tcv7100f TOSHIBA Semiconductor CORPORATION, tcv7100f Datasheet - Page 6

• Manufacturer Part Number: tcv7100f
• Description: Buck Dc-dc Converter Ic
• Manufacturer: TOSHIBA Semiconductor CORPORATION

Application Notes
Inductor Selection
appropriate inductor, taking the input voltage range into account.
Setting the Output Voltage
based on the reference voltage of the error amplifier (0.8 V typ.), which is connected to the Feedback pin, V
R
capacitance at the V
and R
values should be selected to meet this relationship: R
of C
load conditions, C
FB1
*: Generally, ΔI
The inductance required for inductor L can be calculated as follows:
When V
A resistive voltage divider is connected as shown in Figure 3 to set the output voltage; it is given by Equation 3
C
FB1
FB1
output current of the TCV7100F is 2.5 A, ΔI
rating greater than the peak output current of 2.9 A. If the inductor current rating is exceeded, the inductor
becomes saturated, leading to an unstable DC-DC converter operation.
should be up to 30 kΩ or so, because an extremely large-value R
FB2
L
L
V
OUT
and C
and C
=
=
=
= 1.87 μH
.
IN
V
V
800kHz
f
f
IN
IN
OSC
OSC
5
= 5 V and V
=
=
V
FB2
FB2
0
−
−
V
.
−
FB
8
V
V
Δ ⋅
Δ ⋅
3.3
FB1
OUT
OUT
⋅
V
are intended to improve the high-frequency characteristics of the control loop. Component
L
should be 500 pF to 1000 pF. If the switching waveform is unstable depending on the output
0.75A
I
I
⋅
L
L
×
FB
⎛
⎜
⎜
⎝
should be set to approximately 30% of the maximum output current. Since the maximum
V
1
⎛
⎜
⎜
⎝
and C
1
+
⋅
⋅
pin. It is recommended that resistors with a precision of ±1% or higher be used for R
+
V
V
R
R
OUT
V
V
⋅
OUT
OUT
R
R
3.3
FB2
FB1
IN
IN
5
FB2
FB1
FB2
V
V
= 3.3 V, the required inductance can be calculated as follows. Be sure to select an
⎞
⎟
⎟
⎠
············· (1)
⎞
⎟
⎟
⎠
············ (2)
may help improve its stability.
·········· (3)
V
V
f
ΔI
OSC
IN
OUT
L
L
: Inductor ripple current (A)
: Input voltage (V)
should be 0.75 A or so. The inductor should have a current
: Oscillation frequency = 800 kHz (typ.)
I
L
: Output voltage (V)
FB1
6
0
Figure 3 Output Voltage Setting Resistors
/R
Figure 2 Inductor Current Waveform
T =
FB2
f
OSC
V
= C
1
L
FB
X
FB2
FB1
/C
FB1
incurs a delay due to parasitic
. As a guide, the series capacitance
V
OUT
T
ON
TCV7100F
=
2008-06-10
Τ
⋅
V
V
OUT
IN
FB
FB1
.