S-8351A33MC-J2ST2G Seiko Instruments, S-8351A33MC-J2ST2G Datasheet - Page 16

• Manufacturer Part Number: S-8351A33MC-J2ST2G
• Description: IC REG SW 100KHZ 3.3V SOT23-5
• Manufacturer: Seiko Instruments
• Type: Step-Up (Boost)r

Specifications of S-8351A33MC-J2ST2G

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 3.3V
• Frequency - Switching: 100kHz
• Voltage - Input: 0.9 ~ 10 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: SOT-23-5, SC-74A, SOT-25
• Power - Output: 250mW
• Output Voltage: 3.3 V
• Input Voltage: 10 V
• Duty Cycle (max): 75 %
• Switching Frequency: 100 KHz
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

16
STEP-UP, BUILT-IN / EXTERNAL FET PFM CONTROL SWITCHING REGULATOR / SWITCHING REGULATOR CONTROLLER
S-8351/8352 Series
Operation
1. Step-up DC-DC Converter
Figure 15 Output Current (I
The S-8351/8352 Series is a DC-DC converter that uses a pulse frequency modulation method (PFM) and features
low current consumption. This series is an especially efficient DC-DC converter at an output current of 100
lower.
In conventional fixed-duty PFM DC-DC converters, although a low duty ratio allows a lower ripple voltage when the
current load is light, the efficiency is decreased when the output load current is large. Conversely, a high duty ratio
increases the output load current and efficiency, but increases the ripple voltage when the output load current is low.
In the A, B, and D types, the duty ratio is automatically switched 75% when the output load current is high to secure
the load drive capability and 50% when the output load current is low to control the load drive capability to decrease
pulse skipping. This suppresses a drop in the ripple frequency, enabling control of the increase in the ripple voltage.
The C type adopts a 75% fixed-duty PFM method. The ripple voltage increases more than that of the duty switching
type with the load is low, but the efficiency is better.
In the A, B, and D types, the duty ratio is not rapidly changed, but rather smoothly switched in the intermediate area
between 50% and 75%. Therefore, fluctuation of the ripple voltage caused by duty switching is minimized. Figures
15, 16 show the ripple voltage characteristics versus the output current.
These figures show that the ripple voltage decreases as the output load current (I
The ripple voltage becomes particularly small when I
100
S-8351A30MC
90
80
70
60
50
40
30
20
10
0
Characteristics
0
20
40
I
OUT
OUT
) vs. Ripple Voltage (V
[mA]
60
V
V
IN
IN
Ta = 25°C
= 1.5 V
= 2 V
80
Seiko Instruments Inc.
100
OUT
rp-p
)
is in the coil current discontinuous region of 20 mA or less.
Figure 16 Output Current (I
140
120
100
S-8351A50MC
80
60
40
20
Characteristics
0
0 20 40 60 80 100 120 140 160 180
OUT
I
OUT
OUT
) changes from large to small.
) vs. Ripple Voltage (V
[mA]
V
V
IN
IN
Ta = 25°C
= 2 V
= 3 V
Rev.3.0
rp-p
μ
_00
A or
)