SIP1759 データシートの表示（PDF） - Vishay Semiconductors
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SIP1759 Datasheet PDF : 8 Pages
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DESIGNS CONSIDERATIONS
Setting the Adjustable Output Voltage
The SiP1759 regulated output can be adjusted from 2.5 V to
5.5 V via resistor divider network from VOUT to GND (see
Typical Application Circuits). R1 and R2 should be kept in the
50 kΩ to 100 kΩ range for low power consumption, while
maintaining adequate noise immunity. The value R1 is
calculated using the following formula:
R1 = R2 {(VOUT/VFB) - 1}
VFB is nominally 1.235 V.
Capacitor Selection
Capacitor selection for CIN, COUT and CX will have an impact
in the voltage output ripple, output current and overall
physical size of the circuit.
TYPICAL CHARACTERISTICS
120
IOUT at 10 mA
100
IOUT at 50 mA
80
IOUT at 100 mA
60
40
20
0
1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
Input Voltage (V)
Efficiency vs. Input Voltage
4.0
3.5
(VOUT < VIN) RLOAD = 33 Ω
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
Input Voltage (V)
Start-Up Input Voltage
SiP1759
Vishay Siliconix
Ceramic capacitors are recommenced for their low ESR
(≤ 20 mΩ) which will help keep the output voltage ripple at a
minimum. The initial values for the CIN and COUT capacitors
should be 10 µF, the CX capacitor should be 0.33 µF.
Output Voltage Ripple
The SiP1759 automatically decides whether to be in step up
mode or step down mode depending on the VIN, VOUT and
current load conditions, therefore the voltage output ripple
will vary. In step-up mode the voltage output ripple is higher
than step-down mode. But unless VIN is significant larger
than VOUT (VIN ≥ VOUT + 1 V) , in heavy load the IC will slip
from buck mode to boost mode as necessary to charge the
transfer capacitor and the ripple will increase. Reducing the
CX capacitor value will cause an increase in the switching
frequency and a reduction of the output ripple.
1.00E-01
1.00E-02
1.00E-03
1.00E-04
1.00E-05
1.00E-06
1.00E-07
0.5
1.5
2.5
3.5
4.5
5.5
Input Voltage (V)
Quiescent Current vs. Input Voltage (No Load)
0.20
0.16
100 mA
0.12
0.08
50 mA
0.04
10 mA
0.00
1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
Input Voltage (V)
Output voltage Ripple vs. Input Voltage
Document Number: 72949
S09-1453-Rev. D, 03-Aug-09
www.vishay.com
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