Datasheet

Function description ST1S14
10/46 DocID17977 Rev 2
4 Function description
The ST1S14 is based on a “peak current mode”, constant frequency control. As a
consequence the intersection between the error amplifier output and the sensed inductor
current generates the control signal to drive the power switch.
The main internal blocks shown in the block diagram in Figure 3 are:
• A fully integrated sawtooth oscillator with a typical frequency of 850 kHz
• A transconductance error amplifier
• A high side current sense amplifier to track the inductor current
• A pulse width modulator (PWM) comparator and the circuitry necessary to drive the
internal power element
• Soft-start circuitry to decrease the inrush current at power-up
• Current limitation circuit based on the pulse-by-pulse current protection with frequency
divider based on FB voltage and the hiccup protection
• Bootstrap circuitry to drive the embedded N-MOS switch
• A multi input inhibit block for standby operation
• A circuit to implement the thermal protection function
Figure 3. Device block diagram
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