s-8521b51mc-aukt2g Seiko Instruments Inc., s-8521b51mc-aukt2g Datasheet - Page 23

• Manufacturer Part Number: s-8521b51mc-aukt2g
• Description: Step-down, Pwm Control Or Pwm / Pfm Switchable Switching Regulator Controller
• Manufacturer: Seiko Instruments Inc.

Rev.8.3
Application Circuits
1. External adjustment of output voltage
The voltage accuracy of the OUT cannot be made higher than the output voltage accuracy (V
the IC itself, without adjusting the R
the output voltage value (V
immune to deviations in the absolute accuracy of R
particular, to suppress the influence of deviations in R
the OUT, the R
The S-8520 / 8521 Series allows you to adjust the output voltage or to set the output voltage to a value
over the preset output voltage range (6 V) of the products of this series, when external resistances (R
and R
can be obtained by inserting a thermistor or other element in series with R
Caution The above connection diagram and constant will not guarantees successful operation.
The S-8520 / 8521 Series have an internal impedance of R
pin, as shown in Figure 14 .
Therefore, OUT (the output voltage) is determined by the output voltage value (V
Series, and the ratio of the parallel resistance value of external resistance (R
(R
The voltage accuracy of the OUT set by resistances (R
voltage accuracy (V
use and the absolute value deviations of internal resistances (R
Let us designate the maximum deviations of the absolute value of R
respectively, the minimum deviations by R
deviations of the absolute value of R
Then, the minimum deviation value OUTmin and the maximum deviation value OUTmax of the OUT are
expressed by the following equations:
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
1
+R
OUT=V
OUT min.=V
OUT max.=V
_00
2
B
) of the IC, to external resistance (R
), and capacitor (C
OUT
Perform through evaluation using the actual application to set the constant.
+
−
A
+V
and R
OUT
OUT
OUT
ON
×0.976+V
×1.024+V
×R
OUT
/
B
OFF
VIN
A
must be limited to a much smaller value than that of R
÷(R
±2.4 %), but also by the absolute precision of external resistances (R
OUT
C
PWM/PFM switching
Oscillation
B
) are added, as illustrated in Figure 14 . Moreover, a temperature gradient
//
OUT
EXT
OUT
PWM control or
circuit
) of the IC are brought to one other, the more the output voltage remains
*1
control circuit
(R
×0.976×R
×1.024×R
1
A
+ R
and R
S-8520/8521Series
voltage source
1
2
with soft start
))
Reference
and R
A
A
B
min.÷(R
VSS
A
A
max.÷(R
min and R
). The output voltage is expressed by the following equation:
involved. The closer the voltage value of the output OUT and
Seiko Instruments Inc.
2
Figure 14
in the IC by (R
+
−
A
and R
B
max//(R
B
1
min//(R
and R
B
R
R
min, respectively, and the maximum and minimum
1
2
B
A
and the absolute value of R
VOUT
and R
1
1
2
1
+R
+R
in the IC, a major contributor to deviations in
and R
2
1
2
1
) max.)
+R
) min.)
B
and R
) is not only affected by the IC's output
2
2
) max and (R
D1
between the VOUT pin and the VSS
2
) in the IC.
A
and R
A
and R
1
and R
S-8520 / 8521 Series
B
) and internal resistances
B
OUT
B
1
by R
C
.
+R
C
) of the S-8520 / 8521
1
2
2
and R
in the IC.
) min, respectively.
A
R
R
max and R
A
B
OUT
2
in the IC. In
A
+
−
and R
±2.4 %) of
OUT
B
max,
B
) in
23
A