Datasheet STOD03AS Datasheet (ST)

Features

■ Step-up and inverter converters

■ Operating input voltage range from 2.5 V to

4.5 V

■ Synchronous rectification for both DC-DC

converters

■ Minimum 200 mA output current

■ 4.6 V fixed positive output voltage

■ Programmable negative voltage by S

WIRE

from

-2.4 V to -5.4 V at 100 mV steps

■ Typical efficiency: 85%

■ Pulse skipping mode in light load condition

■ 1.5 MHz PWM mode control switching

frequency

■ Enable pin for shutdown mode

■ Low quiescent current in shutdown mode

■ Soft-start with inrush current protection

■ Overtemperature protection

■ Temperature range: -40 °C to 85 °C

■ True-shutdown mode

■ Fast discharge outputs of the circuits after

shutdown

■ Short-circuit protection

■ Package DFN12L (3 x 3 mm) 0.6 mm height

Applications

■ Active matrix AMOLED power supply

■ Cellular phones

■ Camcorders and digital still cameras

■ Multimedia players

STOD03AS

Dual DC-DC converter

for powering AMOLED displays

DFN12L (3 x 3 mm)

Description

The STOD03AS is a dual DC-DC converter with
short-circuit protection for AMOLED display
panels. It integrates a step-up and an inverting
DC-DC converter making it particularly suitable
for battery operated products, in which the major
concern is overall system efficiency. It works in
pulse skipping mode during light load conditions
and PWM-MODE at 1.5 MHz frequency for
medium/high load conditions. The high frequency
allows the value and size of external components
to be reduced. The Enable pin allows the device
to be turned off, therefore reducing the current
consumption to less than 1 µA. The negative
output voltage can be programmed by an MCU
through a dedicated pin which implements single­wire protocol. Soft-start with controlled inrush
current limit and thermal shutdown are integrated
functions of the device.

Table 1. Device summary

Order code Positive voltage Negative voltage Package Packaging

STOD03ASTPUR 4.6V -2.4V to -5.4V DFN12L (3 x 3 mm) 3000 parts per reel

December 2011 Doc ID 022614 Rev 1 1/24

www.st.com

24

Contents STOD03AS

Contents

1 Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2 Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

3 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

4 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

5 Typical performance characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

6 Detailed description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

6.1 S

6.1.1 S

6.1.2

6.1.3

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

WIRE

features and benefits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

WIRE

S

S

protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

WIRE

basic operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

WIRE

6.2 Negative output voltage levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

7 Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

7.1 External passive components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

7.1.1 Inductor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

7.1.2 Input and output capacitor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

7.2 Recommended PCB layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

8 Detailed description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

8.1 General description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

8.1.1 Multiple operation modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

8.1.2 Pulse skipping operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

8.1.3 Discontinuous conduction mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

8.1.4 Continuous conduction mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

8.1.5 Enable pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

8.1.6 Soft-start and inrush current limiting . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

8.1.7 Undervoltage lockout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

8.1.8 Overtemperature protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

8.1.9 Short-circuit protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

2/24 Doc ID 022614 Rev 1

STOD03AS Contents

8.1.10 Fast discharge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

9 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

10 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Doc ID 022614 Rev 1 3/24

Schematic STOD03AS

1 Schematic

Figure 1. Application schematic

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Table 2. Typical external components

Comp. Manufacturer Part number Value Size Ratings

CoilCraft

Murata

(1)

L

1

SEMCO

ABCO
ABCO

CoilCraft

Murata

(2)

L

2

TOKO
ABCO

TDK

C

IN

C

MID

C

O2

C

REF

1. A 200 mA load can be provided with inductor saturation current as a minimum of 0.5 A.

2. At -5.4 V, a 200 mA load can be provided with inductor saturation current as a minimum of 1 A. See Section 7.1.1.

Murata

Taiyo Yuden

Murata

Taiyo Yuden

Murata

Taiyo Yuden

Murata

Taiyo Yuden

LPS4012-472ML

LQH3NPN4R7MJ0

CIG22B4R7MNE

LPF2810T-4R7M
LPF2807T-4R7M

LPS4012-472ML

LQH3NPN4R7MJ0

DFE252012C1239AS-H4R7N

LPF3510T-4R7M

VLF4014AT-4R7M1R1

GRM219R61A106KE44

LMK212BJ106KD-T

GRM219R61A106KE44

LMK212BJ106KD-T

GRM219R61A106KE44

LMK212BJ106KD-T

GRM185R60J105KE26

JMK107BJ105KK-T

4.7µH

4.7µH

2 x

10µF

10µF

2 x

10µF

1µF

4.0 x 4.0 x 1.2

3.0 x 3.0 x 1.1

2.5 x 2.0 x 1.0

2.8 x 2.8 x 1.0

2.8 x 2.8 x 0.7

4.0 x 4.0 x 1.2

3.0 x 3.0 x 1.1

2.5 x 2.0 x 1.2

3.5 x 3.5 x 1.0

3.7 x 3.5 x 1.4

0805
0805

0805
0805

0805
0805

0603
0603

±20%, I = 1.7 A, R = 0.175Ω
±20%, I = 1.1 A, R = 0.156Ω
±20%, I = 1.1 A, R = 0.300Ω
±20%, I = 0.85 A, R = 0.33Ω
±20%, I = 0.70 A, R = 0.44Ω

±20%, I = 1.7 A, R = 0.175Ω
±20%, I = 1.1 A, R = 0.156Ω
±30%, I = 1.2 A, R = 0.252Ω
±20%, I = 0.83 A, R = 0.25Ω
±20%, I = 1.1 A, R = 0.140Ω

±10%, X5R, 10V
±10%, X5R, 10V

±10%, X5R, 10V
±10%, X5R, 10V

±10%, X5R, 10V
±10%, X5R, 10V

±10%, X5R, 6.3V
±10%, X5R, 6.3V

Note: All the above components refer to the typical application performance characteristics.

Operation of the device is not limited to the choice of these external components. Inductor
values ranging from 3.3 µH to 6.8 µH can be used together with the STOD03AS.

4/24 Doc ID 022614 Rev 1

STOD03AS Schematic

Figure 2. Block schematic

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Doc ID 022614 Rev 1 5/24

Pin configuration STOD03AS

2 Pin configuration

Figure 3. Pin configuration (top view)

Table 3. Pin description

Pin name Pin n° Description

Lx

1

1 Switching node of the step-up converter

PGND 2 Power ground pin

V

MID

3 Step-up converter output voltage (4.6V)

NC 4 Not internally connected

AGND 5 Signal ground pin. This pin must be connected to the power ground pin

Voltage reference output. 1µF bypass capacitor must be connected

V

REF

S

WIRE

EN 8

V

O2

Lx

2

V

IN A

V

iN P

6

between this pin and AGND

7 Negative voltage setting pin

Enable control pin. ON = V

. When pulled low it puts the device in

INA

shutdown mode

9 Inverting converter output voltage (Default - 4.9V)

10 Switching node of the inverting converter

11 Analogic input supply voltage

12 Power input supply voltage

Exposed

pad

Internally connected to AGND. Exposed pad must be connected to AGND
and PGND in the PCB layout in order to guarantee proper operation of the
device

6/24 Doc ID 022614 Rev 1

STOD03AS Maximum ratings

3 Maximum ratings

Table 4. Absolute maximum ratings

Symbol Parameter Value Unit

V

INA

EN, S

IL

L

V

V

L

IL

V

P

T

, V

X2

X2

O2

MID

X1

X1

REF

D

STG

T

J

WIRE

DC supply voltage -0.3 to 6 V

INP

Logic input pins -0.3 to 4.6 V

Inverting converter switching current Internally limited A

Inverting converter switching node voltage - 10 to V

+ 0.3 V

INP

Inverting converter output voltage - 10 to AGND + 0.3 V

Step-up converter and LDO output voltage -0.3 to 6 V

Step-up converter switching node voltage -0.3 to V

+ 0.3 V

MID

Step-up converter switching current Internally limited A

Reference voltage -0.3 to 3 V

Power dissipation Internally limited mW

Storage temperature range -65 to 150 °C

Maximum junction temperature 150 °C

ESD ESD protection HBM 2 kV

Note: Absolute maximum ratings are those values beyond which damage to the device may occur.

Functional operation under these conditions is not implied.

Table 5. Thermal data

Symbol Parameter Value Unit

R

thJA

R

thJC

1. The package is mounted on a 4-layer (2S2P) JEDEC board as per JESD51-7.

Thermal resistance junction-ambient 33 °C/W

Thermal resistance junction-case (FR-4 PCB)

(1)

2.12 °C/W

Doc ID 022614 Rev 1 7/24

Electrical characteristics STOD03AS

4 Electrical characteristics

TJ = 25 °C, V
C

= 2 x 10 µF, C

O2

INA

= V

= 3.7 V, I

INP

= 1 µF, L1 = L2 = 4.7 µH, V

REF

MID,O2

= 30 mA, C

= 2 x 10 µF, C

IN

= 2 V, V

EN

= 10 µF,

MID

= 4.6 V, VO2= -4.9 V unless

MID

otherwise specified.

Table 6. Electrical characteristics

Symbol Parameter Test conditions Min. Typ. Max. Unit

General section

V

INA, VINP

UVLO_H Undervoltage lockout HIGH V

UVLO_L Undervoltage lockout LOW V

I_V

I

Q_SH

V

EN

V

EN

I

EN

f

D1

D2

η Total system efficiency

V

REF

I

REF

Supply input voltage 2.3 3.7 4.5 V

rising 2.22 2.25 V

INA

falling 1.9 2.18 V

INA

Input current No load condition 1.7 2.1 mA

I

=GND

V

Shutdown current

H Enable high threshold

L Enable low threshold 0.4

Enable input current

S

MAX

MAX

Switching frequency PWM mode 1.2 1.5 1.7 MHz

Step-up maximum duty cycle No load 87 %

Inverting maximum duty cycle No load 87 %

Voltage reference I

Voltage reference current
capability

EN

TJ=-40°C to +85°C

V

=2.5V to 4.5V,

INA

1.2

TJ=-40°C to +85°C

V

EN=VINA

=-40°C to +85°C

T

J

I

MID,O2

V

MID

I

MID,O2

V

MID

REF

At 98.5% of no load
reference voltage

=4.5V

=10 to 30mA,

=4.6V, VO2=-4.9V

=30 to 150mA,

=4.6V, VO2=-4.9V

80 %

85 %

=10µA 1.216 1.228 1.240 V

100 µA

1µA

1µA

V

Step-up converter section

Positive voltage total variation

V

INA=VINP

I

MID

=2.5V to 4.5V;

=5mA to 150mA, IO2 no

load, TJ=25°C

V

MID

Temperature accuracy

V

INA=VINP

I

O2

=3.7V; I

no load; TJ=-40°C to

MID

+85°C

=3.5V to 3.0V,

V

ΔV

MID LT

Line transient

INA,P

=100mA; TR=TF=50µs

I

MID

8/24 Doc ID 022614 Rev 1

4.55 4.6 4.65 V

=5mA;

±0.5 %

-12 mV

STOD03AS Electrical characteristics

Table 6. Electrical characteristics (continued)

Symbol Parameter Test conditions Min. Typ. Max. Unit

I

ΔV

MIDT

V

MID-PP

I

MID MAX

I-L

1MAX

R

DSON

Load transient regulation

TDMA noise line transient
regulation

Max. step-up load current V

Step-up inductor peak current

P-channel static drain-source

P1

ON resistance

=3 to 30mA and I

MID

to 3mA, T

=10 to 100mA and

I

MID

I

=100 to 10mA,

MID

=30µs

T

R=TF

=5 to 100mA; V

I

MID

R=TF

=30µs

=2.9V to 3.4V; F=200Hz;

=50µs; IO2 no load

T

R=TF

=2.9V to 4.5V 200 mA

INA,P

10% below of nominal

V

MID

value

V

=3.7V, ISW=100mA 1.0 2.0 Ω

INA,P

MID

INA,P

=30

±20 mV

±25 mV

±20 mV

0.9 1.1 A

R

DSON

N-channel static drain-source

N1

ON resistance

Inverting converter section

Output negative voltage range

V

O2

Output negative voltage total
variation on default value

Temperature accuracy

ΔV

O2 LT

Line transient

Load transient regulation

ΔV

O2T

Load transient regulation

V

O2-PP

I

O2

TDMA noise line transient
regulation

Maximum inverting output
current

V

=3.7V, ISW=100mA 0.4 1.0 Ω

INA,P

31 different values set by the
S

WIRE

pin

-5.4 -2.4 V

(see Section 6.1.2)

V

INA=VINP

IO2=5mA to 150mA, I

=2.5V to 4.5V;

MID

no

-4.97 -4.9 -4.83 V

load, TJ=25°C

V

INA=VINP

I

MID

=3.7V; IO2=5mA,

no load,

±0.5 %

TJ=-40°C to +85°C

V

=3.5V to 3.0V,

INA,P

IO2=100mA, TR=TF=50µs

=3 to 30mA and IO2=30 to

I

O2

3mA, T

=10 to 100mA and

I

O2

=100 to 10mA,

I

O2

T

R=TF

=5 to 100mA; V

I

O2

R=TF

=100µs

=100µs

INA,P

=2.9V to 3.4V; F=200Hz;

=50µs; I

T

R=TF

V

=2.9V to 4.5V -200 mA

INA,P

MID

no load

+12 mV

±20 mV

±25 mV

±25 mV

R

R

I-L

2MAX

DSON

DSON

Inverting peak current

P-channel static drain-source

P2

ON resistance

N-channel static drain-source

N2

ON resistance

V

below 10% of nominal

O2

value

=3.7V, ISW=100mA 0.42 Ω

V

INA,P

V

=3.7V, ISW=100mA 0.43 Ω

INA,P

-1.2 -0.9 A

Doc ID 022614 Rev 1 9/24

Electrical characteristics STOD03AS

Table 6. Electrical characteristics (continued)

Symbol Parameter Test conditions Min. Typ. Max. Unit

Thermal shutdown

OTP Overtemperature protection 140 °C

OTP

HYST

Overtemperature protection
hysteresis

Discharge resistor

R

DIS

T

DIS

Resistor value No load 400 Ω

Discharge time

No load, V

MID-VO2

nominal value

at 10% of

15 °C

8ms

10/24 Doc ID 022614 Rev 1

STOD03AS Typical performance characteristics

5 Typical performance characteristics

V

= - 4.9 V; TA = 25 °C; See Ta bl e 1 for external components used in the tests below.

O2

Figure 4. Efficiency vs. input voltage Figure 5. Efficiency vs. output current

Efficiency [%]

90%

88%

86%

84%

82%

80%

78%

76%

74%

72%

70%

68%

66%

2.5 2.7 2.9 3.1 3.33.5 3.7 3.9 4.1 4.3 4.5

Io=50mA

Io=100mA

Io=150mA

Io=200mA

VIN[V]

90%

85%

80%

75%

70%

Efficiency [%]

65%

60%

55%

50%

020406080 100 120 140 160 180200

VIN=2.7V

VIN=3.2V

VIN=3.7V

VIN=4.2V

I

OUT

[mA]

Figure 6. Input current vs. VIN no load Figure 7. Max. power output vs. V

Figure 8. Fast discharge V

= 3.7 V, no load Figure 9. Startup and inrush V

IN

V

EN

MID

TA = 25 °C

500

450

400

350

[mA]

300

OUT

I

250

200

max I

max P

OUT

OUT

at V

O2

150

100

2.5 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5

VIN[V]

load

= -4.9V

IN

IN,

4.0

3.5

3.0

2.5

[W]

2.0

OUT

P

1.5

1.0

0.5

0.0

= 3.7 V, no

V

O2

I

IN

Doc ID 022614 Rev 1 11/24

Typical performance characteristics STOD03AS

INA

= V

= 3.7 V, I

INP

= 100 mA, TA = 25 °C

MID

VEN = V

INA

= V

= 3.7 V, IO2 = 100 mA, TA = 25 °C

INP

Figure 10. Step-up CCM operation Figure 11. Inverting CCM operation

VEN = V

Figure 12. Line transient Figure 13. Output voltage vs. input voltage

I

= 200 mA, V

O

10.00

9.00

V

IN

8.00

7.00

V

MID

[V]

+V

V

6.00

O2

5.00

O1

4.00

-40 °C

25 °C

85 °C

3.00

V

O2

2.00

1.00

0.00

1.6 1.8 2 2.2 2.4 2.6 2.8 3

V

= V

INA

= 2.9 to 3.4 V, I

INP

= 100 mA, TR = TF = 50 µs

MID,O2

O2

V

IN

= - 4.9 V

[V]

12/24 Doc ID 022614 Rev 1

STOD03AS Detailed description

6 Detailed description

6.1 S

● Protocol: to digitally communicate over a single cable with single-wire components

● Single-wire's 3 components:

1. an external MCU

2. wiring and associated connectors

3. the STOD03AS device with a dedicated single-wire pin.

6.1.1 S

● Fully digital signal

● No handshake needed

● Protection against glitches and spikes though an internal low pass filter acting on falling

● Uses a single wire (plus analog ground) to accomplish both communication and power

● Simplified design with an interface protocol that supplies control and signaling over a

6.1.2 S

● Single-wire protocol uses conventional CMOS/TTL logic levels (maximum 0.6 V for

● Both master (MCU) and slave (STOD03AS) are configured to permit bit sequential data

● Data is bit-sequential with a START bit and a STOP bit

● Signal is transferred in real time

● System clock is not required; each single-wire pulse is self-clocked by the oscillator

WIRE

features and benefits

WIRE

edges

control transmission

single-wire connection to set the output voltages.

protocol

WIRE

logic “zero” and a minimum 1.2 V for logic “one”) with operation specified over a supply
voltage range of 2.5 V to 4.5 V

to flow only in one direction at a time; master initiates and controls the device

integrated in the master and is asserted valid within a frequency range of 250 kHz
(maximum).

6.1.3 S

basic operations

WIRE

● The negative output voltage levels are selectable within a wide range (steps of 100 mV)

● The device can be enabled / disabled via S

Doc ID 022614 Rev 1 13/24

in combination with the Enable pin.

WIRE

Detailed description STOD03AS

6.2 Negative output voltage levels

Table 7. Negative output voltage levels

Pulse V

O2

Pulse V

1 -5.411-4.421-3.4

2 -5.312-4.322-3.3

3 -5.213-4.223-3.2

4 -5.114-4.124-3.1

5 -5.015-4.025-3.0

(1)

6

-4.9 16 -3.9 26 -2.9

7 -4.817-3.827-2.8

8 -4.718-3.728-2.7

9 -4.619-3.629-2.6

10 -4.5 20 -3.5 30 -2.5

1. Default output voltage.

Table 8. Enable and S

operation table

WIRE

Enable S

Low Low Device off

(1)

WIRE

O2

Pulse V

31 -2.4

Action

O2

Low High Negative output set by S

High Low Default negative output voltage

High High Default negative output voltage

1. The Enable pin must be set to AGND while using the S

WIRE

WIRE

function.

14/24 Doc ID 022614 Rev 1

STOD03AS Application information

7 Application information

7.1 External passive components

7.1.1 Inductor selection

Magnetic shielded low ESR power inductors must be chosen as the key passive
components for switching converters.

For the step-up converter an inductance between 4.7 µH and 6.8 µH is recommended.
For the inverting stage the suggested inductance ranges from 3.3 µH to 4.7 µH.
It is very important to select the right inductor according to the maximum current the
inductor can handle to avoid saturation. The step-up and the inverting peak current can be
calculated as follows:

Equation 1

IV

×

I

−

=

BOOSTPEAK

OUTMID

VIN1

×η

+

MIN

MID

−×

×××

)VINV(VIN

MINMIDMIN

1LfsV2

Equation 2

x-

x-

)2(

IVOVIN

)2(

MIN

MIN

IVOVIN

=

I

I

-

-

INVERTINGPEAK

INVERTINGPEAK

=

x

x

η

η

2

VIN

2

VIN

where

V

: step-up output voltage, fixed at 4.6 V;

MID

V

: inverting output voltage including sign (minimum value is the absolute maximum

O2

value);

I

: output current for both DC-DC converters;

O

V

: input voltage for the STOD03AS;

IN

f

: switching frequency. Use the minimum value of 1.2 MHz for the worst case;

s

η1: efficiency of step-up converter. Typical value is 0.85;

η2: efficiency of inverting converter. Typical value is 0.75.

The negative output voltage can be set via S

WIRE

current, at the maximum load condition, increases. A proper inductor, with a saturation
current as a minimum of 1 A, is preferred.

7.1.2 Input and output capacitor selection

x

x

2

VOVIN

2

VOVIN

OUTMINMIN

OUTMINMIN

+

+

x

x

MINMIN

MINMIN

xx-

xx-

2)2(2

LfsVINVO

2)2(2

MINMIN

MINMIN

LfsVINVO

at - 5.4 V. Accordingly, the inductor peak

It is recommended to use X5R or X7R low ESR ceramic capacitors as input and output
capacitors in order to filter any disturbance present in the input line and to obtain stable
operation for the two switching converters. A minimum real capacitance value of 6 µF must
be guaranteed for C
variation and DC polarization, a 10 µF, 10 V ±10% capacitor as C
±10% as C

, can be used to achieve the required 6 µF.

O2

and CO2 in all conditions. Considering tolerance, temperature

MID

Doc ID 022614 Rev 1 15/24

and 2 x 10 µF, 10 V

MID

Application information STOD03AS

7.2 Recommended PCB layout

The STOD03AS is high frequency power switching device and therefore requires a proper
PCB layout in order to obtain the necessary stability and optimize line/load regulation and
output voltage ripple.

Analog input (V
at the C

pad only. The input capacitor must be as close as possible to the IC.

IN

) and power input (V

INA

) must be kept separated and connected together

INP

In order to minimize the ground noise, a common ground node for power ground and a
different one for analog ground must be used. In the recommended layout, the AGND node
is placed close to C

ground while the PGND node is centered at CIN ground. They are

REF

connected by a separated layer routing on the bottom through vias.

The exposed pad is connected to AGND through vias.

Figure 14. Top layer and silk-screen (top view, not to scale)

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STOD03AS Application information

Figure 15. Bottom layer and silk-screen (top view, not to scale)

Doc ID 022614 Rev 1 17/24

Detailed description STOD03AS

8 Detailed description

8.1 General description

The STOD03AS is a high efficiency dual DC-DC converter which integrates a step-up and
inverting power stage suitable for supplying AMOLED panels. Thanks to the high level of
integration it needs only 6 external components to operate and it achieves very high
efficiency using a synchronous rectification technique for each of the two DC-DC converters.

The controller uses an average current mode technique in order to obtain good stability and
precise voltage regulation in all possible conditions of input voltage, output voltage, and
output current. In addition, the peak inductor current is monitored in order to avoid saturation
of the coils.

The STOD03AS implements a power saving technique in order to maintain high efficiency at
very light load and it switches to PWM operation as the load increases in order to guarantee
the best dynamic performances and low noise operation.

The STOD03AS avoids battery leakage thanks to the true-shutdown feature and it is self
protected from overtemperature. Undervoltage lockout and soft-start guarantee proper
operation during startup.

8.1.1 Multiple operation modes

Both the step-up and the inverting stage of the STOD03AS operate in three different modes:
pulse skipping (PS), discontinuous conduction mode (DCM) and continuous conduction
mode (CCM). It switches automatically between the three modes according to input voltage,
output current, and output voltage conditions.

8.1.2 Pulse skipping operation

The STOD03AS works in pulse skipping mode when the load current is below some tens of
mA. The load current level at which this way of operation occurs depends on input voltage
only for the step-up converter and on input voltage and negative output voltage (V
inverting converter.

8.1.3 Discontinuous conduction mode

When the load increases above a few mA, the STOD03AS enters DCM operation. In order
to obtain this type of operation the controller must avoid the inductor current going negative.
The discontinuous mode detector (DMD) blocks sense the voltage across the synchronous
rectifiers (P1B for the step-up and N2 for the inverting) and turn off the switches when the
voltage crosses a defined threshold which, in turn, represents a certain current in the
inductor. This current can vary according to the slope of the inductor current which depends
on input voltage, inductance value, and output voltage.

8.1.4 Continuous conduction mode

) for the

O2

At medium/high output loads, the STOD03AS enters full CCM at constant switching
frequency mode for each of the two DC-DC converters.

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STOD03AS Detailed description

8.1.5 Enable pin

The device operates when the EN pin is set high. If the EN pin is set low, the device stops
switching, and all the internal blocks are turned off. In this condition the current drawn from
V

INP/VINA

is below 1 µA in the whole temperature range. In addition, the internal switches
are in an OFF state so the load is electrically disconnected from the input, this avoids
unwanted current leakage from the input to the load.

When the EN is pulled high, the P1B switch is turned on for 100 µs. In normal operation,
during this time, apart of a small drop due to parasitic resistance, V
If, after this 100 µs, V

stays below VIN, the P1B is turned off and stays off until a new

MID

reaches VIN.

MID

pulse is applied to the EN. This mechanism avoids the STOD03AS starting if a short-circuit
is present on V

MID

.

8.1.6 Soft-start and inrush current limiting

After the EN pin is pulled high, or after a suitable voltage is applied to V
device initiates the startup phase.

As a first step, the C

capacitor is charged and the P1B switch implements a current

MID

limiting technique in order to keep the charge current below 400 mA. This avoids the battery
overloading during startup.

After V

reaches the V

MID

voltage level, the P1B switch is fully turned on and the soft-start

INP

procedure for the step-up is started. After around 2 ms the soft-start for the inverting is
started. The positive and negative voltages are under regulation at around 6 ms after the
EN pin is asserted high.

8.1.7 Undervoltage lockout

The undervoltage lockout function avoids improper operation of the STOD03AS when the
input voltage is not high enough. When the input voltage is below the UVLO threshold the
device is in shutdown mode. The hysteresis of 50mV avoids unstable operation when the
input voltage is close to the UVLO threshold.

8.1.8 Overtemperature protection

An internal temperature sensor continuously monitors the IC junction temperature. If the IC
temperature exceeds 140 °C, typical, the device stops operating. As soon as the
temperature falls below 125 °C, typical, normal operation is restored.

8.1.9 Short-circuit protection

INP

, V

INA

and EN, the

When short-circuit occurs, the device is able to detect the voltage difference between VIN
and V

. Overshoots on LX1 are limited, decreasing the inductor current. After that, the

MID

output stages of the device are turned off. This status is maintained, avoiding current flowing
to the load. A new ENABLE transition is needed to restart the device. During startup the
short-circuit protection is active.

8.1.10 Fast discharge

When ENABLE turns from high to low level, the device goes into shutdown mode and LX1
and LX2 stop switching. Then, the discharge switch between V
between V
output voltage. When the output voltages are discharged to 0 V, the switches turn off and the
outputs are high impedance.

and GND turn on and discharge the positive output voltage and negative

O2

and VIN and the switch

MID

Doc ID 022614 Rev 1 19/24

Package mechanical data STOD03AS

9 Package mechanical data

In order to meet environmental requirements, ST offers these devices in different grades of
ECOPACK
specifications, grade definitions and product status are available at:
is an ST trademark.

®

packages, depending on their level of environmental compliance. ECOPACK

www.st.com. ECOPACK

20/24 Doc ID 022614 Rev 1

STOD03AS Package mechanical data

Table 9. DFN12L (3 x 3) mechanical data

mm. inch.

Dim.

Min. Typ. Max. Min. Typ. Typ.

A 0.51 0.55 0.60 0.020 0.022 0.024

A1 0 0.02 0.05 0 0.001 0.002

A3 0.20 0.008

b 0.18 0.25 0.30 0.007 0.010 0.012

D 2.85 3 3.15 0.112 0.118 0.124

D2 1.87 2.02 2.12 0.074 0.080 0.083

E 2.85 3 3.15 0.112 0.118 0.124

E2 1.06 1.21 1.31 0.042 0.048 0.052

e 0.45 0.018

L 0.30 0.40 0.50 0.012 0.016 0.020

Figure 16. DFN12L (3 x 3) drawing

8085116-A

Doc ID 022614 Rev 1 21/24

Package mechanical data STOD03AS

Figure 17. DFN12L (3 x 3 mm) footprint recommended data

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STOD03AS Revision history

10 Revision history

Table 10. Document revision history

Date Revision Changes

20-Dec-2011 1 Initial release.

Doc ID 022614 Rev 1 23/24

STOD03AS

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