S-8354D20MC-JUFT2G Seiko Instruments, S-8354D20MC-JUFT2G Datasheet - Page 20

• Manufacturer Part Number: S-8354D20MC-JUFT2G
• Description: IC REG SW PWM 2.0V SOT23-5
• Manufacturer: Seiko Instruments
• Type: Step-Up (Boost)r

Specifications of S-8354D20MC-JUFT2G

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 2V
• Frequency - Switching: 50kHz
• 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
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

20
STEP-UP, PWM CONTROL or PWM / PFM SWITCHABLE BUILT-IN TRANSISTOR SWITCHING REGULATOR
S-8353/8354 Series
External Parts Selection
The relationship between the major characteristics of the step-up circuit and the characteristic parameters of the external
parts is shown in Figure 12 .
1. Inductor
2. Diode
The inductance value (L value) has a strong influence on the maximum output current (I
The peak current (I
value is decreased, the efficiency falls causing a decline in the current drive capacity for the switching transistor, and
I
The loss of I
certain L value. Further increasing L value decreases the efficiency due to the loss of the direct current resistance of
the coil. I
A higher oscillation frequency allows selection of a lower L value, making the coil smaller.
The recommended inductances are a 47 μH to 220 μH for A, C, and D types, a 10 μH to 47 μH for H and J types.
Be careful of the allowable inductor current when choosing an inductor. Exceeding the allowable current of the
inductor causes magnetic saturation, much lower efficiency and destruction of the IC chip due to a large current.
Choose an inductor so that I
following equation:
f
Use an external diode that meets the following requirements :
I
OUT
osc
PK
Larger output capacitance
For larger output current ?
= oscillation frequency, V
• Low forward voltage : V
• High switching speed : 50 ns max.
• Reverse voltage :
• Current rate :
=
decreases.
Figure 12 Relationship between Major Characteristics of Step-up Circuit and External Parts
I 2
OUT
OUT
(
PK
V
also decreases.
f
OUT
OSC
by the switching transistor decreases by increasing L and the efficiency becomes maximum at a
Smaller inductance
PK
+
Smaller direct current resistance of inductor
•
L
V
) increases by decreasing L value and the stability of the circuit improves and I
D
−
V
IN
PK
V
I
)
D
PK
F
OUT
≅
does not exceed the allowable current. I
(A)
< 0.3 V
or more
0.4 V.
+ V
F
or more
At PFM control
Seiko Instruments Inc.
For higher efficiency ?
At PWM control
PK
in discontinuous mode is calculated by the
Larger inductance
For smaller ripple voltage ?
Larger output capacitance
OUT
) and efficiency (η).
OUT
Rev.3.0
increases. If L
(17)
_00