The YB1231 is a series of ultra-low noise, low loss (LDO) linear regulators with 2.0% output voltage accuracy. The YB1231 regulator achieves a low voltage drop of 440mV at a load current of 600mA from a 4.5V output, the voltage Ranges from 3.2V to 4.5V with 0.1V per stage (custom voltages are considerable on request). The YB1231 regulator is optimized for use with low ESR and low cost ceramic capacitors, reducing critical board space in handheld devices The current is less than 1µA. Built-in thermal shutdown and short circuit protection provide safe fault operation protection. The YB1231 regulator is available in SOT-23 /SOT-25/SOT-89 packages.
Typical application circuit features „2.0% accuracy output voltage „Output voltage range 3.2V~4.5V„Low noise and low loss „Stable, any load 2.2μF ceramic capacitor (4.5V) about 100μA „440mV loss „Only input and output capacitors „Power saving shutdown mode (<1μA) „Thermal protection shutdown „Built-in soft start „Output short circuit current limit protection „Green package (RoHS) available applications„ PDAs, Palmtops and Notebooks

Absolute Maximum Ratings Supply Voltage …………-0.3V to 7.0V Output Voltage ……………-0.3V to (VIN+0.3V) Output Short-Circuit Duration ………….Unlimited Junction Temperature Range…… …………+150°C Storage Temperature Range………-65°C to +150°C Lead Temperature …………..+250°C Recommended Operating Conditions Input Supply Voltage ………….2V～6.0V Operating Temperature… .......40℃～+85℃ thermal resistance (SOT-23/25, θJC) .......140℃/W thermal resistance (SOT-23/25, θJA) .......280℃/W thermal resistance (SOT- 89, θJC)….46°C/W Thermal Resistance (SOT-89, θJA)….180°C/W Thermal Resistance Power Dissipation (SOT-23/25, PD)…0.4W Thermal Dissipation (SOT- 89, PD)…0.55 W Absolute Maximum Ratings Supply Voltage…………-0.3V to 7.0V Output Voltage…………-0.3V to (VIN+0.3V) Output Short-Circuit Duration………… .Infinite Junction Temperature Range…………+150°C Storage Temperature Range………-65°C to +150°C Lead Temperature …………..+250°C Recommended Operating Conditions Input Supply Voltage …………. 2V～6.0V operating temperature…….40℃～+85℃ Thermal resistance (SOT-23/25, θJC)…….140℃/W thermal resistance (SOT-23/25, θJA)…….280℃ /W Thermal Resistance (SOT-89, θJC)….46°C/W Thermal Resistance (SOT-89, θJA)….180°C/W Thermal Resistance Power Dissipation (SOT-23/25, PD)…0.4 W Thermal Dissipation (SOT-89, PD)… 0.55 W Absolute Maximum Ratings Duration………….Unlimited Junction Temperature Range…………+150°C Storage Temperature Range………-65°C to +150°C Lead Temperature …………..+250°C Recommended Operating Conditions Input Power Voltage………….2V～6.0V Operating temperature…….40℃～+85℃ Thermal resistance (SOT-23/25, θJC)…….140℃/W thermal resistance (SOT-23/25, θJA)…….280℃/W thermal resistance (SOT-89, θJC)…….46℃/W thermal resistance (SOT-89, θJA)…….180℃/W thermal resistance power dissipation (SOT-23/ 25, PD)…0.4W Thermal Power Consumption (SOT-89, PD)…0.55W

Functional block diagram

YB1231 is an ultra-low noise, low quiescent current, low loss linear regulator. It is available in SOT-23/SOT-25/SOT-89 packages for different applications. These units can provide loads up to 600mA. As shown in the functional block diagram, the YB1231 consists of a reference and noise bypass circuit, an error amplifier, an output drive transistor, an internal feedback voltage divider, a thermal sensor, and a short-circuit current limiter. The internal reference is connected to the inverting input of the error amplifier. The error amplifier compares this reference voltage to the feedback voltage and amplifies the difference. If the feedback voltage is lower than the reference voltage, the pass transistor gate is pulled low which allows more current to pass to the output and increases the output voltage. If the feedback voltage is too high, the pass transistor gate is pulled high, allowing less current to flow through the output. The output voltage of these devices varies from 3.2V to 4.5V. Stability The YB1231 is a high performance LDO that emphasizes stability with low output capacitance. The output capacitance is as low as 2.2uf to maintain stability. The output capacitance can also be increased to optimize performance. Unlike many other voltage regulators, the YB1231 will remain stable and No load regulation. The internal P-channel pass transistor YB1231 has a low impedance P-channel MOSFET pass transistor, which offers several advantages over similar designs using PNP transistors, including low operating power and longer battery life. In most cases, the YB1231 Consumes only 100 microamps of quiescent current Output Short-Circuit Current Limit The YB1231 includes a current limiter that monitors and controls the gate voltage of the pass transistor, limiting the output current to about 420mA in a short-circuit output condition, for example. Shutdown The YB1231 also features a low-power active shutdown mode. It has a switch that shuts down the device when disabled. This allows the output capacitor and load to discharge and power down the load. In shutdown mode, internal blocks such as the voltage reference and error amplifier are completely shut down, and quiescent current less than 1 microamp. Thermal Shutdown The Thermal Shutdown feature protects the device from over-temperature conditions. When the junction temperature exceeds +160°C, the thermal sensor signals the shutdown logic to turn off the pass transistor and allow the IC to cool. After the IC's junction temperature drops to +140°C, the thermal sensor turns on the pass-through again. Soft-Start Circuit The YB1231 includes a soft-start circuit to limit the inrush current during turn-on when the power is up, the output capacitor and the output load are charged at a reduced output current. Shortly after initial power-up, the soft-start function is terminated and normal operation of the application is resumed Information Enable/Disable The YB1231 has an active high enable pin that allows the regulator to be enabled. Forcing the enable pin low will disable the regulator and put it into shutdown mode. This pin cannot be left floating as it may cause undetermined state Input/Output Capacitors It is recommended to use a 2.2µF capacitor on the YB1231 input and a 2.2µF capacitor on the output. For high regulation performance, larger input capacitor values and lower esr provide better noise rejection and line transient response. Using bulk output capacitors can improve system output noise, load transient response, stability, and power supply rejection. Low ESR ceramic capacitors provide optimum performance and space savings.