Power Management ICs

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 1.08 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

Features

Low voltage operation
1.8 V to 6.0 V
Oscillation frequency
280 kHz to 1.08 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

Standard Circuit

Standard Circuit