S-8340A30AFT-T2-G Seiko Instruments, S-8340A30AFT-T2-G Datasheet - Page 17

• Manufacturer Part Number: S-8340A30AFT-T2-G
• Description: IC REG SW 600KHZ 3.0V 8-TSSOP
• Manufacturer: Seiko Instruments
• Type: Step-Up (Boost)r

Specifications of S-8340A30AFT-T2-G

• Internal Switch(s): No
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 3V
• Frequency - Switching: 600kHz
• Voltage - Input: 0.9 ~ 6 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-TSSOP
• Power - Output: 300mW
• Output Voltage: 3 V
• Operating Temperature Range: - 40 C to + 85 C
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

STEP-UP, 600 kHz, PWM CONTROL OR PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.4.0
Operation
1. Switching Control Method
2. Soft-Start Function
1. 1 PWM Control (S-8340 Series)
1. 2 PWM/PFM Switching Control (S-8341 Series)
The S-8340 Series is a DC-DC converter using a pulse width modulation method (PWM).
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 82% corresponding to each
load current in the S-8340 Series. The ripple voltage generated from switching can thus be eliminated easily
through a filter. When the pulse width is 0% (when no load is applied or the input voltage is high), pulses are
skipped and the current consumption is low.
The S-8341 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.
The S-8341 Series operates under PWM control with the pulse duty changing from 27 to 82% (A and B types) and
from 21 to 82% (C and D types) in a high output load current area.
The S-8341 Series operates under PFM control with the pulse duty fixed at 27% (A and B types) and at 21% (C and
D types) in a low load current area, 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.), and input and output voltage values. The S-8341 Series is an especially highly efficient
DC-DC converter at an output load current around 1 mA.
The S-8340/8341 Series has a built-in soft-start circuit.
This circuit enables the output voltage (V
overshooting of the output voltage and the rush current from the power supply when the power is switched on or the
ON/OFF pin is changed to “H”.
Generally, a rush current flows to an output capacitor through an inductor and a diode in the step-up circuit
immediately after the power is turned on as shown in Figure 9. Note that the soft-start function of this IC, however,
does not limit this current.
_00
Figure 9 Waveforms of Output Voltage and Rush Current at Soft-Start
O u t p u t vo lta g e
R u s h cu r re n t
(0. 5 A /d iv )
(1 V /d iv )
1 .5 A
3 V
0 V
0 A
S -8 3 40 A 3 3 A F T (V
OUT
Seiko Instruments Inc.
) to rise gradually over the specified soft-start time (t
t (2 m s /d iv )
IN
= 0 → 1 .9 V , R
L
= 3 0 0 k Ω )
S-8340/8341 Series
SS
) to suppress the
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