TB7101F(T5L1.2,F) , TB7101F(T5L1.5,F)
TB7101F(T5L1.8,F) , TB7101F(T5L2.5,F)
TB7101F(T5L3.3,F)
Electrical Characteristics Common to All Products
2007-09-06
10
When a pulse test is carried out, Tj = 25°C is the standard condition in the measurements for each item.
Any drift in the electrical characteristic due to a rise in the junction temperature of the chip may be disregarded.
Application Circuit Example
Figure 1: TB7101F application circuit example
Component constants
The following values are given only for your reference and may need tuning depending on your input/output conditions and board
layout.
C
IN
: Input smoothing capacitance of 10
μ
F
(multilayer ceramic capacitor JMK212BJ106KG, manufactured by Taiyo Yuden Co., Ltd.)
C
OUT
: Output smoothing capacitance of 10
μ
F
(multilayer ceramic capacitor JMK212BJ106KG manufactured by Taiyo Yuden Co., Ltd.)
L: Inductor3.3
μ
H (@ V
IN
= 5 V, V
OUT
= 3.3 V); CDRH4D28C/LD series, manufactured by Sumida Corporation
How to use
Setting the Inductance
The required inductance can be calculated by using the following equation:
V
I
f
Δ
IN
OUT
V
L
OSC
OUT
IN
V
V
L
=
… (1)
V
IN
: Input voltage (V) f
OSC
: Oscillation frequency (Hz)
V
OUT
: Output voltage (V)
Δ
I
L
: Inductor ripple current (A)
* Generally,
Δ
I
L
should be set to 30% to 40% of the maximum output current. For the TB7101F, set
Δ
I
L
to 0.3 A, as its
maximum current [I
LX(MAX)
] is 1 A (min). Therefore select an inductor whose current rating is no lower than the
peak switch current [1.15 A (min)] of the TB7101F. If the current rating is exceeded, the inductor becomes
saturated, leading to an unstable DC-DC converter operation.
If V
IN
= 5 V and V
OUT
= 3.3 V, the required inductance can be calculated as below. Be sure to select an inductor
with an optimum constant by taking V
IN
variations into consideration.
TB7101F(T5L*.*,F)
V
OUT
PGND
SGND
EN
V
IN
C
OUT
V
OUT
GND
L
C
IN
GND
L
X
V
IN