illustrate
The YB1231 is a series of ultra-low noise, low dropout (LDO) linear regulators with 2.0% output voltage accuracy. The YB1231 type regulator outputs 4.5 V at a 600 mA load current voltage range from 3.2V to
4.5 volts, 0.1 volts per level (custom voltages are considerable upon request).
The YB1231 regulator is optimized to use low ESR and low cost ceramic capacitors, reducing the number of boards in the critical space of handheld devices. This YB1231 requires only a 2.2µF output capacitor and consumes less than 1µA at any load and shutdown
model.
Built-in thermal shutdown and short protection provide safe fail-safe operation. Packaging is available in YB1231 Regulatory Agency SOT-23 /SOT-25/SOT-89.
„Features„ 2.0% Accuracy Output Voltage Output Voltage Range 3.2V~4.5V Low Noise Low Dropout Stable with 2.2μF Ceramic Capacitors for Any Load Typical Output Current: 600MA Low Quiescent Current: ~100μA at 600MA Load (4.5V), 440mV Voltage Drop only input and output capacitors are required for power saving shutdown mode (<1µA) „Thermal protection shutdown „Built-in soft-start output short circuit current limit protection available in green packaging (RoHS)
„Applications„ PDAs, PDAs and Laptops DSC, Mobile Phone Camera Modules PCMCIA Cards, PC Cameras USB-based Portable Devices (MP3, PMP) GSM/GPRS/3G RF Transceiver Modules Wireless LAN Bluetooth Portable Radio

Ordering Information Marking Information Absolute Maximum Ratings (Note 1)
Supply voltage……………………-0.3V to 6V
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 (Note 2)
Input Supply Voltage…………2.0V to 5.5V Operating Temperature……..-40°C to +85°C
Formation heat (Note 3)
Thermal resistance (SOT-23/25, θja) 280 degrees Celsius/w
Thermal resistance (SOT-89, θja) 180 degrees Celsius/w
Internal power consumption (SOT-23/25, PD). 0.4W
Internal power consumption (SOT-89, PD)...0.55W
Note:
1. Exceeding these ratings may damage the device.
2. Equipment is not guaranteed to operate outside of its operating conditions.
three. θja is measured in free air at Ta = 25°C on a plate with low effective thermal conductivity.

Function description
The YB1231 is an ultra-low noise, low quiescent current, low attenuation linear regulator. It is provided by SOT-23.
SOT-25/SOT-89 different packaging applications. These devices can provide loads up to 600mA. As shown in the functional block diagram, YB1231 includes reference and noise bypass circuits, error amplifier, output drive transistor, internal feedback voltage divider, thermal sensor, and short-circuit current limiter. Internal reference is connected to the inverting input of the wrong amplifier. This error amplifier compares this reference 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. This allows more current through the output to increase the output voltage. If the feedback voltage is too high, the pass transistor gate is pulled high, allowing less current to pass to the output. Parts are provided with preset output voltages ranging from 3.2V to 4.5V.
stability

YB1231 is a high performance LDO.
Stable capacitors with emphasis on low yield. It can maintain stable output capacitance as low as 2.2μF.
The output capacitor can also be added to optimize performance. The YB1231 will remain stable, no load regulation, unlike many other voltage regulators.
The internal P-channel pass transistor YB1231 has low impedance characteristics.

P-channel MOSFET pass transistor. This design has several advantages over similar designs using PNP pass transistors, including lower operating power and longer battery life. The YB1231 consumes only 100 microamps of quiescent current condition.
Output Short-Circuit Current Limit The YB1231 includes a current limiter that monitors the gate voltage of the pass transistor, limiting the output current to about 420mA, for example, in a short-circuit output condition.
YB1231 also has a low power active shutdown mode. It has a switch to turn off the device when disabled. This allows the output capacitor and load to discharge and power down the load. In shutdown mode, internal functional blocks, such as the voltage reference and error amplifier, are completely shut down and the quiescent current is less than 1 µA.
A thermal shutdown feature prevents equipment from operating in excessive temperature conditions. When the junction temperature exceeds +160°C, the thermal sensor signals the shutdown logic to turn off the pass transistor, allowing the IC to cool down. The thermal sensor turns on again after the IC turns on and the transistor junction temperature drops to +140°C.
Soft start circuit
The YB1231 includes a soft-start circuit to limit inrush current when turned on. Up during power-up, the output capacitor and output load are charged with a reduced output current. Shortly after initial power-up, the soft-start function is terminated and normal operation is restored.
App info enable/disable
The YB1231 has an active high enable that allows the regulator to be enabled. Forcing the enable pin low disables the regulator and puts it into shutdown mode. This pin cannot be left as it may lead to state.
2.2µF capacitors are recommended for input/output capacitors.
On the YB1231 input and a 2.2µF capacitor on the output. For high regulation performance, larger input capacitor values with low ESR provide better noise rejection and line transient response. The output noise, load transient response, stability and power supply rejection are improved with large output capacitors.
Low ESR ceramic capacitors provide optimum performance and space savings.