Rev.1.0
_02
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL, PWM
CONTROL SWITCHING REGULATOR CONTROLLER
S-8333 Series
The S-8333 Series is a CMOS step-up switching regulator which mainly consists of a
reference voltage circuit, an oscillator, an error amplifier, a PWM controller, an under voltage
lockout circuit (UVLO), and a timer latch short-circuit protection circuit. Because its minimum
operating voltage is as low as 1.8 V, this switching regulator is ideal for the power supply of
an LCD or for portable systems that operate on a low voltage. The internal oscillation
frequency can be set up to 1.133 MHz, via the resistor connected to the ROSC pin.
The maximum duty ratio of PWM control can be controlled by the resistor connected to the
RDuty pin. The soft-start function at power application is accomplished by combining the
reference voltage control and maximum duty control methods. Even if the voltage of the FB
pin is retained lower than the reference voltage due to the factor outside the IC, the output
voltage is raised by controlling the maximum duty. The phase compensation and gain value
can be adjusted according to the values of the resistor and capacitor connected to the CC
pin. Therefore, the operation stability and transient response can be correctly set for each
application. The reference voltage accuracy is as high as 1.0 V
±1.5%,
and any voltage can
be output by using an external output voltage setting resistor.
In addition, the delay time of the short-circuit protection circuit can be set by using the
capacitor connected to the CSP pin. If the maximum duty condition continues because of
short-circuiting, the capacitor externally connected to the CSP pin is charged, and oscillation
stops after a specific time. The short-circuit protection function is cancelled when the power
supply is raised to the UVLO release voltage after it has been lowered to the UVLO detection
voltage. A ceramic capacitor or a tantalum capacitor is used as the output capacitor,
depending on the setting. This controller IC allows various settings and selections and
employs a small package, making it very easy to use.
Features
•
•
•
•
•
Low voltage operation:
1.8 V to 6.0 V
Oscillation frequency:
286 kHz to 1.133 MHz (selectable by external resistor)
Maximum duty:
47 to 88.5% (selectable by external resistor)
Reference voltage:
1.0 V
±1.5%
UVLO (under-voltage lockout) function:
Detection voltage can be selected from between 1.5 V and 2.3 V in 0.1 V steps.
Hysteresis width can be selected from between 0.1 V and 0.3 V in 0.1 V steps.
Timer latch short-circuit protection circuit:
Delay time can be set using an external capacitor.
Soft-start function:
Soft-start time can be selected in three steps, 10 ms, 15 ms, and 20 ms.
Both reference voltage control and maximum duty control methods are applied
Phase compensation external setting:
Control is possible via the resistor connected between the CC and GND pins and
capacitor
Small package:
SNT-8A, 8-Pin TSSOP
•
•
•
•
Applications
•
Power supplies for LCDs and CCDs
•
Power supplies for portable equipment
Packages
Package Name
SNT-8A
8-Pin TSSOP
Package
PH008-A
FT008-A
Drawing Code
Tape
PH008-A
FT008-E
Reel
PH008-A
FT008-E
Seiko Instruments Inc.
1
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
Rev.1.0
_02
S-8333 Series
Pin Assignment
Table 1
Pin No.
1
8
7
6
5
SNT-8A
Top view
1
2
3
4
Pin Name
CC
FB
CSP
VIN
EXT
VSS
ROSC
RDuty
Functions
Error amplifier circuit output phase
compensation pin
Output voltage feedback pin
Short-circuit protection delay time setting pin
Power supply input pin
External transistor connection pin
GND pin
Oscillation frequency setting resistor
connection pin
Maximum duty setting resistor connection pin
2
3
4
5
6
7
Figure 2
8
Table 2
Pin No.
1
8
7
6
5
8-Pin TSSOP
Top view
1
2
3
4
Pin Name
CC
FB
CSP
VIN
EXT
VSS
ROSC
RDuty
Functions
Error amplifier circuit output phase
compensation pin
Output voltage feedback pin
Short-circuit protection delay time setting pin
Power supply input pin
External transistor connection pin
GND pin
Oscillation frequency setting resistor
connection pin
Maximum duty setting resistor connection pin
2
3
4
5
6
7
Figure 3
8
Seiko Instruments Inc.
5
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