s-8460 Seiko Instruments Inc., s-8460 Datasheet - Page 15

• Manufacturer Part Number: s-8460
• Description: Step-up Or Down, Single-coil, Pwm Control Switching Regulator Controller
• Manufacturer: Seiko Instruments Inc.

Rev.2.1
Precautions
• Mount the external capacitors, diode, coil, and other peripheral parts as close to the IC as possible, and make a one-
• Normally SW1 and SW2 do not turn on at the same time. If external N-channel transistors have much different
• Characteristics ripple voltage and spike noise occur in IC containing switching regulators. Moreover rush current flows
• When the input voltage is high and the output current is low, pulses with a low duty ratio may appear, and then the 0%
• According to the input voltage and the load condition the oscillation frequency of the EXT1 to EXT3 may become an
• No parts other than a capacitor (C
• A 4.7 μF ceramic capacitor should be connected to the VL pin.
• The overload protection circuit of the IC starts working by detecting the time for maximum duty. In choosing the
• The oscillation frequency of the EXT1 and EXT2 may vary in some voltage range and load condition depending on
• If the VOUT pin is short-circuited to VSS, the protection circuit starts to operate before the integral protection time t
• When the temperature is high and the load is 0 to 1 μA, the voltage of the EXT1 to EXT3 pins is held “L” and the
• Make sure that dissipation of the switching transistor especially at high temperature will not surpass the power
• Switching regulator performance varies depending on the design of PCB patterns, peripheral circuits and parts.
• Do not apply an electrostatic discharge to this IC that exceeds the performance ratings of the built-in electrostatic
• SII claims no responsibility for any disputes arising out of or in connection with any infringement by products including
STEP-UP OR DOWN, SINGLE-COIL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
point grounding.
characteristics (input capacitance, Vth, etc.) among them, however, they may turn on at the same time, and through
current flows. Select transistors with similar characteristics.
at the time of a power supply injection. Because these largely depend on the coil, the capacitor and impedance of
power supply used, fully check them using an actually mounted model.
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.
integer fraction of 300 kHz.
parts, make sure that the overcurrent caused by load short-circuiting will not exceed the power dissipation of the
switching transistors, diodes, and the inductor.
input voltage.
passes.
output voltage V
dissipation of the package.
Thoroughly evaluate the actual device when setting. When using parts other than those which are recommended,
contact the SII marketing department.
protection circuit.
this IC of patents owned by a third party.
_00
OUT
increases.
The operation returns to normal when the load of 1 μA or more is attached.
VL
) and a Schottky diode (SD2) can be connected to the VL pin.
Seiko Instruments Inc.
S-8460
15
PRO