S-8521A25MC-AXK-T2 Seiko Instruments, S-8521A25MC-AXK-T2 Datasheet - Page 13

• Manufacturer Part Number: S-8521A25MC-AXK-T2
• Description: DC/DC Switching Regulators 2.5V 60uA Step-Down
• Manufacturer: Seiko Instruments

Specifications of S-8521A25MC-AXK-T2

• Output Voltage: 2.5 V
• Output Current: 120 mA
• Input Voltage: 2.5 V to 10 V
• Duty Cycle (max): 100 %
• Switching Frequency: 180 KHz
• Mounting Style: SMD/SMT
• Package / Case: SOT-23-5
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Rev.9.0
1. Switching control method
Operation
1. 1 PWM control (S-8520 Series)
1. 2 PWM / PFM switching control (S-8521 Series)
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
The S-8520 Series is a DC-DC converter using a pulse width modulation method (PWM) and features a low
current consumption.
In conventional PFM DC-DC converters, pulses are skipped when the output load current is low, causing a
fluctuation in the ripple frequency of the output voltage, resulting in an increase in the ripple voltage.
The switching frequency does not change, although the pulse width changes from 0 to 100% corresponding to
each load current. The ripple voltage generated from switching can thus be removed easily through a filter
because the switching frequency is constant. And the ripple voltage will be skipped to be low current
consumption when the pulse width is 0% or it is no load, input current voltage is high.
S-8521 Series is a DC-DC converter that automatically switches between a pulse width modulation method
(PWM) and a pulse frequency modulation method (PFM), depending on the load current, and features low
current consumption.
The S-8521 Series operates under PWM control with the pulse width duty changing from 25 to 100% in a high
output load current area.
The S-8521 Series operates under PFM control with the pulse width duty fixed at 25%, and pulses are skipped
according to the load current. The oscillation circuit thus oscillates intermittently so that the resultant lower self
current consumption prevents a reduction in the efficiency at a low load current. The switching point from PWM
control to PFM control depends on the external devices (coil, diode, etc.), input voltage and output voltage.
The S-8521 Series is an especially highly efficient DC-DC converter at an output current around 100 μA.
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Seiko Instruments Inc.
S-8520/8521 Series
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