+

-

+

-

+

-

+

-

V

OUT

V

IN

FB

SW

R

S

R

R

R

Duty control

1 MHz clock

OVPCOMP

ERRORAMP

SLOPER

OLPCOMP

RESETCOMP

LOOPC

+

-

ACTIVE

LOAD

SWITCH

+

-

UVCOMP

2V

+

-

R

IMAX

OCPCOMP

R

LP3958

www.ti.com

SNVS423C – JANUARY 2006 – REVISED MARCH 2013

Figure 3. Boost Converter Topology

MAGNETIC BOOST DC/DC CONVERTER ELECTRICAL CHARACTERISTICS

Symbol

Parameter

Test Conditions

Min

Typ

Max

Unit

ILOAD

Maximum Continuous Load

3.0V = VIN

70

mA

Current

VOUT = 18V

VOUT

Output Voltage Accuracy

3.0V

≤ VIN ≤ 5.5V

−3.5

+3.5

%

(FB Pin)

VOUT = 18V

RDSON

Switch ON Resistance

ISW = 0.5A

0.15

0.3

Ω

fPWM

PWM Mode Switching

RT = 82 k

Ω

1.0

MHz

Frequency

Frequency Accuracy

RT = 82 k

Ω

−7

+7

%

−9

+9

tPULSE

Switch Pulse Minimum

no load

45

ns

Width

tSTARTUP

Startup Time

Boost startup from STANDBY to VOUT = 18V,

15

ms

no load

IMAX

SW Pin Current Limit

800

1150

mA

BOOST STANDBY MODE

User can set the Boost Converter to STANDBY mode by writing the register bit EN_BOOST low. When

EN_BOOST is written high, the converter starts for 20ms in low current PWM mode and then goes to normal

PWM mode. All LED outputs are off during the 20ms delay to ensure smooth startup.

BOOST OUTPUT VOLTAGE CONTROL

User can control the boost output voltage by Boost Output 8-bit register.

Boost Output [7:0]

Boost Output

Register 0DH

Voltage (typical)

Bin

Dec

0000 1000

8

8.0V

0000 1001

9

9.0V

0000 1010

10

10.0V

0000 1011

11

11.0V

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