Datasheet STOD13AS 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 250 mA output current

■ 4.6 V fixed positive output voltage

■ Programmable negative voltage by S

WIRE

from

-2.4 V to -6.4 V at 100 mV steps

■ Typical efficiency: 85%

■ Pulse skipping mode in light load condition

■ 1.5 MHz PWM mode control switching

frequency

■ TDMA noise high immunity

■ 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 in

portable devices

■ Cellular phones

■ Camcorders and digital still cameras

Table 1. Device summary

STOD13AS

250 mA dual DC-DC converter

for powering AMOLED displays

DFN12L (3 x 3 mm)

■ Multimedia players

Description

The STOD13AS is a dual DC-DC converter 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
low 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 single-wire protocol. Soft-start
with controlled inrush current limit, thermal
shutdown, and short-circuit protection are
integrated functions of the device.

Order code Positive voltage Negative voltage Package Packaging

STOD13ASTPUR 4.6V -2.4V to -6.4V DFN12L (3 x 3mm) 3000 parts per reel

January 2012 Doc ID 022733 Rev 1 1/25

www.st.com

25

Contents STOD13AS

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

6.3 Enable, S

and FD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

WIRE

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

2/25 Doc ID 022733 Rev 1

STOD13AS Contents

8.1.9 Short-circuit protection during soft-start (SSD) . . . . . . . . . . . . . . . . . . . 18

8.1.10 Overload protection (OLP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

8.1.11 Short-circuit protection (SCP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

8.1.12 Fast discharge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

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

10 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Doc ID 022733 Rev 1 3/25

Schematic STOD13AS

1 Schematic

Figure 1. Application schematic

VBAT

LX1

CIN

S-WIRE

VINP

VINA

S-WIRE

LX1

VMID

STOD13AS

EN

FD

CREF

Table 2. Typical external components

Comp. Manufacturer Part number Value Size Ratings

EN

FD

VREF

PGND

AGND

VO2

LX2

LX2

CMID

CO2

AM10459v1

(1)

L

1

(2)

L

2

C

IN

C

MID

C

O2

C

REF

1. A 250 mA load can be provided with inductor saturation current as a minimum of 0.9 A.

2. At -6.4 V, a 250 mA load can be provided with inductor saturation current as a minimum of 1.5 A. See

CoilCraft

Murata

CoilCraft

Murata

Murata

Taiyo YudeN

Murata

Taiyo YudeN

Murata

Taiyo YudeN

Murata

Taiyo YudeN

LPS4012-472ML

LQH3NPN4R7MM0

LPS4012-472ML

LQH3NPN4R7MM0

GRM219R61A106KE44

LMK212BJ106KD-T

GRM219R61A106KE44

LMK212BJ106KD-T

GRM219R61A106KE44

LMK212BJ106KD-T

GRM185R60J105KE26

JMK107BJ105KK-T

4.7µH

4.7µH

2 x 10µF 0805

10µF

2 x 10µF

1µF

4.0 x 4.0 x 1.2

3.0 x 3.0 x 1.5

4.0 x 4.0 x 1.2

3.0 x 3.0 x 1.5

0805
0805

0805
0805

0603
0603

±20%, I = 1.7A, R = 0.175Ω
±20%, I = 1.25A, R = 0.13Ω

±20%, I = 1.7A, R = 0.175Ω

±20%, I = 1.25A, R = 0.13Ω

±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

Section 7.1.1

.

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 STOD13AS.

4/25 Doc ID 022733 Rev 1

STOD13AS Schematic

UVLO

LOGIC CONTROL

OTP

S-WIRE

RING

KILLER

VREF

OSC

STEP-UP

CONTROL

FAST

DISCHARGE

DMD

INVERTING

CONTROL

FAST

DISCHARGE

DMD

s
s

s

s

V

INA

EN

S

WIRE

V

REF

AGND

PGND

#

#

VREF

S-WIRE
control

N1

s

V

INP

V

MID

V

O2

L

X1

L

X2

P1A

P1B

P2

N2

FD

SSD
SCP
OLP

VO2

LX

CURRENT

SENSE

VINP

Figure 2. Block schematic

AM10458v1

Doc ID 022733 Rev 1 5/25

Pin configuration STOD13AS

2 Pin configuration

Figure 3. Pin configuration (top view)

Table 3. Pin description

Pin name Pin n° Description

Lx

1

1 Boost converter switching node

PGND 2 Power ground pin

V

MID

FD 4

3 Boost converter output voltage

Fast discharge control pin. When pulled LOW, the fast discharge after
shutdown is active. When pulled HIGH, the fast discharge is OFF

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

V

S

REF

WIRE

6

7 Negative voltage setting pin

EN 8

V

O2

Lx

2

V

IN A

V

12 Power input supply voltage

IN P

9 Inverting converter output voltage

10 Inverting converter switching node

11 Analogic input supply voltage

Exposed

pad

Voltage reference output. 1 µF bypass capacitor must be connected
between this pin and AGND

Enable control pin. High = converter on; Low = converter in shutdown
mode

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

6/25 Doc ID 022733 Rev 1

STOD13AS Maximum ratings

3 Maximum ratings

Table 4. Absolute maximum ratings

Symbol Parameter Value Unit

, V

V

INA

EN, S

WIRE

FD Logic input pin -0.3 to V

IL

X2

L

X2

V

O2

V

MID

L

X1

IL

X1

V

REF

P

D

T

STG

T

J

DC supply voltage -0.3 to 6 V

INP

Logic input pins -0.3 to 4.6 V

+0.3 V

INA

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

Human body model protection ±2 kV

ESD

Machine body model protection 200 V

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

Functional operation under these condition is not implied.

The Lx1 and Lx2 have high slew rate and they can be over the absolute maximum rating
during operation due to the parasitic inductance in the PCB and scope probe. An absolute
maximum rating of Lx1 and Lx2 is related to voltage supplied by an external source so the
internally generated Lx1 and Lx2 voltage during normal operation doesn't damage the
chipset.

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 022733 Rev 1 7/25

Electrical characteristics STOD13AS

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

= 4.6 V, V

MID

MID

= 10 µF,

= -4.9 V unless

O2

otherwise specified.

Table 6. Electrical characteristics

Symbol Parameter Test conditions Min. Typ. Max. Unit

General section

V

INA, VINP

UVLO_H Under voltage lockout HIGH V

UVLO_L Under voltage lockout LOW V

I_

I

Q_SH

V

EN

V

EN

I

EN

V

FD

V

FD

I

FD

fs Switching frequency PWM mode 1.35 1.5 1.65 MHz

D1

D2

V

REF

I

REF

Supply input voltage 2.5 3.7 4.5 V

rising 2.22 2.25 V

INA

falling 1.9 2.18 V

INA

VI

Input current No load condition 1.7 2.1 mA

= VSW = GND

V

Shutdown current

H Enable high threshold

EN

T

= -40°C to +85°C

J

=2.5V to 4.5V,

V

INA

= -40°C to +85°C

T

J

1.2 V

L Enable low threshold 0.4

Enable input current

H Fast discharge high threshold

V

EN=VINA

= -40°C to +85°C

T

J

V

INA

= -40°C to +85°C

T

J

=4.5V;

=2.5V to 4.5V,

1.2 V

L Fast discharge low threshold 0.4

=4.5V;

=10 to 30mA,

=4.6V, VO2=-4.9V

=30 to 150mA,

=4.6V, VO2=-4.9V

=150 to 250mA,

=4.6V, VO2=-4.9V

78

85

82

=10µA 1.208 1.220 1.232 V

100 µA

MAX

MAX

V

Fast discharge input current

FD=VINA

= -40°C to +85°C

T

J

Step-up maximum duty cycle No load 87 %

Inverting maximum duty cycle No load 87 %

I

MID,O2

V

MID

I

Total system efficiency

Reference voltage I

Reference current capability

MID,O2

V

MID

I

MID,O2

V

MID

REF

@ 98.5% of no load
reference voltage

1µA

1µA

50 µA

%

Step-up converter section

Positive output voltage 4.6 V

V

V

MID

Positive output voltage total
variation

INA=VINP

I

MID

load T

=2.9V to 4.5V;

=5mA to 250mA, IO2 no

= -40°C to +85°C

J

8/25 Doc ID 022733 Rev 1

-0.8 0.8 %

STOD13AS Electrical characteristics

Table 6. Electrical characteristics (continued)

Symbol Parameter Test conditions Min. Typ. Max. Unit

=3.4V to 2.9V,

V

ΔV

ΔV

MID LT

MID T

Line transient

Load transient response

Undershoot/overshoot

TDMA Noise

I

MID MAX

I-L

1MAX

Static variation between low
and high V

IN

Maximum output current V

Step-up inductor peak current

Step-up converter section

level

INA,P

=100mA; TR=TF=10µs

I

MID

I

=3 to 30mA and I

MID

to 3mA, T

=10 to 100mA and

I

MID

I

=100 to 10mA,

MID

=150µs

T

R=TF

R=TF

=150µs

MID

=30

-10 mV

±20 mV

±25 mV

±20

I

=10 to 50mA; IO2 no load

MID

(1)

=2.9V to 4.5V 250 mA

INA,P

10% below nominal

V

MID

value

1.08 1.32 A

4

mV

P-channel static drain-source

P1

R

R

DSON

DSON

ON resistance

N-channel static drain-source

N1

ON resistance

Inverting converter section

Negative output voltage range

V

O2

Negative output voltage -4.9 V

Negative output voltage total
variation

ΔV

ΔV

O2 LT

O2 T

Line transient

Load transient response

Undershoot/overshoot

TDMA Noise

I

O2 MAX

I-L

2MAX

Static variation between low
and high V

IN

Maximum output current V

Inverting peak current

level

V

INA=VINP

I

SW-P1

V

INA=VINP

I

SW-N1

=3.7V,

=100mA

=3.7V,

=100mA

1.0 2.0 Ω

0.4 1.0 Ω

41 different values set by
S

pin

WIRE

Section 6.1.2

(see

V

INA=VINP

I

O2

load T

V

INA,P

I

O2

I

O2

3mA, T

I

O2

I

O2

T

R=TF

=2.9V to 4.5V;

=5mA to 250mA, I

= -40°C to +85°C

J

=3.4V to 2.9V,

=100mA, TR=TF=10µs

=3 to 30mA and IO2=30 to

R=TF

=10 to 100mA and
=100 to 10mA,

=150µs

)

=150µs

MID

no

-6.4 -2.4 V

-1.7 1.7 %

+10 mV

±20 mV

±25 mV

±20

IO2=10 to 50mA; I

(1)

=2.9V to 4.5V -250 mA

INA,P

below 10% of nominal

V

O2

value

MID

no load

5

-1.6 -1.3 A

mV

R

DSON

P-channel static drain-source

P2

ON resistance

V

INA=VINP

I

SW-P2

=3.7V,

=100mA

0.42 0.8 Ω

Doc ID 022733 Rev 1 9/25

Electrical characteristics STOD13AS

Table 6. Electrical characteristics (continued)

Symbol Parameter Test conditions Min. Typ. Max. Unit

R

DSON

N-channel static drain-source

N2

ON resistance

V

INA=VINP

I

SW-N2

=3.7V,

=100mA

0.43 0.8 Ω

Thermal shutdown

OTP Overtemperature protection 140 °C

OTP

HYST

Overtemperature protection
hysteresis

15 °C

Discharge resistor

R

DIS

Resistor value No load, EN=SW=FD=Low 400 Ω

No load, EN=SW=FD=Low,

T

DIS

Discharge time

V

MID-VO2

at 10% of nominal

10 ms

value

1. V

= 4.2 to 3.7 V, 3.7 to 3.2 V, 3.4 to 2.9 V, f = 200 Hz; t

INA,P

= 3.65 ms; t

ON

= 1.25 ms; TR = TF = 10 µs, pulse signal.

OFF

10/25 Doc ID 022733 Rev 1

STOD13AS Typical performance characteristics

5 Typical performance characteristics

V

= V

INA

the tests below.

Figure 4. Maximum power output vs. input

4.50

4.25

4.00

3.75

3.50

3.25

3.00

2.75

2.50

P_OUT [W]

2.25

2.00

1.75

1.50

1.25

1.00

2.5 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5

voltage

= 3.7 V, VO2 = -4.9 V, TJ = 25 °C; See

INP

Figure 5. Efficiency vs. output current

Po1,2 MAX

V_IN [V]

Efficiency [%]

Ta bl e 1

90.0

87.5

85.0

82.5

80.0

77.5

75.0

72.5

70.0

67.5

65.0
52035 50 65 95 110 125 140 155 170 185200215230245260

for external components used in

3.4 V

3.7 V

3.8 V

4 V

4.2 V

4.5 V

I

[mA]

LOAD

Figure 6. Total system efficiency vs. I

90.0

87.5

85.0

82.5

80.0

77.5

75.0

Efficiency [% ]

72.5

70.0

67.5

65.0
5 25 45 65 85 105 125 145 165 185 205 225 245

I

LOAD

Coilcra
LPS4012 at 3.7 V

muRat a
LQH3NPN at 3.7 V

[mA]

LOAD

Figure 7. Soft-start and inrush current

Doc ID 022733 Rev 1 11/25

Typical performance characteristics STOD13AS

Figure 8. Fast discharge no load,

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

EN=SW=FD=Low

Figure 9. Switching and output waveforms

V

= V

INA

= 2.9 V, I

INP

= 250 mA, TJ = 85 °C

MID,O2

V

= V

INA

INP

= 2.9 V, I

= 100 mA, TJ = 25 °C

MID

V

= V

INA

INP

12/25 Doc ID 022733 Rev 1

= 2.9 V, I

= 100 mA, TJ = 25 °C

MID

STOD13AS 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 STOD13AS 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

● Simplify 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 (STOD13AS) 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 022733 Rev 1 13/25

in combination with the Enable pin.

WIRE

Detailed description STOD13AS

6.2 Negative output voltage levels

Table 7. Negative output voltage levels

Pulse V

O2

Pulse V

O2

Pulse V

O2

Pulse V

1 -6.411-5.421-4.431 -3.4

2 -6.312-5.322-4.332 -3.3

3 -6.213-5.223-4.233 -3.2

4 -6.114-5.124-4.134 -3.1

5 -6.015-5.025-4.035 -3.0

6-5.916

(1)

-4.9 26 -3.9 36 -2.9

7 -5.817-4.827-3.837 -2.8

8 -5.718-4.728-3.738 -2.7

9 -5.619-4.629-3.639 -2.6

10 -5.5 20 -4.5 30 -3.5 40 -2.5

41 -2.4

1. Default value.

6.3 Enable, S

WIRE

and FD

O2

Table 8. Enable and S

operation table

WIRE

Enable S

Low Low Device off

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

Table 9. Fast discharge operation table

FD pin Action

Low Fast discharge active after IC shutdown

High No fast discharge function

WIRE

WIRE

(1)

Action

WIRE

function.

14/25 Doc ID 022733 Rev 1

STOD13AS 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 of the STOD13AS;

IN

f

: switching frequency. Use the minimum value of 1.35 MHz for the worst case;

s

η1: efficiency of step-up converter. Typical value is 0.70;

η2: efficiency of inverting converter. Typical value is 0.60.

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 -6.4 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 022733 Rev 1 15/25

and 2 x 10 µF, 10 V

MID

Application information STOD13AS

7.2 Recommended PCB layout

The STOD13AS is a 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 12. Top layer and silk-screen (top view, not to scale)

Figure 13. Bottom layer and silk-screen (top view, not to scale)

16/25 Doc ID 022733 Rev 1

STOD13AS Detailed description

8 Detailed description

8.1 General description

The STOD13AS 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 STOD13AS 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 performance and low noise operation.

The STOD13AS 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 STOD13AS operate in three different modes:
pulse skipping (PSM), 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 STOD13AS 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 (VO2) for the
inverting converter.

8.1.3 Discontinuous conduction mode

When the load increases above a few mA, the STOD13AS 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

At medium/high output loads, the STOD13AS enters full CCM at constant switching
frequency mode for each of the two DC-DC converters.

Doc ID 022733 Rev 1 17/25

Detailed description STOD13AS

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.

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 start-up 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 13 ms after the
EN pin is asserted high.

8.1.7 Undervoltage lockout

The undervoltage lockout function avoids improper operation of the STOD13AS 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 50 mV 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 during soft-start (SSD)

INP

, V

INA

and EN, the

During device soft-start on the positive output, an internal comparator checks if the panel is
damaged. In this case, soft-start is stopped and the device is parked in power-off. To reset
the normal functionality (assuming that the anomalous load condition is removed), it is
necessary to restart the converter through an enable transient.

If the panel is not damaged it is possible to proceed with the soft-start of the negative output
and both reach their final value, therefore ensuring normal output voltages and functionality.

8.1.10 Overload protection (OLP)

The output current is internally limited. An overload condition, as a short-circuit between the
two outputs or between each output and GND, produces the device power-off. To reset the

18/25 Doc ID 022733 Rev 1

STOD13AS Detailed description

normal functionality (assuming that the short condition is removed), it is necessary to restart
the converter through an enable transient.

8.1.11 Short-circuit protection (SCP)

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

. Overshoots are limited, decreasing the inductor current. After that, the output

OUT

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 short­circuit protection is active.

8.1.12 Fast discharge

When ENABLE turns from high to low level, the device goes into shutdown mode LX1 and
LX2 stop switching. If the FD pin is low, a resistor of about 400 Ω is connected between
V

and VO2 to discharge quickly C

MID

differential output voltage (V

MID-VO2

voltages are discharged to 0 V, the switches turn off and the outputs are high impedance.
When the FD pin is high, the fast discharge after shutdown is off.

and CO2 capacitors, lowering in about 10 ms the

MID

) below 10% of nominal value. When the output

Doc ID 022733 Rev 1 19/25

Package mechanical data STOD13AS

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

20/25 Doc ID 022733 Rev 1

STOD13AS Package mechanical data

Table 10. 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 14. DFN12L (3 x 3) drawing

8085116-A

Doc ID 022733 Rev 1 21/25

Package mechanical data STOD13AS

Tape & reel QFNxx/DFNxx (3x3) mechanical data

mm. inch

DIM.

MIN. TYP MAX. MIN. TYP. MAX.

A 330 12.992

C 12.8 13.2 0.504 0.519

D 20.2 0.795

N 99 101 3.898 3.976

T 14.4 0.567

Ao 3.3 0.130

Bo 3.3 0.130

Ko 1.1 0.043

Po 4 0.157

P 8 0.315

22/25 Doc ID 022733 Rev 1

STOD13AS Package mechanical data

Figure 15. DFN12L (3 x 3 mm) footprint recommended data

Doc ID 022733 Rev 1 23/25

Revision history STOD13AS

10 Revision history

Table 11. Document revision history

Date Revision Changes

27-Jan-2012 1 Initial release.

24/25 Doc ID 022733 Rev 1

STOD13AS

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