SP4446EK-L - EXAR - Product.Network

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SP4446

FEATURES

■ High Output Voltage: Up to 30V

■ High Efficiency

■ Low Quiescent Current: ~20uA

■ Single Battery Cell Operation

■ Programmable Output Voltage

■ 1Ω Switch (150mV at 150mA)

■ Lead Free, RoHS Compliant

Package: 5 Pin SOT-23

High Output Volta ge Boost Regulator

LCD Bias Regulator

The SP4446 is a micro power Boost Regulator in a 5-lead SOT-23 package. It is a current

limited, fixed off-time regulator configured for use in boost mode applications. The operating

voltage can be less than 3Volts and is capable of generating voltages as high as 30Volts.

The SP4446 is available in a Lead Free, RoHS compliant package and permits the construction

of complete regulators that occupy < 0.2 square inches of board space.

TYPICAL APPLICATION SCHEMATIC

5 4

1 2 3

SP4446

VIN SHDN

SW GND FB

5 Pin SOT-23

V

IN

SW

GND

SHDN FB

10µH

D1

L1

R1

R2

C2

2.2 µF

High

Voltage Output

V

IN

4.7µF

C1

2 to 7V

SP4446

APPLICATIONS

■ LCD Bias

■ Tuner Pin Voltage

■ White LED Driver

■ High Voltage Bias

■ Digital Cameras

■ Cell Phone

■ Battery Backup

■ Handheld Computers

DESCRIPTION

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PIN DESCRIPTION

VIN ....................................................................... 15V

SW Voltage .............................................. -0.4 to 34V

FB Voltage .......................................................... 2.5V

All other pins .................................. -0.3 to VCC + 0.3V

Current into FB ................................................. ±1mA

TJ Max ............................................................. 125°C

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

Peak Output Current < 10us SW .................... 500mA

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

Power Dissipation. ......................................... 200mW

PARAMETER SYMBOL MIN TYP MAX UNITS CONDITIONS

Input voltage VIN 1.0 8.0 V Switch Current Limit =

150mA

Supply Current IQ 20 30 µA ♦No Switching

0.01 1 µA SHDN = 0.0V

Reference Voltage VFB 1.17 1.22 1.27 V ♦

FB Hysteresis HYST 8 mV

VFB Input Bias Current IFB 15 80 nA ♦VFB = 1.22V

Line Regulation ∆Vo/∆VI 0.04 %/V 1.2 ≤ VIN ≤ 8V

Switch Off Time TOFF 300 nS VFB > 1V

1200 nS VFB < 0.3V

Switch Saturation Voltage VCESAT 50 mV ♦ISW = 50mA

150 mV ISW = 150m A

Switch Current Limit ILIM 100 150 200 mA ♦

SHDN Bias Current ISHDN 5 12 µA ♦VSHDN = 5V

SHDN High Threshold (on) VIH 0.9 V

SHDN Low Threshold (off) VIL 0.25 V

Switch Leakage Current ISWLK 2 5 µA ♦Switch Off, VSW = 5V

ELECTRICAL CHARACTERISTICS

Specifications are at VIN = 3.3V, VSHDN = VIN, TA = 25°C, ♦ denotes the specifications which apply over the full operating

temperature range, unless otherwise specified.

ABSOLUTE MAXIMUM RATINGS

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

ESD Rating ................................................. 2kV HBM

These are stress ratings only and functional operation of

the device at these ratings or any other above those

indicated in the operation sections of the specifications

below is not implied. Exposure to absolute maximum

rating conditions for extended periods of time may affect

reliability.

PIN NUMBER PIN NAME DESCRIPTION

1 SW Switch input to the internal power switch.

2 GND Ground

3 FB Feed back

4 SHDN Shutdown. Pull high (on) to enable. Pull low (off) for shutdown.

5 VIN Input Voltage. Bypass this pin with a capacitor as close to the device

as possible.

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FUNCTIONAL DIAGRAM

+

-

VI

(EXTERNAL)

R1

R2

C1

SHDN 4

Q1 Q2

R3

R4

R6

R5 X1

Shutdown

Logic

300ns

ONE-SHOT

CLEAR

X2 +

-

SET

DRIVER

52.5mV

0.35

GND

2

15

3

L1

SW C2

D1 V

OUT

POWER

TRANSISTOR

DISABLE

V

IN

FB

General Overview:

Operation can be best understood by referring to

the above block diagram. Q1 and Q2 along with

R3 and R4 form a band gap reference. The input

to this circuit completes a feedback path from

the high voltage output through a voltage di-

vider, and is used as the regulation control input.

When the voltage at the FB pin is slightly above

1.22V, comparator X1 disables most of the

internal circuitry. Current is then provided by

capacitor C2, which slowly discharges until the

voltage at the FB pin drops below the lower

hysteresis point of X1, about 6mV. X1 then

enables the internal circuitry, turns on chip

power, and the current in the inductor begins to

ramp up. When the current through the driver

transistor reaches about 150mA, comparator X2

clears the latch, which turns off the driver tran-

sistor for a preset 0.3µs. At the instant of shutoff,

inductor current is diverted to the output through

diode D1. During this 0.3µs time limit, inductor

current decreases while its energy charges C2.

THEORY OF OPERATION

At the end of the 0.3µs time period, the driver

transistor is again allowed to turn on which

ramps the current back up to the 150mA level.

Comparator X2 clears the latch, its output turns

off the driver transistor, and this allows delivery

of inductor L1’s stored kinetic energy to C2.

This switching action continues until the output

capacitor voltage is charged to the point where

FB is at band gap (1.22V). When this condition

is reached, X1 turns off the internal circuitry and

the cycle repeats. The SP4446 contains circuitry

to provide protection during startup and while in

short-circuit conditions. When FB pin voltage is

less than approximately 300mV, the switch off

time is increased to about 1.2µs and the current

limit is reduced to about 70% of its normal

value. While in this mode, the average inductor

current is reduced and helps minimize power

dissipation in the SP4446, the external inductor

and diode.

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inherently low ESR, which will help produce low

peak to peak output ripple, and reduce high fre-

quency spikes.

For the typical application, a 4.7µF input capacitor

and a 2.2µF output capacitor are sufficient. The

input and output ripple could be further reduced by

increasing the value of the input and output capaci-

tors. Place all the capacitors as close to the SP4446

as possible for layout. For use as a voltage source,

to reduce the output ripple, a small feedforward

capacitor (47pF) across the top feedback resistor

can be used to provide sufficient overdrive for the

error comparator, thus reduce the output ripple.

Refer to Table 2 for some suggested low ESR capacitors.

MANUF. PART CAP/ SIZE/

NUMBER VOLTAGE TYPE

MURATA GRM32RR71E 2.2µF/25V 1210/X5R

770-436-1300 225KC01B

MURATA GRM31CR61A 4.7µF/10V 1206/X5R

770-436-1300 475KA01B

TDK C3225X7R1E 2.2µF/25V 1206/X7R

847-803-6100 225M

TDK C3216X5R1A 4.7µF/10V 1206/X5R

847-803-6100 475K

APPLICATION INFORMATION

Inductor Selection

For SP4446, the internal switch will be turned off

only after the inductor current reaches the typical

DC current limit (ILIM=150mA). However, there is

typically a propagation delay of 200nS between

the time when the current limit is reached and

when the switch is actually turned off. During this

200nS delay, the peak inductor current will in-

crease, exceeding the current limit by a small amount.

The peak inductor current can be estimated by:

IPK = ILIM + VIN(MAX) • 200nS

L

The larger the input voltage and the lower the

inductor value, the greater the peak current.

In selecting an inductor, the saturation current

specified for the inductor needs to be greater than

the SP4446 peak current to avoid saturating the

inductor, which would result in a loss of efficiency

and could damage the inductor. Choosing an in-

ductor with low DCR decreases power losses and

increase efficiency.

Refer to Table 1 for some suggested low ESR inductors.

MANUF. PART NUMBER DCR Current

(

Ω

) Rating

(mA)

MURATA LQH32CN100K21 0.44 300

770-436-1300 (10µH)

MURATA LQH32CN220K21 0.71 250

770-436-1300 (22µH)

TDK NLFC453232T-100K

847-803-6100 (10µH) 0.273 250

TDK NLC453232T-100K 0.9 370

847-803-6100 (22µH)

Table 1. Suggested Low ESR inductors

Diode Selection

A schottky diode with a low forward drop and fast

switching speed is ideally used here to achieve

high efficiency. In selecting a Schottky diode, the

current rating of the schottky diode should be

larger than the peak inductor current. Moreover,

the reverse breakdown voltage of the Schottky

diode should be larger than the output voltage.

Capacitor Selection

Ceramic capacitors are recommended for their

Table 2. Suggested Low ESR Capacitor

Output Voltage Program

In order for the SP4446 to be programmed as a

voltage source, the SP4446 requires 2 feedback

resistors R 1 & R2 t o control th e output vo ltage, as

shown in Figure 1.

L1

1.22V

R2

D1

C1

C2 R1

VOUT

U1

SP4446

1

2

34

5

SW

G

ND

FBSHDN

V

IN

VIN

Figure 1. Using SP4446 as Voltage Source

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APPLICATION INFORMATION: Continued

The formula and table for the resistor selection

are shown below:

R1 =( VOUT - 1 ) • R2

1.22

VOUT (V) R1 (Ω) R2 (Ω)

12 1M 113K

15 1M 88.7K

18 1M 73.2K

20 1M 64.9K

30 1M 42.2K

Table 3. Divider Resistor Selection

Layout Considerations

Both the input capacitor and the output capacitor

should be placed as close as possible to the IC. This

can reduce the copper trace resistance which di-

rectly effects the input and output ripple. The

feedback resistor network should be kept close to

the FB pin to minimize copper trace connections

that can inject noise into the system. The ground

connection for the feedback resistor network should

connect directly to the GND pin or to an analog

ground plane that is tied directly to the GND pin.

The inductor and the Schottky diode should be

placed as close as possible to the switch pin to

minimize the noise coupling to the other circuits,

especially the feedback network.

PIN Diode Driver

The SP4446 can be used as PIN diode driver as

shown in Figure. 2.

Fig. 2. Pin Diode Driver

3.3V or 5V

R1

1M

C1

4.7uF

30V

R2

42.2K

U1

SP4446

1

2

34

5

SHDN

Murata LQH32CN100K21

3 to 5 mA

DS

MBR0530

C2

47pF

1.22V

L1 10uH 0.3A

C3

2.2uF

3.3V or 5V

R1

1M

C1

4.7uF

30V

R2

42.2K

U1

SP4446

1

2

34

SW

GND

FBSHDN

V

IN

Murata LQH32CN100K21

V

IN

3 to 5 mA

DS

MBR0530

V

OUT

C2

47pF

1.22V

L1 10uH 0.3A

C3

2.2uF

V

IN

DS

C1

4.7uF

Q1

MMBT2907A

R1

1M

R3

154K

20V

1.22V

C2

47pF

R2

64.9K

U1

SP4446

1

2

34

5

SW

GND

FBSHDN

V

IN

V

OUT

L1

10uH

C3

2.2uF

When the SP4446 is active, the voltage set at the

emitter of the transistor exceeds the input volt-

age, forcing the transistor into the saturation

region. When the SP4446 is shut down, the input

voltage exceeds the emitter voltage, thus the

transistor becomes inactive and provides high-

impedance isolation between the input and load.

Efficiency will be slightly sacrificed because of

the saturation voltage and base current of the PNP

transistor.

Fig. 3. Load Disconnect in Shutdown

Tw o R e si st o rs (R 1=1MΩ, R2=42.2KΩ) are used

to program the output voltage to be 30V. When

input voltage is 3.3V or 5V, it can supply a

maximum current of 3mA and 5mA to the load.

Load Disconnect in Shutdown

When SP4446 is shut down, the load is still

connected to the input. In applications that re-

quire output isolation during shutdown, an ex-

ternal PNP transistor (for example MMBT2907A)

can be added as shown in Figure 3.

SHDN_N

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Figure 8. 18V Output Efficiency (VIN=3.3V) Figure 9. 18V Output Efficiency (VIN=5V)

Figure 6. 15V Output Efficiency (VIN=3.3V) Figure 7. 15V Output Efficiency (VIN=5V)

Vin=3.3V; Vout = 18V Efficiency

40

45

50

55

60

65

70

75

80

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0

Iout (mA)

Efficiency (%)

10 uH

22 uH

Vin=5.0V; Vout = 18V Efficiency

40

45

50

55

60

65

70

75

80

0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0

Iout (mA)

Efficiency (%)

10 uH

22 uH

PERFORMANCE CHARACTERISTICS

Refer to the typical application circuit, TAMB = 25°C, unless otherwise specified.

Figure 4. 12V Output Efficiency (VIN=3.3V) Figure 5. 12V Output Efficiency (VIN=5V)

Vin=3.3V;Vout =12V Efficiency

50

55

60

65

70

75

80

85

0 3 6 9 12 15 18

Iout (mA)

Efficiency (%)

10 uH

22 uH

Vin=5.0V;Vout =12V Efficiency

50

55

60

65

70

75

80

85

0 5 10 15 20 25 30

Iout (mA)

Efficiency (%)

10 uH

22 uH

Vin=3.3V;Vout =15V Efficiency

50

55

60

65

70

75

80

0 2 4 6 8 10 12

Iout (mA)

Efficiency (%)

10 uH

22 uH

Vin=5.0V;Vout =15V Efficiency

50

55

60

65

70

75

80

0 3 6 9 12 15 18

Iout (mA)

Efficiency (%)

10 uH

22 uH

7

Vin=3.3V;Vout = 20V Efficiency

30

35

40

45

50

55

60

65

70

75

0 1 2 3 4 5 6 7

Iout (mA)

Efficiency (%)

10 uH

22 uH

Vin=5V;Vout = 20V Efficiency

35

40

45

50

55

60

65

70

75

0 2 4 6 8 10 12

Iout (mA)

Efficiency (%)

10 uH

22 uH

PERFORMANCE CHARACTERISTICS

Refer to the typical application circuit, TAMB = 25°C, unless otherwise specified.

Figure 10. 20V Output Efficiency (VIN=3.3V) Figure 11. 20V Output Efficiency (VIN=5V)

Figure 12. Maximum Output Current vs. VIN (V

OUT=20V) Figure 13. Maximum Output Current vs. VIN (VOUT=30V)

0

2

4

6

8

10

12

2.7 3 3.3 3.6 3.9 4.2 4.5 4.8 5.1

Input Voltage (V)

Maximum Output Current (mA)

10uH

22uH

0

1

2

3

4

5

6

2.7 3 3.3 3.6 3.9 4.2 4.5 4.8 5.1

Input Voltage (V)

Maximum Output Current (mA)

10uH

22uH

0

5

10

15

20

25

30

1 2 3 4 5 6 7 8

Input Voltage (V)

Quiescent Current (uA)

Tamb=-40°C

Tamb=25°C

Tamb=85°C

0

2

4

6

8

10

1 2 3 4 5 6 7 8

Input Voltage (V)

Shutdown Pin Current (uA)

Figure 14. Quiescent Current IQ vs. VIN Figure 15. Shutdown Pin Current vs. VIN

8

V

OUT

(AC)

I

OUT

(5mA/DIV)

V

SW

V

OUT

(AC)

I

L

(0.1A/DIV)

V

SW

VIN

VOUT

IIN (100mA/DIV)

Figure 19. Startup Waveform (VIN=3.3V, VOUT=20V,

IOUT=2mA)

Figure 20. Typical Switching Waveforms (VIN=3.3V,

VOUT=20V, IOUT=5mA) Figure 21. Load Step Transient (VIN=3.3V, VOUT=20V,

1O=100µA∼5mA)

Figure 16. IPK Current Limit vs. VIN Figure 17. Feedback Voltage vs. Temperature

0

50

100

150

200

250

1 2 3 4 5 6 7 8

Input Voltage (V)

Ipk Current Limit (mA)

1.18

1.19

1.20

1.21

1.22

1.23

1.24

1.25

-40 -15 10 35 60 85

Temperature (C)

Feedback Voltage (V)

PERFORMANCE CHARACTERISTICS

Refer to the typical application circuit, TAMB = 25°C, unless otherwise specified.

Figure 18. Switch Saturation Voltage VCESAT vs.

Temperature (ISW=50mA)

0

10

20

30

40

50

60

-40 -15 10 35 60 85

Temperature (C)

Switch Saturation Voltage (mV)

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PACKAGE: 5 PIN SOT-23

10

Exar Corporation reserves the right to make changes to any products described herein. Sipex does not assume any liability arising out of the

application or use of any product or circuit described herein; neither does it convey any license under its patent rights nor the rights of others.

Exar Corporation

Headquarters and

Sales Office

248720 Kato Rd,33 South Hillview Drive

M Fremont, CA 94538

TEL: (510) 668-7000

FAX: (510) 668-7001

ORDERING INFORMATION

Part Number Operating Temperature Range Package Type

SP4446EK-L .................................................. -40°C to +85°C ...................................Lead Free 5 Pin SOT-23

SP4446EK-L/TR ............................................ -40°C to +85°C ...................................Lead Free 5 Pin SOT-23

-G: “Green”/Halogen free package. Substitute “-L” by “-G” in the ordering part number.

/TR = Tape and Reel

Pack quantity is 2,500 for SOT-23.