ST STOD1812 User Manual

Power supply for PMOLED display panel

Features

■ Synchronous step-up converter

■ Input voltage range from 2.5 V to 5.5 V

■ Maximum output current 120 mA

■ Efficiency: 75 % at I

I

= 30 mA - 120 mA

O

■ Switching at 1.2 MHz in typical application

conditions

■ Enable pin for shutdown mode

■ True load disconnect

■ Soft-start to limit inrush current

■ UVLO protection

■ Adjustable output voltage up to 20 V

■ Low quiescent current: < 1 µA in shutdown

mode

■ Over-temperature protection

■ Package: DFN10L 3x3 mm, 0.8 mm

■ Operating junction temperature range:

-40 °C to 125 °C

Applications

■ Passive matrix OLED power supplies

■ Mobile phones

■ PDAs

■ Camcorders

■ Digital still cameras

= 10 mA - 30 mA; 85 % at

O

STOD1812

DFN10L (3x3 mm)

Description

STOD1812 is a step-up converter designed to
power passive matrix OLED (PMOLED) displays,
providing the pre-charge and biasing voltage of
the column matrix driver. STOD1812 uses a
pulsed frequency modulation (PFM) control mode
technique. The high switching frequency makes it
possible to reduce the value and size of the
external components. This device is particularly
suitable for battery-operated applications, where
overall system efficiency is the major concern.

Synchronous rectification has been integrated in
the device in order to eliminate the external
Schottky diode. An internal compensation net is
also integrated, enabling the STOD1812 to
provide excellent load transient performance in
addition to good load regulation.

The output voltage is set using two external
resistors. Over-temperature protection and under­voltage lockout (UVLO) functions are integrated in
the device. An additional switch implements a true
load disconnection feature which stops the
currrent flowing from the input when the device is
in shutdown mode. The EN pin turns off the
device, reducing the quiescent current to 0.1 µA.

Table 1. Device summary

Order code Package Packaging

STOD1812PUR DFN10L (3x3 mm) 3000 parts per reel

March 2008 Rev 1 1/19

www.st.com

19

Contents STOD1812

Contents

1 Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2 Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

3 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

4 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

5 Functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

5.1 Boost controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

5.2 Enable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

5.3 Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

5.4 Under voltage lockout (UVLO) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

6 Typical application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

7 Demonstration board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

8 Typical application performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

9 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

10 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

2/19

STOD1812 Diagram

1 Diagram

Figure 1. Internal block diagram

Figure 2. Schematic diagram

3/19

Pin configuration STOD1812

2 Pin configuration

Figure 3. Pin connections (top view)

Table 2. Pin description

Pin n° Symbol Description

1 OUT Output voltage

2 OUT Output voltage

3 GND Ground

4 FB Feedback

5EN

6V

7L

8L

I

X

X

DC supply voltage enable control pin. ON =V
shutdown mode.

Input supply voltage.

Switching node

Switching node

9 PGND Power ground

10 PGND Power ground

Exp Pad Exposed Pad. It must be connected to power ground

. When pulled low put the device in

I

4/19

STOD1812 Maximum ratings

3 Maximum ratings

Table 3. Absolute maximum ratings

Symbol Parameter Value Unit

V

I

DC supply voltage -0.3 to 6 V

EN Enable pin -0.3 to 6 V

FB Feedback pin -0.3 to 6 V

Switching node -0.3 to 20 V

Switching current Internally limited A

Converter output voltage -0.3 to 20 V

Power dissipation Internally limited mW

Storage temperature range -65 to 150 °C

Operating temperature range -40 to 125 °C

V

T

L

I

LX

OUT

P

STG

T

X

D

J

Table 4. Thermal data

Symbol Parameter Value Unit

R

thJA

Thermal resistance junction-ambient (tested on 2 layers board) 30.9 °C/W

Table 5. ESD data

Symbol Parameter Value Unit

ESD Human Body Model 2 kV

5/19

Electrical characteristics STOD1812

4 Electrical characteristics

Table 6. Electrical characteristics

(T

= -40 °C to 125 °C, VI = 3.6 V, CI = CO = 4.7 µF, L = 2.2 µH, IO = 80 mA, V

J

V

= 18 V, R1=270 kΩ, R2 = 20 kΩ unless otherwise specified).

O

Symbol Parameter Test conditions Min. Typ. Max. Unit

Supply section

EN

= VI,

V

I

O

UVLO_H

UVLO_L

Supply input voltage IO=0 to 120mA 2.5 5.5 V

I

Load current VI=2.5V to 5.5V 120 mA

Under voltage lockout
HIGH

Under voltage lockout
LOW

2.1 2.2 V

=120mA 1.3 mA

I

O

2.3 2.4 V

No Load, Switching 0.3 mA

I

Q

V

EN

V

EN

I

EN

Quiescent current

VFB=VI - No Load, No Switching 35 50 µA

=GND 100 300 nA

V

EN

H Enable high threshold VI=2.5V to 5.5V 1.2 V

L Enable low threshold VI=2.5V to 5.5V 0.4 V

Enable input current VEN=Vi 500 nA

Dynamic performance

T

ON MAXTON

T

SS

D

MAX

ν Efficiency

max time 0.5 µs

Soft-start time From enable to output regulation 0.6 ms

Maximum duty cycle 95 %

I

=5 to 30mA 75 %

O

=30 to 120mA 85 %

I

O

Step-up converter section

ΔV

ΔV

6/19

V

I

V

O_MAX

ΔV

O_SLO

ΔV

O_LOT

FB1

FB

O_SLI

O_LIT

Feedback voltage VI=2.5V to 5.5V 1.18 1.21 1.24 V

Feedback leakage
current

=2.5V to 5.5V 30 100 nA

V

I

Output voltage range VI=2.5V to 5.5V; IO=0 to 120mA 18 V

Static line regulation VI=2.5V to 5.5V, IO1=120mA, 0.6 %/V

Static load regulation IO=0 to 120mA, VI=3.6V; 0.0016 %/mA

Line transient
regulation

Load transient
regulation

VI=2.5V to 3.0V, IO1=120mA,

=50µs TA=25°C

T

R=TF

IO=5 to 120mA and IO=120 to 5mA,
TR=TF=10µs TA=25°C, peak to peak

80 mV

250 mV