s1f78520 Epson Electronics America, Inc., s1f78520 Datasheet - Page 3

• Manufacturer Part Number: s1f78520
• Description: Charge-pump Step Down Regulator With Power Saving Mode
• Manufacturer: Epson Electronics America, Inc.

S1F78520
DESCRIPTIONS FOR THE BLOCK DIAGRAM
(1) Oscillation circuit
This is the circuit to make oscillations by connecting a resistance to the ROSC1 pin and by supplying a constant
current.
(2) Low voltage detection circuit
This circuit makes low voltage detections by monitoring the input voltage through the V
pin. Provision of a
DD
hysteresis width is effective to prevent occurrences of unstable outputs (causing oscillations) while performing
low voltage detecting operations. For setting of the detecting voltages, use of either of the internal voltage
setting fixed to the IC or the external voltage setting pin VSENS is selectable through the VSEL pin.
(3) Voltage dropping type charge pump
The specified voltage is being output by voltage drops effected by the charge pump upon the inputted supply
voltage V
- V
and using the V
potential as the reference voltage. The specified voltage is select-
*
*
*
DD
SS
SS
able (2.5 V or 2.0 V or 1.8 V) through the external pins VO2LV1, VO2LV0.
Also, the voltages are being stabilized by adjusting the switching frequencies of the charge pump. This circuit
can drastically suppress the current consumption under the standby mode (light load).
(4) LDO (series regulator)
It stabilizes the voltage of the levels below the input supply voltage. The specified voltage is selectable (3.3 V
or 2.9 V or 2.5 V) through the external pins VO1LV1, VO1LV0.
(5) Power good detection circuit
This circuit detects the power good signals when the output pins V
and V
are satisfying the specified
OUT1
OUT2
voltage. Delay setting can be made for the power good signals by connecting a capacitor and a resistor to the
external setting pin CPG.
(6) Bias circuit
This circuit generates the reference voltage and reference current which are necessary for this IC.
(7) Shut down
Operations of all the circuits can be interrupted by setting the shut down pin XPOFF to the V
level.
SS
*
<Note> V
= V
, V
, V
= V
, V
, V
*
*
DD
DD
DD2
SS
SS
SS2
SS3
Rev. 1.2
3