STOD1812 View Datasheet(PDF) - STMicroelectronics

Part Name

Description

View to exact match

STOD1812

Power supply for PMOLED display panel

STMicroelectronics 

Functional description

5

Functional description

STOD1812

5.1

Boost controller

STOD1812 is a boost converter operating in PFM (pulsed frequency modulation) mode. The

converter monitors the output voltage through the bridge resistor divider R1 and R2, and

when the feedback voltage falls below the feedback voltage, the boost switch tSW turns on

and the inductor current ramps up. The inductor current is measured by detecting the

temperature compensated drain voltage of the boost MOSFET. The boost turns off when its

drain voltage reaches the internal reference, the main switch remains off until the minimum

off time has passed and the feedback voltage is below the reference again. A maximum ON

time prevents the switch tSW from staying ON for an excessively long period.

In order to calculate the values of the bridge resistors with a fixed VO, the following formula

can be used:

VO

R1

-1 =

1,21

R2

5.2

Enable

The ENABLE pin is a logic input signal that turns on the controller when the voltage on this

pin is equal to or higher than 1.2 V. When the voltage is at or below 0.4 V the STOD1812

goes into shutdown mode. In this case, the true-shutdown switch is turned off and the

overall power consumption is reduced to 0.1 µA. No pull-up or pull-down is present on this

pin.

5.3

Efficiency

The total consumption of some PMOLED displays can be as low as 1 mA. In order to

increase the battery life of the device, the STOD1812 offers high efficiency over a wide

range of output load current and input voltages. See typical application efficiency

performance in Section 8 on page 11.

5.4

Under voltage lockout (UVLO)

The minimum supply voltage is 2.5 V, under which the undervoltage lockout circuit operates

with a typical threshold of 2.3 V.

8/19

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