S-8540 Datasheet, PDF (14/36 Pages) Seiko Instruments Inc – STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER

STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
S-8540/8541 Series
Rev.3.2_00
„ Selection of Series Products and Associated External Components
1. Selecting a product
The S-8540/8541 series is classified into eight types according to the way of control (PWM and
PWM/PFM switching), the oscillation frequencies, and output voltage settings (fixed and feed back).
Please select the type that suits your needs best by taking the advantage described below into account.
1. 1 Control method:
Two different control methods are available: PWM control (S-8540 series) and PWM/PFM switching
control (S-8541 series).
1. 2 Oscillation frequencies:
The oscillation frequencies are selectable in 600 kHz (A and B types) or 300 kHz (C and D types).
Because of their high oscillation frequency, the products in the A and B types allow the use of small
size inductors since the peak current decreases when the same load current flows. In addition, they
can also be used with small output capacitors. These outstanding features make the A and B types
ideal for downsized devices.
On the other hand, the C and D types, having lower oscillation frequency, are characterized by small
self-consumption current and excellent efficiency under light load.
1. 3 Output voltage setting:
Two different types are available: fixed output (A and C types) and feed back type (B and D types).
Table 8 provides a rough guide for selecting a product depending on the requirements of the
application. Choose the product that has the best score ({).
Table 8
S-8540
S-8541
ABCDABCD
The set output voltage is fixed (1.5 to 6.0 V)
œ
œ
œ
œ
Set an output voltage freely (1.5 to 6.0 V)
The efficiency at light load (less than 10 mA) is
important.
The efficiency at 100 mA or more is important.
œ
œ
œ
œ
{{{{
{{
{{
Low-ripple voltage is important.
{{
{{
Use of small external parts is Important.
~~
Remark
œ : Indispensable condition
{ : Superiority of requirement
~ : Particularly superiority of requirement
~~
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Seiko Instruments Inc.