ST5R00
SERIES
MICROPOWER VFM STEP-UP DC/DC CONVERTER
■
■
■
■
■
■
■
■
■
■
VERY LOW SUPPLY CURRENT
REGULATED OUTPUT VOLTAGE
WIDE RANGE OF OUTPUT VOLTAGE
AVAILABLE (2.5V, 2.8V, 3.0V, 3.3V, 5.0V)
OUTPUT VOLTAGE ACCURACY ±5%
OUTPUT CURRENT UP TO 100mA
LOW RIPPLE AND LOW NOISE
VERY LOW START-UP VOLTAGE
HIGH EFFICIENCY (VOUT = 5V TYP. 87%)
FEW EXTERNAL COMPONENTS
VERY SMALL PACKAGE: SOT23-5L
DESCRIPTION
The ST5R00 is an high efficiency VFM Step-up
DC/DC converter for small, low input voltage or
battery powered systems with ultra low quiescent
supply current. The ST5Rxx accept a positive
input voltage from start-up voltage to VOUT and
convert it to a higher output voltage in the 2.5 to
5V range.
The ST5R00 combine ultra low quiescent supply
current and high efficiency to give maximum
battery life. The high switching frequency and the
internally limited peak inductor current, permits
SOT23-5L
the use of small, low cost inductors. Only three
external components are needed: an inductor a
diode and an output capacitor.
The ST5R00 is suitable to be used in a battery
powered equipment where low noise, low ripple
and ultra low supply current are required. The
ST5R00 is available in very small packages:
SOT23-5L.
Typical applications are pagers, cameras & video
camera, cellular telephones, wireless telephones,
palmtop computer, battery backup supplies,
battery powered equipment.
Figure 1: Schematic Diagram
June 2005
Rev. 6
1/15
ST5R00 SERIES
Table 1: Absolute Maximum Ratings
Symbol
VOUT
Parameter
Value
Unit
Output Voltage
5.5
V
VIN
Input Voltage
5.5
V
VLX
LX Pin Voltage
5.5
V
ILX
LX Pin Output Current
Internally limited
PTOT
Power Dissipation at 25°C
TSTG
Storage Temperature Range
-55 to 125
°C
TOP
Operating Junction Temperature Range
-25 to 85
°C
170 (*)
mW
(*) Reduced by 1.7 mW for increasing in TA of 1°C over 25°C
Absolute Maximum Ratings are those values beyond which damage to the device may occur. Functional operation under these condition is
not implied.
Table 2: Thermal Data
Symbol
Rthj-case
Parameter
Thermal Resistance Junction-case
SOT23-5L
Unit
63
°C/W
Figure 2: Connection Diagram (top view)
Table 3: Order Codes
2/15
SOT23-5L
OUTPUT VOLTAGES
ST5R25MTR
ST5R28MTR
ST5R30MTR
ST5R33MTR
ST5R50MTR
2.5 V
2.8 V
3.0 V
3.3 V
5.0 V
ST5R00 SERIES
OPERATION
The ST5Rxx architecture is built around a VFM CONTROL logic core: switching frequency is set through
a built in oscillator: TON time is fixed (Typ. 5ms) while TOFF time is determined by the error amplifier
output, a logic signal coming from the comparison made by the Error Amplifier Stage between the signal
coming from the output voltage divider network and the internal Band-Gap voltage reference (Vref). TOFF
reaches a minimum (Typ. 1.7ms) when heavy load conditions are met (Clock frequency 150KHz). An over
current conditions, through the internal power switch, causes a voltage drop VLX=R DSONxISW and the VLX
limiter block forces the internal switch to be off, so narrowing TON time and limiting internal power
dissipation. In this case the switching frequency may be higher than the 150KHz set by the internal clock
generator.
VFM control ensures very low quiescent current and high conversion efficiency even with very light loads.
Since the Output Voltage pin is also used as the device Supply Voltage, the versions with higher output
voltage present an higher internal supply voltage that results in lower power switch RDSON, slightly greater
output power and higher efficiency. Moreover, bootstrapping allows the input voltage to sag to 0.6V (at
IOUT=1mA) once the system is started.
If the input voltage exceeds the output voltage, the output will follow the input, however, the input or output
voltage must not be forced above 5.5V.
Figure 3: Typical Application Circuit
(*) See application info.
Figure 4: Typical Application Efficiency
3/15
ST5R00 SERIES
Figure 5: Typical Demoboard
Note: drawing not in scale.
Table 4: Electrical Characteristics For ST5R25
(VIN = 1.5V, IOUT = 10mA, TA = 25°C, unless otherwise specified. For external components value, unless
otherwise notes, refer to the typical operating circuit.)
Symbol
VOUT
Parameter
Test Conditions
Output Voltage
Min.
2.375
Typ.
Max.
Unit
2.5
2.625
V
0.8
1.2
V
VSTART-UP Start-up Voltage (VIN-VF) (1)
IOUT = 1mA, VIN = rising from 0 to 2V
VHOLD
Hold-on Voltage
IOUT = 1mA, VIN = falling from 2 to 0V
ISUPPLY
Supply Current
To be measured at VIN, no load
16
µA
ILX = 150mA
850
mΩ
RLX(DSON) Internal Switch RDSON
ILX(leak) Internal Leakage Current
fOSC
Dty
ν
0.6
V
VLX = 4V, forced VOUT = 3V
0.5
Maximum oscillator Frequency
150
µA
KHz
Oscillator Duty Cycle
to be measure on LX pin
77
%
Efficiency
IOUT = 50mA
82
%
(1): The minimum input voltage for the IC start-up is strictly a function of the VF catch diode.
Table 5: Electrical Characteristics For ST5R28
(VIN = 1.7V, IOUT = 10mA, TA = 25°C, unless otherwise specified. For external components value, unless
otherwise notes, refer to the typical operating circuit.)
Symbol
VOUT
Parameter
Test Conditions
Output Voltage
VSTART-UP Start-up Voltage (VIN-VF) (1)
Min.
2.66
IOUT = 1mA, VIN = rising from 0 to 2V
Typ.
Max.
2.8
2.94
V
0.8
1.2
V
VHOLD
Hold-on Voltage
IOUT = 1mA, VIN = falling from 2 to 0V
ISUPPLY
Supply Current
To be measured at VIN, no load
16
µA
ILX = 150mA
850
mΩ
RLX(DSON) Internal Switch RDSON
ILX(leak) Internal Leakage Current
fOSC
Dty
ν
V
VLX = 4V, forced VOUT = 3.3V
Maximum oscillator Frequency
0.5
150
µA
KHz
Oscillator Duty Cycle
to be measure on LX pin
77
%
Efficiency
IOUT = 50mA
82
%
(1): The minimum input voltage for the IC start-up is strictly a function of the VF catch diode.
4/15
0.6
Unit
ST5R00 SERIES
Table 6: Electrical Characteristics For ST5R30
(VIN = 1.8V, IOUT = 10mA, TA = 25°C, unless otherwise specified. For external components value, unless
otherwise notes, refer to the typical operating circuit.)
Symbol
VOUT
Parameter
Test Conditions
Output Voltage
VSTART-UP Start-up Voltage (VIN-VF) (1)
Min.
Typ.
Max.
Unit
2.85
3
3.15
V
0.8
1.2
V
IOUT = 1mA, VIN = rising from 0 to 2V
VHOLD
Hold-on Voltage
IOUT = 1mA, VIN = falling from 2 to 0V
ISUPPLY
Supply Current
To be measured at VIN, no load
17
µA
ILX = 150mA
850
mΩ
RLX(DSON) Internal Switch RDSON
ILX(leak) Internal Leakage Current
fOSC
Dty
ν
0.6
V
VLX = 4V, forced VOUT = 3.5V
0.5
Maximum oscillator Frequency
150
µA
KHz
Oscillator Duty Cycle
to be measure on LX pin
77
%
Efficiency
IOUT = 50mA
82
%
(1): The minimum input voltage for the IC start-up is strictly a function of the VF catch diode.
Table 7: Electrical Characteristics For ST5R33
(VIN = 2V, IOUT = 10mA, TA = 25°C, unless otherwise specified. For external components value, unless
otherwise notes, refer to the typical operating circuit.)
Symbol
VOUT
Parameter
Test Conditions
Output Voltage
VSTART-UP Start-up Voltage (VIN-VF) (1)
Min.
3.135
IOUT = 1mA, VIN = rising from 0 to 2V
Typ.
Max.
3.3
3.465
V
0.8
1.2
V
VHOLD
Hold-on Voltage
IOUT = 1mA, VIN = falling from 2 to 0V
ISUPPLY
Supply Current
To be measured at VIN, no load
17
ILX = 150mA
850
RLX(DSON) Internal Switch RDSON
ILX(leak)
fOSC
Dty
ν
Internal Leakage Current
0.6
V
VLX = 4V, forced VOUT = 3.8V
µA
mΩ
0.5
Maximum oscillator Frequency
Unit
µA
150
KHz
Oscillator Duty Cycle
to be measure on LX pin
77
%
Efficiency
IOUT = 50mA
83
%
(1): The minimum input voltage for the IC start-up is strictly a function of the VF catch diode.
Table 8: Electrical Characteristics For ST5R50
(VIN = 3V, IOUT = 10mA, TA = 25°C, unless otherwise specified. For external components value, unless
otherwise notes, refer to the typical operating circuit.)
Symbol
VOUT
Parameter
Test Conditions
Output Voltage
Min.
Typ.
Max.
Unit
4.75
5.0
5.25
V
0.8
1.2
V
VSTART-UP Start-up Voltage (VIN-VF) (1)
IOUT = 1mA, VIN = rising from 0 to 2V
VHOLD
Hold-on Voltage
IOUT = 1mA, VIN = falling from 2 to 0V
ISUPPLY
Supply Current
To be measured at VIN, no load
18
µA
ILX = 150mA
700
mΩ
RLX(DSON) Internal Switch RDSON
ILX(leak) Internal Leakage Current
fOSC
Dty
ν
0.6
V
VLX = 4V, forced VOUT = 3.8V
Maximum oscillator Frequency
0.5
µA
160
KHz
Oscillator Duty Cycle
to be measure on LX pin
77
%
Efficiency
IOUT = 50mA
87
%
(1): The minimum input voltage for the IC start-up is strictly a function of the VF catch diode.
5/15
ST5R00 SERIES
TYPICAL PERFORMANCE CHARACTERISTICS (the following plots are referred to the typical
application circuit and, unless otherwise noted, at TA = 25°C)
Figure 6: Output Voltage vs Output Current
Figure 9: Output Voltage vs Temperature
Figure 7: Output Voltage vs Output Current
Figure 10: Efficiency vs Temperature
Figure 8: Output Voltage vs Temperature
Figure 11: Efficiency vs Temperature
6/15
ST5R00 SERIES
Figure 12: Efficiency vs Output Current
Figure 15: Maximum Oscillator Frequency vs
Temperature
Figure 13: Efficiency vs Output Current
Figure 16: Oscillator Duty Cycle (@ MAX Freq.)
vs Temperature
Figure 14: Maximum Oscillator Frequency vs
Temperature
Figure 17: Oscillator Duty Cycle (@ MAX Freq.)
vs Temperature
7/15
ST5R00 SERIES
Figure 18: LX Switching Current Limit vs
Temperature
Figure 21: Start-up Voltage (VIN - VF) vs
Temperature
Figure 19: LX Switching Current Limit vs
Temperature
Figure 22: Start-up Voltage (VIN - VF) vs
Output Current
Figure 20: Start-up Voltage (VIN - VF) vs
Temperature
Figure 23: Start-up Voltage (VIN - VF) vs
Output Current
8/15
ST5R00 SERIES
Figure 24: Minimum Input Voltage vs Output
Current
Figure 27: Internal Switch RDSON vs
Temperature
Figure 25: Minimum Input Voltage vs Output
Current
Figure 28: Hold-on Voltage vs Temperature
Figure 26: Internal Switch RDSON vs
Temperature
Figure 29: Hold-on Voltage vs Temperature
9/15
ST5R00 SERIES
Figure 30: No Load Input Current vs
Temperature
Figure 31: No Load Input Current vs
Temperature
APPLICATION INFORMATION
PC LAYOUT AND GROUNDING HINTS
The ST5R00 high frequency operation makes PC layout important for minimizing ground bounce and
noise. Place external components as close as possible to the device pins. Take care to the Supply
Voltage Source connections that have to be very close to the Input of the application. Set the Output Load
as close as possible to the output capacitor. If possible, use a Star ground connection with the centre point
on the Device Ground pin. To maximize output power and efficiency and minimize output ripple voltage,
use a ground plane and solder the ICs ground pin directly to the ground plane.
Remember that the LX Switching Current flows through the Ground pin, so, in order to minimize the series
resistance that may cause power dissipation and decrease of the Efficiency conversion, the Ground
pattern has to be as large as possible.
INDUCTOR SELECTION
An inductor value of 47µH performs well in most ST5R00 applications. However, the inductance value is
not critical, and the ST5R00 will work with inductors in the 33µH to 120µH. Smaller inductance values
typically offer a smaller physical size for a given series resistance, allowing the smallest overall circuit
dimensions. However, due to higher peak inductor currents, the output voltage ripple (Ipeak x output filter
capacitors ESR) also tends to be higher. Circuits using larger inductance values exhibit higher output
current capability and larger physical dimensions for a given series resistance.
In order to obtain the best application performances the inductor must respect the following condition:
- The DC resistance has to be as little as possible, a good value is