s-8337aaca-t8t1g Seiko Instruments Inc., s-8337aaca-t8t1g Datasheet - Page 20

• Manufacturer Part Number: s-8337aaca-t8t1g
• Description: Step-up, 1.2 Mhz High-frequency, Pwm Control Switching Regulator Controller
• Manufacturer: Seiko Instruments Inc.

20
STEP-UP, 1.2 MHz HIGH-FREQUENCY, PWM CONTROL SWITCHING REGULATOR CONTROLLER
S-8337/8338 Series
6. Short-circuit protection delay time setting capacitor (CSP)
7. Output voltage setting resistors (RFB1, RBF2)
8. Phase compensation setting resistor and capacitor (RZ, CZ)
With the S-8337/8338 Series, the short-circuit protection delay time can be set to any value by an
external capacitor. Connect the capacitor across the CSP and VSS pins. Select the capacitance by
using the following equation and referring to Figure 14 . However, the following equation and figure
assume that the capacitor value is the desired value and show the theoretical values when the IC is in
the typical conditions. Note that fluctuations of capacitor and IC are not considered.
C
With the S-8337/8338 Series, the output voltage can be set to any value by external divider resistors.
Connect the divider resistors across the V
can be calculated by this equation.
Connect divider resistors RFB1 and RFB2 as close to the IC to minimize effects from of noise. If noise
does have an effect, adjust the values of RFB1 and RFB2 so that R
CFB connected in parallel with RFB1 is a capacitor for phase compensation. Select the optimum
value of this capacitor at which the stable operation can be ensured from the values of the inductor
and output capacitor.
The S-8337/8338 Series needs appropriate compensation for the voltage feedback loop to prevent
excessive output ripple and unstable operation from deteriorating the efficiency. This compensation is
implemented by connecting RZ and CZ in series across the CC and VSS pins.
high-frequency gain for a high-speed transient response. CZ sets the pole and zero of the error
amplifier and keeps the loop stable. Adjust RZ and CZ, taking into consideration conditions such as
the inductor, output capacitor, and load current, so that the optimum transient characteristics can be
obtained.
V
OUT
SP
[μF]
=
(R
≅
FB1
t
R
PRO
+ R
FB2
[ms]
FB2
1.0
)
•
2
•
10
− 3
Seiko Instruments Inc.
OUT
and VSS pins. Because V
120
100
80
60
40
20
0
0
0.05
Figure 14 C
FB1
0.10
C
+ R
SP
FB
[μF]
FB2
SP
= 1 V, the output voltage
0.15
vs. t
< 100 kΩ.
PRO
0.20
Rev.3.1
RZ sets the
0.25
_00