s-8521b51mc-aukt2g Seiko Instruments Inc., s-8521b51mc-aukt2g Datasheet - Page 14

• Manufacturer Part Number: s-8521b51mc-aukt2g
• Description: Step-down, Pwm Control Or Pwm / Pfm Switchable Switching Regulator Controller
• Manufacturer: Seiko Instruments Inc.

14
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
S-8520 / 8521 Series
2. Soft start function
3.
The S-8520 / 8521 Series comes with a built-in soft start circuit. This circuit enables the output voltage
(V
However, the soft start function of this IC is not able to perfectly prevent a rush current from flowing to the
load (Refer to Figure 8 ). Since this rush current depends on the input voltage and load conditions, we
recommend that you evaluate it by testing performance with the actual equipment.
This pin deactivates or activates the step-down operation.
When the
switching transistor to go off. All the internal circuits stop working, and substantial savings in current
consumption are thus achieved.
The
internally, please avoid operating the pin in a floating state. Also, try to refrain from applying a voltage of
0.3 to 1.8 V to the pin, lest the current consumption increase. When this
leave it coupled to the VIN pin.
ON
ON/
ON
OUT
ON
/
OFF
) to rise gradually over the specified soft start time (t), when the power is switched on or when the
OFF
ON
/
OFF
“H”
/
“L”
OFF
/
OFF
pin remains at the "H" level. This prevents the output voltage from overshooting.
pin (Shutdown pin)
ON
pin
Figure 9
/
Figure 8 Waveforms of output voltage and rush current at soft start
pin is configured as shown in Figure 9 . Since pull-up or pull-down is not performed
Rush current
OFF
CR Oscillation Circuit
[0.5 A/div]
[1 V/div]
pin is set to "L", the V
Deactivated
V
Activated
VIN
OUT
Table 8
VSS
1.5 A
3 V
0 V
0 A
Output Voltage
Seiko Instruments Inc.
Set value
IN
V
voltage appears through the EXT pin, prodding the
SS
t [1 ms/div]
S-8520A33MC (V
IN
: 0→4.0 V)
ON
/
OFF
pin is not used,
Rev.8.3
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