s-8460 Seiko Instruments Inc., s-8460 Datasheet - Page 14

• Manufacturer Part Number: s-8460
• Description: Step-up Or Down, Single-coil, Pwm Control Switching Regulator Controller
• Manufacturer: Seiko Instruments Inc.

14
STEP-UP OR DOWN, SINGLE-COIL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
S-8460
Caution The above connections and values will not guarantee correct operation.
5. Output Voltage Adjustment
Standard Circuit
MOS FETs Are Used
The output voltage is externally set in the S-8460. The output voltage can be set and adjusted in the output
voltage setting range (2.5 to 6.0 V) by adding external resistors (R
Temperature gradient can be added by inserting a thermistor in series to R
The output voltage is set as (R
exceed 2 MΩ.
operation like output oscillation.
Set the C
The precision of V
pin (1.0 V ±2.0%) as well as the precision of external resistors R
Waste current flows through R
use, the efficiency decreases. The values of R
When the R
actual condition since the resistors become susceptible to external noise.
A
values, perform sufficient evaluation on the application to be actually used.
C
+
Example : When V
IN
+
fzfb
FB1
so that f = 1/(2 × π × C
and R
SW2
SW1
A capacitor C
OUT
FB2
determined by the resistors R
4.7 μF
SD2
C
C
VL
OUT
values are high, 1 MΩ or higher, evaluation of the influence of the noise is needed in the
BST
= 3.3 V, R
BST
EXT1
LX
EXT2
VL
FB1
T
fzfb
FB1
CPRO
and R
fzfb
should be added in parallel to the external resistor R
+ R
ON/OFF
C
× R
PRO
FB1
FB2
FB2
Seiko Instruments Inc.
FB1
VSS DVSS
= 230 kΩ, R
)/R
. When it is not a negligible value with respect to load current in actual
) is equal to 2 kHz.
FB2
VIN
Figure 13
FB1
, since the FB pin voltage is kept 1.0 V. R
and R
FB1
L
FB2
and R
FB2
CSS
= 100 kΩ, then C
EXT
FB
must therefore be made large.
FB2
C
SS
FB1
is affected by the precision of the voltage at the FB
FB1
and R
and R
SW3
SD1
FB2
FB1
fzfb
R
R
FB2
, and IC power supply voltage V
FB1
FB2
= 330 pF is recommended.
) and a capacitor (C
and R
FB2
C
fzfb
.
+
Before setting these
FB1
+
C
FB1
OUT
to avoid unstable
fzfb
+ R
Rev.2.1
).
I
OUT
FB2
must not
IN
.
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