0V
To be measured at V
IN
at
no load
To be measured at V
OUT
in switch off condition
--
0.7
--
--
--
60
80
--
80
65
--
0.65
V
OUT
≤
3.5V
3.5V
<
V
OUT
≤
5V
V
OUT
≤
3.5V
(1)
(2)
I
SWITCHING
3.5V
<
V
OUT
≤
5V
V
LX
= 0.4V
V
LX
= 6V
On ( V
LX
” L ” ) side
L
X
switch on
I
LEAKAGE
F
MAX
D
OSC
2
Preliminary
Electrical Characteristics
(Refer to Fig. 2)
Parameter
Output Voltage Accuracy
Input Voltage
Start-up Voltage
Input Current 1
Input Current 2
EXT “H” Output
Current
EXT “L” Output
Current
V
OUT
≤
3.5V
V
OUT
≤
3.5V
V
OUT
≤
3.5V
V
OUT
≤
3.5V
(1)
(2)
RT9261/A
Min
-2
--
Typ
--
--
0.85
30
60
6
--
--
--
--
120
75
Max Units
+2
7
1.0
50
90
10
--
--
--
--
160
85
%
V
V
µA
µA
mA
mA
KHz
%
Symbol
∆V
OUT
V
IN
V
ST
Test Conditions
I
OUT
= 1mA, V
IN
: 0
→
2V
To be measured at V
IN
at no
load
To be measured at V
OUT
in
switch off condition
V
EXT
= V
OUT
– 0.4V
V
EXT
= 0.4V
--
--
--
--
-1.5
-2
1.5
2
80
65
3.5V
<
V
OUT
≤
5V
(1)
3.5V
<
V
OUT
≤
5V
(1)
(2)
3.5V
<
V
OUT
≤
5V
(1)
(2)
3.5V
<
V
OUT
≤
5V
(2)
Maximum Oscillator Frequency
Oscillator Duty Cycle
Notes:
F
MAX
D
OSC
V
EXT
” H ” side
(1) Unless otherwise provided, V
IN
= 1.8V, VSS = 0V, I
OUT
= 10mA, T
OPT
= 25°C, and use External Circuit of
Typical Application
(2) Unless otherwise provided, V
IN
= 3V, VSS = 0V, I
OUT
= 10mA, T
OPT
= 25°C, and External Circuit of Typical
Application
DS9261/A-03 January 2002
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3
RT9261/A
Parameter
Output Voltage Accuracy
Input Voltage
Start-up Voltage
Hold-on Voltage
Efficiency
Input Current 1
Input Current 2
LX Switching
Current
V
OUT
≤
3.5V
V
OUT
≤
3.5V
V
OUT
≤
3.5V
V
OUT
≤
3.5V
(1)
(2)
Preliminary
Electrical Characteristics
(Refer to Fig. 3)
Symbol
∆V
OUT
V
IN
V
ST
V
HO
3.5V
<
V
OUT
≤
5V
(1)
(2)
Test Conditions
Min
-2
--
--
0.7
--
--
--
--
--
--
60
80
--
0.4× V
OUT
--
--
-0.5
80
65
0.65
Typ
--
--
0.85
--
75
85
15
18
5
6
--
--
--
--
--
--
--
120
75
0.8
Max
+2
7
1.0
--
--
--
18
24
8
10
--
--
0.5
--
0.2
0.5
--
160
85
1.0
Units
%
V
V
V
%
µA
µA
mA
µA
V
V
µA
µA
KHz
%
V
I
OUT
= 1mA, V
IN
: 0
→
2V
I
OUT
= 1mA, V
IN
: 2
→
0V
3.5V
<
V
OUT
≤
5V
(1)
To be measured at V
IN
at
no load
To be measured at V
OUT
in switch off condition
I
SWITCHING
I
LEAKAGE
V
LX
= 0.4V
V
LX
= 6V
V
IN
= V
OUT
×
0.9
V
IN
= V
OUT
×
0.9
CE = V
OUT
CE = 0V
F
MAX
D
OSC
On (V
LX
” L” ) side
LX switch on
3.5V
<
V
OUT
≤
5V
(1)
(2)
3.5V
<
V
OUT
≤
5V
(2)
LX Leakage Current
CE “H” Level
CE “ L” Level
CE “ H” Input Current
CE “ L“ Input Current
Maximum Oscillator Frequency
Oscillator Duty Cycle
V
LX
Voltage Limit
Notes:
(1) Unless otherwise provided, V
IN
= 1.8V, VSS = 0V, I
OUT
= 10mA, T
OPT
= 25°C, and use External Circuit of
Typical Application
(2) Unless otherwise provided, V
IN
= 3V, VSS = 0V, I
OUT
= 10mA, T
OPT
= 25°C, and External Circuit of Typical
Application
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DS9261/A-03 January 2002
4
Preliminary
Electrical Characteristics
(Refer to Fig. 4)
Parameter
Output Voltage Accuracy
Input Voltage
Start-up Voltage
Efficiency
Input Current 1
Input Current 2
EXT “H” Output
Current
EXT “L” Output
Current
CE “H” Level
CE “ L” Level
CE “ H” Input Current
CE “ L“ Input Current
Maximum Oscillator Frequency
Oscillator Duty Cycle
V
LX
Voltage Limit
Notes:
F
MAX
D
OSC
On (V
LX
” L” ) side
LX switch on
V
OUT
≤
3.5V
V
OUT
≤
3.5V
V
OUT
≤
3.5V
V
OUT
≤
3.5V
V
OUT
≤
3.5V
(1)
(2)
RT9261/A
Min
-2
--
--
--
--
--
--
--
-1.5
-2
1.5
2
0.4× V
OUT
--
--
-0.5
80
65
0.65
Typ
--
--
0.85
75
85
30
60
6
--
--
--
--
--
--
--
--
120
75
0.8
Max
+2
7
1.0
--
--
50
90
10
--
--
--
--
--
0.2
0.5
--
160
85
1.0
Units
%
V
V
%
µA
µA
mA
mA
V
V
µA
µA
KHz
%
V
Symbol
∆V
OUT
V
IN
V
ST
Test Conditions
I
OUT
= 1mA, V
IN
: 0
→
2V
3.5V
<
V
OUT
≤
5V
(1)
3.5V
<
V
OUT
≤
5V
(1)
(2)
To be measured at V
IN
at
no load
To be measured at V
OUT
in
switch off condition
V
EXT
= V
OUT
– 0.4V
V
EXT
= 0.4V
V
IN
= V
OUT
×
0.9
V
IN
= V
OUT
×
0.9
CE = V
OUT
CE = 0V
3.5V
<
V
OUT
≤
5V
(1)
(2)
3.5V
<
V
OUT
≤
5V
(1)
(2)
3.5V
<
V
OUT
≤
5V
(2)
(1) Unless otherwise provided, V
IN
= 1.8V, VSS = 0V, I
OUT
= 10mA, T
OPT
= 25°C, and use External Circuit of
Typical Application
(2) Unless otherwise provided, V
IN
= 3V, VSS = 0V, I
OUT
= 10mA, T
OPT
= 25°C, and External Circuit of Typical
Application
DS9261/A-03 January 2002
www.richtek-ic.com.tw
5
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