an8011s Panasonic Corporation of North America, an8011s Datasheet - Page 13

• Manufacturer Part Number: an8011s
• Description: 2-channel Step-down, Step-up, Or Inverting Use Dc-dc Converter Control Ic
• Manufacturer: Panasonic Corporation of North America

Voltage Regulators
[5] Triangular wave oscillation circuit
[6] Dead-time (maximum duty) setting method
• Oscillation frequency setting method
the DTC terminal provides a constant current output through the resistor R
resistor R
oscillation frequency f
voltages depend on the frequency.
the on-period of the output pulse when the power supply is turned on. This prevents the overshoot of the DC-DC
converter output.
Application Notes (continued)
DTC waveform
from the external timing capacitor C
attached timing resistor R
value of the wave V
typical and 0.4 V typical respectively.
following formula;
Out waveform
C
The setting of the dead-time is conducted by adjusting the DTC terminal voltage V
The output duty ratio Du and the DTC terminal voltage V
Pay attention to the peak volue and the trough value of triangular wave because the overshoot and undershoot
When the capacitor C
f
(typ.)
Where I
Because V
f
(typ.)
OSC
OSC
T
The waveform of triangular wave oscillation is obtained by charging and discharging of the constant current I
The peak value of the wave V
The oscillation frequency f
The ouput frequency f
waveform
DTC
t
C
.
1
O
T
1
Du
(typ.)
V
(typ.)
0.67
CTH
DTC
t
2
R
T
CTL
V
V
OSC
R
2
CTL
RT
[Hz]
T
I
V
DTC
are fixed at approximately 1.4 V
t
DTC
V
V
t
Off
ON
OFF
RT
is 200 kHz, the output duty ratio is 0% at V
C
CTH
CTH
T
OUT
T
t
is added in parallel with the external resistor R
1V
ON
.
t
R
OFF
R
(V
is equal to f
I
V
V
DTC
R
O
0.67
DTC
OSC
DTC
CTH
t
CTL
T
R
On
ON
T
T
CTH
is obtained by the
which is connected to CT terminal. The constant current is set by the externally
100 [%]
V
1.04 [V]
and the trough
Figure 6. Dead-time setting method
CHL
100 [%]
OSC
Off
)
since it is PWM-controlled.
V
V
V
ex.) When f
CTH
DTC
CTL
DTC
Figure 5. Triangular wave oscillation waveform
are expressed by the following formula. When the
V
V
DTC
OSC
CTH
CTL
T
Charging
DTC
, V
V
I
DTC
R
REF
DTC
0.42 V, and 100% at V
DTC
, the soft start function gradually extends
t
DTC
1
1.4 V(typ.)
0.4 V(typ.)
200 kHz (R
is adjusted by attaching the external
T
Discharging
DTC
I
t
DTC
2
as shown in figure 6. Since
T
C
CT
FB
DTC
=
20 k , C
V
V
I
DTL
R
RT
RT
V
V
T
DTC
CTH
CTL
1.4 V typ.
0.4 V typ.
PWM
AN8011S
T
0.67 V(typ.)
35 A (typ.)
1.04 [A]
1.35 V.
150 pF),
13
O