STOD2540 STMicroelectronics, STOD2540 Datasheet - Page 8

• Manufacturer Part Number: STOD2540
• Description: PMOLED display power supply
• Manufacturer: STMicroelectronics

Functional description
5
5.1
5.2
5.3
5.4
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Functional description
Boost controller
STOD2540 is a boost converter operating in PFM (pulsed frequency modulation) mode. The
converter monitors the output voltage through the bridge resistor divider R
when the feedback voltage falls below the reference voltage, REF2, the boost switch t
turns ON and the current ramps up. The inductor current is measured by detect the
temperature compensated drain voltage of the boost MOSFET. The boost turns off when its
drain voltage reaches the reference REF1, the main switch remains off until the minimum off
time (300 ns typical) has passed and the feedback voltage is below the reference again. A
maximum ON time of 4 µs prevent the switch t
time.
In order to well calculate the bridge resistors values with a fixed V
can be used:
(V
Adjustable peak inductor current limit
The peak inductor current is monitored by sensing the drain voltage of the switch t
Since it exceeds the temperature compensated and supply voltage compensated reference
REF1, the RS flip flop is reset and t
By connecting a resistance between the pin R
adjusted from 200 mA to 1.1 A (R
connected to V
Enable
The ENABLE pin is a high logic input signal and allows turning on/off the controller without
cutting the input voltage from the boost regulator circuit. With a high input voltage (1.2 V <
V
is present on this pin.
OVP
If the regulation loop is cut, there is no signal at the feedback pin, the PFM controller will
then continue to switch without control and generate an output voltage at the SW, V
V
The over voltage protection (OVP) senses the voltage at the V
exceed the breakdown voltage of the device the controller is automatically turned off.
A hysteresis control enables the device to automatically restart when the output voltage
drops below a 2 V typical value.
O
EN
O
pin exceeding the breakdown value V
/ 1.24) -1 = R
< V
I
+ 0.3 V) on this pin, the device is allowed to work normally. No pull-up or pull down
I
, the default value is 1 A.
1
/ R
2
Doc ID 12204 Rev 10
SET
SW
from 10 kΩ to 100 kΩ). When the pin R
is turned OFF.
BSW
, V
SET
SW
BCAP
to stay ON during a too long period of
and GND, the peak current limit can be
and V
BO
.
CAP
O
pin. When the voltage
, the following formula
1
and R
SET
STOD2540
is directly
2
SW
CAP
and
.
SW
and