LP8551TLXSLASHNOPB datasheet(7/47 Pages) TI1

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LP8551

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SNVS673E – APRIL 2010 – REVISED SEPTEMBER 2014

7.7 LED Driver Electrical Characteristics

Limits are for TA = 25°C and VIN = 12 V, VDDIO = 2.8 V, CVLDO = 1 μF, L1 = 15 μH, CIN = 10 μF, COUT = 10 μF, unless

otherwise specified. RISET = 16 kΩ

(1)

SYMBOL

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNIT

ILEAKAGE

Leakage current

Outputs OUT1...OUT4, VOUT = 40 V

0.1

μA

EN_I_RES = 0, CURRENT[7:0] = FFh

Maximum source current

IMAX

OUT1...OUT4

EN_I_RES = 1, CURRENT[7:0] = FFh

–3%

IOUT

Output current accuracy(2)

Output current set to 23 mA, EN_I_RES = 1

–4%(3)

4%(3)

IMATCH

Matching(2)

Output current set to 23 mA, EN_I_RES = 1

0.5%

fLED = 5 kHz, fPLL = 5 MHz

fLED = 10 kHz, fPLL = 5 MHz

fLED = 20 kHz, fPLL = 5 MHz

PWMRES

PWM output resolution(4)

bits

fLED = 5 kHz, fPLL = 40 MHz

fLED = 10 kHz, fPLL = 40 MHz

fLED = 20 kHz, fPLL = 40 MHz

PWM_FREQ[4:0] = 00000b

600

PLL clock 5 MHz

fLED

LED switching frequency(4)

PWM_FREQ[4:0] = 11111b

19.2k

PLL clock 5 MHz

Output current set to 20 mA

105

220(3)

VSAT

Saturation voltage(5)

Output current set to 30 mA

160

290(3)

(1)

Low-ESR surface-mount ceramic capacitors (MLCCs) used in setting electrical characteristics.

(2)

Output Current Accuracy is the difference between the actual value of the output current and programmed value of this current.

Matching is the maximum difference from the average. For the constant current sinks on the part (OUT1 to OUT4), the following are

determined: the maximum output current (MAX), the minimum output current (MIN), and the average output current of all outputs (AVG).

Two matching numbers are calculated: (MAX-AVG)/AVG and (AVG-MIN/AVG). The largest number of the two (worst case) is

considered the matching figure. The typical specification provided is the most likely norm of the matching figure for all parts. Note that

some manufacturers have different definitions in use.

(3)

Limits apply over the full operating ambient temperature range (–30°C

≤ TA ≤ 85°C).

(4)

PWM output resolution and frequency depend on the PLL settings. Please see section PWM Frequency Setting for full description.

(5)

Saturation voltage is defined as the voltage when the LED current has dropped 10% from the value measured at 1 V.

7.8 PWM Interface Characteristics

Limits are for TA = 25°C and VIN = 12 V, VDDIO = 2.8 V, CVLDO = 1 μF, L1 = 15 μH, CIN = 10 μF, COUT = 10 μF, unless

otherwise specified. RISET = 16 kΩ

(1)

SYMBOL

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNIT

ƒPWM

PWM frequency range

0.1

kHz

tMIN_ON

Minimum pulse ON time

μs

tMIN_OFF

Minimum pulse OFF time

Turnon delay from standby to

PWM input active, EN pin rise from low to

tSTARTUP

backlight on

high

PWM input low time for turn off, slope

TSTBY

Turnoff Delay

disabled

ƒIN < 9 kHz

ƒIN < 4.5 kHz

PWMRES

PWM Input Resolution

bits

ƒIN < 2.2 kHz

ƒIN < 1.1 kHz

(1)

Low-ESR surface-mount ceramic capacitors (MLCCs) used in setting electrical characteristics.

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