LP8550

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SNVS657E – SEPTEMBER 2010 – REVISED SEPTEMBER 2014

7.7

LED Driver Electrical Characteristics

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNIT

ILEAKAGE

Leakage current

Outputs OUT1 to OUT6, VOUT = 40 V

0.1

1

μA

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

30

Maximum source current OUT1 to

IMAX

mA

OUT6

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

50

Output current set to 23 mA, EN_I_RES

–3%

3%

IOUT

Output current accuracy(1)

= 1

-4%(2)

4%(2)

Output current set to 23 mA, EN_I_RES

IMATCH

Matching(1)

0.5%

= 1

fLED = 5 kHz, fPLL = 5 MHz

10

fLED = 10 kHz, fPLL = 5 MHz

9

fLED = 20 kHz, fPLL = 5 MHz

8

PWMRES

PWM output resolution(3)

bits

fLED = 5 kHz, fPLL = 40 MHz

13

fLED = 10 kHz, fPLL = 40 MHz

12

fLED = 20 kHz, fPLL = 40 MHz

11

PWM_FREQ[4:0] = 00000b

600

PLL clock 5 MHz

fLED

LED switching frequency(3)

Hz

PWM_FREQ[4:0] = 11111b

19.2k

PLL clock 5 MHz

Output current set to 20 mA

105

220(5)

VSAT

Saturation voltage(4)

mV

Output current set to 30 mA

160

290(5)

(1)

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 OUT6), 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.

(2)

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

≤ TA ≤ 85°C).

(3)

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

(4)

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

(5)

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

≤ TA ≤ 85°C).

7.8

PWM Interface Characteristics

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNIT

fPWM

PWM frequency range

0.1

25

kHz

tMIN_ON

Minimum pulse ON time

1

μs

tMIN_OFF

Minimum pulse OFF time

1

Turnon delay from standby to

PWM input active, EN pin rise from low to

tSTARTUP

6

ms

backlight on

high

PWM input low time for turn off, slope

TSTBY

Turn off delay

50

ms

disabled

fIN < 9 kHz

10

fIN < 4.5 kHz

11

PWMRES

PWM input resolution

bits

fIN < 2.2 kHz

12

fIN < 1.1 kHz

13

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