Datasheet
Table Of Contents
- FEATURES
- APPLICATIONS
- DESCRIPTION
- ABSOLUTE MAXIMUM RATINGS
- THERMAL INFORMATION
- RECOMMENDED OPERATING CONDITIONS
- ELECTRICAL CHARACTERISTICS
- DEVICE INFORMATION
- TYPICAL CHARACTERISTICS
- APPLICATION INFORMATION
- VDDQ Switch Mode Power Supply Control
- VREF and REFIN, VDDQ Output Voltage
- Soft-Start and Powergood
- Power State Control
- MODE Pin Configuration
- Discharge Control
- D-CAP™ Mode
- D-CAP2™ Mode Operation
- Light-Load Operation
- VTT and VTTREF
- VDDQ Overvoltage and Undervoltage Protection
- VDDQ Out-of-Bound Operation
- VDDQ Overcurrent Protection
- VTT Overcurrent Protection
- V5IN Undervoltage Lockout Protection
- Thermal Shutdown
- External Components Selection
- Layout Considerations
´
³
´
OUT
SW X
V ESR
20mV
f L
£
p´ ´
SW
OUT
f
1
2 ESR C 3
( )
( )
( )
æ ö
æ ö
-
ç ÷
´ - ´ ´
ç ÷
ç ÷
ç ÷
´
´
è ø
è ø
=
IN OUT
OUT
OCL DS(on)
X
SW IN
TRIP
TRIP
V V
V
8 I R
2 L
f V
R
I
( )
( )
( )
(
)
( )
- ´
´
= + ´
´ ´
IN OUT OUT
max
TRIP TRIP
IND peak
SW IN
DS on max
V V V
R I
1
I
8 R L f V
( )
( )
(
)
( ) ( )
( )
(
)
( )
- ´ - ´
= ´ = ´
´ ´
IN OUT OUT IN OUT OUT
max max
X
SW IN O SW IN
IND ripple max max max
V V V V V V
1 3
L
I f V I f V
( )
=
æ ö
ç ÷
ç ÷
ç ÷
-
´
æ ö
ç ÷
ç ÷
-
ç ÷
ç ÷
ç ÷
è ø
è ø
IND ripple
OUT
R1
R2
1.8
1
I ESR
V
2
TPS51916
SLUSAE1D –DECEMBER 2010–REVISED JUNE 2012
www.ti.com
External Components Selection
The external components selection is simple in D-CAP™ mode.
1. DETERMINE THE VALUE OF R1 AND R2
The output voltage is determined by the value of the voltage-divider resistor, R1 and R2 as shown in Figure 35.
R1 is connected between VREF and REFIN pins, and R2 is connected between the REFIN pin and GND. Setting
R1 as 10-kΩ is a good starting point. Determine R2 using Equation 7.
(7)
2. CHOOSE THE INDUCTOR
The inductance value should be determined to yield a ripple current of approximately ¼ to ½ of maximum output
current. Larger ripple current increases output ripple voltage and improves the signal-to-noise ratio and helps
stable operation.
(8)
The inductor needs a low direct current resistance (DCR) to achieve good efficiency, as well as enough room
above peak inductor current before saturation. The peak inductor current can be estimated in Equation 9.
(9)
3. CHOOSE THE OCL SETTING RESISTANCE, R
TRIP
Combining Equation 5 and Equation 6, R
TRIP
can be obtained using Equation 10.
(10)
4. CHOOSE THE OUTPUT CAPACITORS
D-CAP™ Mode
Organic semiconductor capacitor(s) or specialty polymer capacitor(s) are recommended. Determine ESR to meet
small signal stability and recommended ripple voltage. A quick reference is shown in Equation 11 and
Equation 12.
(11)
(12)
D-CAP2™ Mode
Determine output capacitance to meet small signal stability as shown in Equation 13.
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