Datasheet

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APPLICATION INFORMATION
ADJUSTABLE OUTPUT VOLTAGE
V
O
+ 1.5 V
ref
ǒ
1 )
R1
R2
Ǔ
with an internal reference voltage V
ref
typical + 0.4 V
(2)
AVIN
VIN SW
TPS62300
L1
ADJ
C1
PGND
C2
V
I
AGND
VOUT
R1
R2
EN
MODE/SYNC
A
A
FB
A
1
2
3
8
7
10
6
4
5
9
V
O
1.6V/500mA
2.7V..6V
4.7 Fm
4.7 Fm
OUTPUT FILTER DESIGN (INDUCTOR AND OUTPUT CAPACITOR)
ƒ
c
+
1
2p L C
O
Ǹ
+
1
2p 1 mH 10 mF
Ǹ
+ 50.3 kHz
(3)
TPS62300, TPS62301, TPS62302
TPS62303, TPS62304, TPS62305,
TPS62311, TPS62313, TPS62315, TPS62320, TPS62321
SLVS528E – JULY 2004 – REVISED NOVEMBER 2007
When the adjustable output voltage versions, TPS62300 or TPS62320, are used, the output voltage is set by the
external resistor divider (see Figure 32 ).
The output voltage is calculated as:
To keep the operating quiescent current to a minimum, it is recommended that R2 be set in the range of 75 k Ω to
130 k Ω . Route the FB line away from noise sources, such as the inductor or the SW line.
Figure 32. Adjustable Output Voltage Version
The TPS6230x, TPS6231x, and TPS6232x series of step-down converters have internal loop compensation.
Therefore, the external L-C filter must be selected to work with the internal compensation.
The device has been designed to operate with inductance values between a minimum of 0.7 µ H and maximum of
6.2 µ H. The internal compensation is optimized to operate with an output filter of L = 1 µ H and C
O
= 10 µ F. Such
an output filter has its corner frequency at:
Operation with a higher corner frequency (e.g., L = 1 µ H, C
O
= 4.7 µ F) is possible. However, it is recommended
the loop stability be checked in detail. Selecting a larger output capacitor value (e.g., 22 µ F) is less critical
because the corner frequency moves to lower frequencies with fewer stability problems. The possible output filter
combinations are listed in Table 1 .
Regardless of the inductance value, operation is recommended with 10- µ F output capacitor in applications with
high-load transients (e.g., ≥ 1600 mA/ µ s).
Table 1. Output Filter Combinations
INDUCTANCE (L) OUTPUT CAPACITANCE (C
O
)
1 µ H ≥ 4.7 µ F (ceramic capacitor)
2.2 µ H ≥ 2.2 µ F (ceramic capacitor)
The inductor value also has an impact on the pulse skipping operation. The transition into power-save mode
begins when the valley inductor current goes below a level set internally. Lower inductor values result in higher
ripple current which occurs at lower load currents. This results in a dip in efficiency at light load operations.
18 Submit Documentation Feedback Copyright © 2004 – 2007, Texas Instruments Incorporated
Product Folder Link(s): TPS62300, TPS62301, TPS62302 TPS62303, TPS62304, TPS62305, TPS62311, TPS62313,
TPS62315, TPS62320, TPS62321