S-8540A15FN-IAAT2Z Datasheet, PDF (19/36 Pages) Seiko Instruments Inc – SWITCHABLE SWITCHING REGULATOR CONTROLLER

STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.4.0_01
S-8540/8541 Series
 Precautions
 Install the external capacitors, diode, coil, and other peripheral components as close to the IC as possible,
and make a one-point grounding.
When the input voltage is 9 to 10 V, VOUT may vary largely according to the grounding method.
When it is difficult to make one-point grounding, use two grounds: one for VIN, CIN, and SD GND, and the
other for VOUT, VCVREF, and IC GND.
 Characteristics ripple voltage and spike noise occur in IC containing switching regulators. Moreover rush
current flows at the time of a power supply injection. Because these largely depend on the inductor, the
capacitor and impedance of power supply used, fully check them using an actually mounted model.
 If the input voltage is high and output current is low, pulses with a low duty ratio may appear, and then the
0% duty ratio continues for several clocks. In this case the operation changes to the pseudo pulse
frequency modulation (PFM) mode, but the ripple voltage hardly increases.
 If the input power supply voltage is lower than 1.0 V, the IC operation is unstable and the external switch
may be turned on.
If input power supply voltage is 10.0 V or higher, the circuit operation is unstable and the IC may be
damaged.
The input voltage must be in the standard range (2.5 to 10.0 V).
 The current limit circuit of the IC limits current by detecting a voltage difference of external resistor RSENSE.
In choosing the components, make sure that overcurrent will not surpass the allowable dissipation of the
switching transistor and the inductor.
 Make sure that dissipation of the switching transistor will not surpass the allowable power dissipation of the
package (especially at high temperature).
 Do not apply an electrostatic discharge to this IC that exceeds the performance ratings of the built-in
electrostatic protection circuit.
 SII Semiconductor Corporation shall bear no responsibility for any patent infringement by a product that
includes an IC manufactured by SII Semiconductor Corporation in relation to the method of using the IC in
that product, the product specifications, or the destination country.
19