Datasheet SS8028G Datasheet (Silicon Standard) [ru]

SS8028G

Micro-Power Step-up DC/DC Converter

FEATURES

Configurable output voltage up to 16V
Quiescent current of 20µA

DESCRIPTION

The SS8028G boost converter is designed for small and
medium size LCD panels requiring high bias voltages.

Shutdown current <1µA
Shutdown-pin current <1µA
Supply range from 2.5V to 6.5V
Low V

: 250mV (ISW=300mA)

DS(on)

Tiny SOT-23-5 package

With a typical quiescent current of 20µA and a supply
voltage range of 2.5V to 6.5V, it is suitable for battery
powered portable applications, such as PDAs and
handheld computers. When the SS8028G goes into
shutdown mode, it consumes less than 1µA.

APPLICATIONS

• STN/TFT LCD Bias

• Personal Digital Assistants (PDAs)

• Handheld Computers

• Digital Still Cameras

• Cellular Phones

Furthermore, with a 350mA current limit, 500ns fixed
minimum off-time and tiny SOT-23-5 package, the
SS8028G can be used with smaller inductors and other
surface-mount components to minimize the required PCB
footprint in space-conscious applications.

To control the SS8028G, no other external current is
needed for the shutdown pin, which typically consumes

• WebPad

• White LED Driver

• Local 3V to 5V Conversion

TYPICAL APPLICATION CIRCUIT

2.5V – 4.2V

4.7 µ F

4.7 µ F

10uH

VCC

VCC

SS8028G

G5111

SHDN
SHDN

GND

GND

less than 1µA over the full supply range.

RoHS compliant.

16V

SW
SW

FB
FB

1M

80.6k

12mA

1 µ F

1 µ F

Rev.2.20 4/06/2005

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Packing

G963

4 1

3

G963

4 1 2 3

ORDERING INFORMATION

SS8028GTXXXX

PIN CONFIGURATION

SS8028G

Example: SS8028GT11TR

PIN DESCRIPTIONS

PIN NAME FUNCTION

1 SW Switch pin. The drain of the internal N-MOSFET power switch. Connect this pin to the inductor.
2 GND Ground.

3 FB

4
5 VCC Input supply pin. Bypass this pin with a capacitor as close to the device as possible.

SHDN

TR: Tape and reel
TB: Tube

Pinout option

T11

à T11 pin configuration shipped in

tape and reel packing

Feedback pin. Set the output voltage by selecting values for R1 and R2 (see the Block Diagram):

OUT

V

R1 = R2
Active-low shutdown pin. Tie this pin to logic-high to enable the device, or tie it to logic-low to turn the

device off.

-1

2.1

SOT-23-5
Top view

SW

GND

FB

SS8028GT11

2

VCC

5

5

SHDN

ABSOLUTE MAXIMUM RATINGS

SW to GND…………………………………………………................……..-0.3V to +18V

FB to GND…………………………………………………….................…..-0.3V to VCC

VCC,

Operating Temperature Range.............................................................-40°C to 85°C

Maximum Operating Junction Temperature....................................................+125°C

Storage Temperature Range..............................................................-65°C to 150°C

Maximum Lead Temperature (Soldering, 10sec)............................................+300°C

Rev.2.20 4/06/2005

to GND..................................................................................-0.3V to +7V

SHDN

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ELECTRICAL CHARACTERISTICS

(V

= 3.6V, VSHDN = 3.6V, TA = 25°C)

CC

SS8028G

PARAMETER CONDITIONS MIN

Input Voltage Range

2.5 6.5 V

TYP MAX

UNITS

Not switching 20 30 µA

Quiescent Current

FB Comparator Trip Point
Output Voltage Line

V

= 0V 0.1 1 µA

SHDN

1.18 1.2 1.22

2.5V<VIN<6.5V -0.05

%/V

V

Regulation
FB Pin Bias Current

VFB = 1.2V 30 80 nA

(Note 2)

V

> 1V 500 ns

FB

Switch Off Time

Switch V

DS(ON)

V

< 0.6V 1.6 µs

FB

ISW = 300mA 250 350 mV

Switch Current Limit 300 350 400 mA

Pin Current

SHDN

Input Voltage High 0.9 V

SHDN

Input Voltage Low 0.25

SHDN

Switch Leakage Current Switch off, V

0.1 1 µA

= 16V 0.01

SW

5 µA

V

Note 1: The SS8028G is guaranteed to meet performance specifications from 0°C to 85°C.

Specifications over the -40°C to 85°C operating temperature range are assured by design,
characterization and correlation with statistical process controls.

Note 2: Bias current flows into the FB pin.

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VIN=2.7V

VOUT=16V

TYPICAL PERFORMANCE CHARACTERISTICS

SS8028G

(VCC=+3.6V, V

=+3.6V, L=10µH, TA=25°C, unless otherwise noted.)

SHDN

Efficiency vs. Load Current

90

80

70

60

50

Efficiency (%)

40

30

0.1 1 10 100

VIN=4.2V

VIN=2.7V

Load Current (mA)

Vds_on vs. Temperature

500

400

VIN=2.7V

300

VIN=3.6V

Output Voltage vs. Load Current

17

16.5

16

Output Voltage (V)

15.5

15

1 2 3 4 5 6 7 8 9 10

Load Current (mA)

Quiescent Current vs. Temperature

50

40

30

VIN=4.2V

VIN=4.2V

200

Switch Vds_on (mV)

100

-20 0 20 40 60 80 100

VIN=4.2V

Temperature (C)

FB Bias Current vs. Temperature

30

VIN=2.7V

25

20

VIN=4.2V

Feedback Bias Current (nA)

15

-20 0 20 40 60 80 100

Temperature (C)

20

Quiescent Current (µA)

10

-20 0 20 40 60 80 100

VIN=2.7V

Temperature (C)

Feedback Voltage vs. Temperature

1.22

1.21
VIN=2.7V

1.2

1.19

Feedback Voltage (V)

1.18

-20 0 20 40 60 80 100

VIN=4.2V

Temperature (C)

Rev.2.20 4/06/2005

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TYPICAL PERFORMANCE (cont.)

SS8028G

Switch Current Limit vs. Temperature

450

400

350

VIN=2.7V

Peak Current (mA)

300

250

-20 0 20 40 60 80 100

VIN=4.2V

Temperature (C)

Load Transient

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BLOCK DIAGRAM

V

V

IN

IN

VOUT

VOUT

R1

R1

R2

R2

C1

C1

FB

FB

1.2V

1.2V

BIAS

BIAS

+

+

VCC

VCC

ERROR

ERROR
COMP

COMP

VREF

VREF

SHDN

SHDN

SHUTDOWN

SHUTDOWN

LOGIC

LOGIC

en_sw

en_sw

PUMP CONTROL

PUMP CONTROL

OC

OC
COMP

COMP

+

+

T

T
CONTROL

CONTROL

OFF

OFF

L1

L1

PULSE

PULSE

DRIVER

DRIVER

GND

GND

SW

SW

SS8028G

V

V

OUT

OUT

C2

C2

APPLICATIONS INFORMATION

The SS8028G is a boost converter with an integrated
N-channel MOSFET (refer to the block diagram above).
The boost cycle is initiated when the FB pin voltage drops
below 1.2V and the MOSFET turns on. During the period
that the MOSFET is on, the inductor current ramps up
until the 350mA current limit is reached. Then the
MOSFET turns off and the inductor current flows through
the external schottky diode, ramping down to zero.
During the MOSFET off period, the inductor current
charges the output capacitor and the output voltage
climbs. This pumping mechanism continues cycle by
cycle until the FB pin voltage exceeds 1.2V and the
non-switching mode starts. In this mode, the SS8028G
consumes as little as 20uA typically, saving on battery
power.

Choosing an Inductor

There are several recommended inductors that work
well with the SS8028G in Table 1. Use the equations
and recommendations in the next few sections to find
the proper inductance value for your design.

TABLE 1. R ECOMMENDED INDUCTORS

PART VALUE

LQH3C4R7

LQH3C100
LQH3C220

CD43-4R7
CD43-100

CDRH4D18-4R7

CDRH4D18-100

DO1608-472
DO1608-103
DO1608-223

(uH) MAX DCR ?Ω)

4.7
10
22

4.7
10

4.7
10

4.7
10
22

0.26

0.30

0.92

0.11

0.18

0.16

0.20

0.09

0.16

0.37

www.murata.com

www.sumida.com

www.coilcraft.com

Inductor Selection – Boost Regulator

The appropriate inductance value for the boost regulator
application may be calculated from the following
equation. Select a standard inductor close to this value.

V

OUT-VIN(MIN)+VD

L =

I

LIM

x t

OFF

VENDOR

Murata

Sumida

Coilcraft

Rev.2.20 4/06/2005

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Here, VD = 0.4V (Schottky diode voltage), I
and t
increase the available output current, but limit it to about
twice the calculated value. When too large an inductor is
used, the output voltage ripple will increase without
providing much additional output current. In conditions of
varying V
minimum V
value can be used to give smaller physical size, but
overshoot of the inductor current will occur (see Current
Limit Overshoot section).

= 500ns. A larger value can be used to slightly

OFF

, such as battery power applications, use the

IN

value in the above equation. A smaller

IN

LIM

Inductor Selection – SEPIC Regulator

For a SEPIC regulator using the SS8028G, the
approximate inductance value can be calculated using
the formula below. As for the boost inductor selection, a
larger or smaller value can be used.

Current Limit Overshoot

The SS8028G uses a constant off-time control scheme;
the MOSFET is turned off after the 350mA current limit is
reached. When the current limit is reached and the
MOSFET actually turns off, there is a 100ns delay time.
During this time, the inductor current exceeds the current
limit by a small amount. The formula below can calculate
the peak inductor current.

L = 2

I

PEAK

= I

LIM

+

V

OUT

V

+ V

I

LIM

IN(MAX)

x t

D

OFF

– V

SAT

x 100ns

L

Here, V

= 0.25V (switch saturation voltage). For

SAT

systems with high input voltages and smaller
inductance values, the current overshoot will be most
apparent. This overshoot can be useful as it helps
increase the amount of available output current. By
using a small inductance value, the current limit
overshoot can be quite high. Even though it is
internally current limited to 350mA, the internal
MOSFET of the SS8028G can handle larger currents

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= 350mA

SS8028G

without any problem, but the total efficiency will suffer.
For best performance, the I
500mA.

Capacitor Selection

Low ESR (Equivalent Series Resistance) capacitors
should be used at the output to minimize the output
ripple voltage and the peak-to-peak transient voltage.
Multilayer ceramic capacitors (MLCC) are the best
choice, as they have a very low ESR and are
available in very small packages. Their small size
makes them a good match with the SS8028G’s
SOT-23 package. If solid tantalum capacitors (like the
AVX TPS, Sprague 593D families) or OS-CON
capacitors are used, they will occupy more volume
than ceramic ones and the higher ESR increases the
output ripple voltage. It is important to use a capacitor
with a sufficient voltage rating.
A low ESR surface-mount ceramic capacitor also
makes a good selection for the input bypass capacitor,
which should be placed as close as possible to the
SS8028G. A 4.7µF input capacitor is sufficient for
most applications.

Diode Selection

For most SS8028G applications, the high switching
frequency requires high-speed Schottky diodes, such
as the Motorola MBR0530 (0.5A, 30V) with their low
forward voltage drop and fast switching speed. Many
different manufacturers make equivalent parts, but
make sure that the component is rated for at least

0.35A. To achieve high efficiency, the average
current rating of the Schottky diodes should be
greater than the peak switching current. Choose a
reverse breakdown voltage greater than the output
voltage.

Lowering Output Ripple Voltage

The SS8028G supplies energy to the load in bursts by
ramping up the inductor current, then delivering that
current to the load. Using low ESR capacitors will help

is best kept below

PEAK

C2 22

D1

C2 22

10

C2 22

D1

C2 22

L1:MURATA LQH3C4R7M24

L1,L2:MURATA LQH3C100K24

10

minimize the output ripple voltage, but proper
selection of the inductor and the output capacitor also
plays a big role. If a larger inductance value or a
smaller capacitance value is used, the output ripple
voltage will increase because the capacitor will be
slightly overcharged each burst cycle. To reduce the

TYPICAL APPLICATION CIRCUITS

SS8028G

output ripple, increase the output capacitance value,
or add a 10pF feed-forward capacitor in the feedback
network of the SS8028G (see the circuits in the
Typical Applications section). To add this small
inexpensive 10pF capacitor will greatly reduce the
output voltage ripple.

V

2.5V to 4.2V

Boost Converter SEPIC Converter

GND

GND

C3

D1:MOTOROLA MBR0520

1uF

1

SW

L2

L2

FB

D1

D1

µ H

µ H

IN

2.5V~5.5V

2.5V~5.5V

VCC

VCC

SHDN

C1

C1

4.7 µ F

4.7 µ F

VBAT

VBAT

ON/OFF Control

ON/OFF Control

SHDN

C1

C1

4.7µF

4.7µF

L1

4.7uH

G5111

GND

GND

D1:MOTOROLA MBR0520

SW

10µH/0.5A

10µH/0.5A

VCC

VCC

390k
R1

120k
R2

SW

FB
FB

SS8028G

SHDN

SHDN FB

L1
10uH

V

5 V

5 V
50mA

50mA

µ F

µ F

L1

L1

SW

SW

FB

D1

D1

MBR0520

MBR0520

2.5V to 4.2V

IN

VCC

SHDN

C1

C1

4.7 µ F

4.7 µ F

C2

C2
1µF

1µF

D2(Optional)

D2(Optional)
18V

18V

470k

R1

270k

R2

3.3 V

3.3 V
60mA

60mA

µ F

µ F

White LED Driver

Rev.2.20 4/06/2005

GND

GND

VBIAS(+3.3V)

VBIAS(+3.3V)

PWM Dim

PWM Dim

PWM Dimming Control

PWM Dimming Control
VH=3.3V

VH=3.3V
VL=0V

VL=0V
Freq=160~240Hz

Freq=160~240Hz

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R3

R3

308k_1%

308k_1%

R4

R4

660k_1%

660k_1%

R2

R2

120k_1%

120k_1%

R1

R1
30_1%

30_1%

Dimming Ratio>50:1

Dimming Ratio>50:1
Drive 2~4 White LEDs

Drive 2~4 White LEDs

SS8028G

PACKAGE DIMENSIONS

SOT-23-5 (unit: mm)

D

D

H

H

E

E

e1

e1

e

e

A

A2

A2

b

b

A

A1

A1

1. Package body sizes exclude mold flash protrusions or gate burrs

2. Tolerance ±0.1000 mm (4mil) unless otherwise specified

3. Coplanarity: 0.1000mm

4. Dimension L is measured in gage plane

C

C

L

L

θ1

θ1

SYMBOLS

A 1.00 1.10 1.30
A1 0.00 ----- 0.10
A2 0.70 0.80 0.90

b 0.35 0.40 0.50

C 0.10 0.15 0.25

D 2.70 2.90 3.10

E 1.40 1.60 1.80

e ----- 1.90(TYP) ----­e1 ----- 0.95 -----

H 2.60 2.80 3.00

L 0.37 ------ ----­?1 1º 5º 9º

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responsibility for its use, or for infringement of any patent or other intellectual property rights of third parties that may result from its
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without limitation enhancement in reliability, functionality or design. No license is granted, whether expressly or by implication, in relation to
the use of any products described herein or to the use of any information provided herein, under any patent or other intellectual property rights of
Silicon Standard Corporation or any third parties.

DIMENSIONS IN MILLIMETERS

MIN

SOT23-5 Package Orientation

SOT23-5 Package Orientation

NOM MAX

Feed Direction

Feed Direction

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