LP8557, LP85571

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SNVSA15B – DECEMBER 2013 – REVISED DECEMBER 2015

7.5 Electrical Characteristics

Unless otherwise specified: TA = 25°C, VDD = 3.8 V.

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNIT

VDD

Input voltage range

2.7

5.5

V

IDDQ

Standby current

1

µA

IDD

Operating current

No current going through LEDs

2.2

mA

Internal oscillator frequency

–4%

4%

ƒOSC

accuracy

–7%(1)

7%(1)

TTSD

Thermal shutdown threshold(2)

150

°C

TTSD_hyst

Thermal shutdown hysteresis(2)

20

(1)

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

≤ TA ≤ 85°C.

(2)

Verified by design and not tested in production.

7.6 Boost Converter Electrical Characteristics

Unless otherwise specified: TA = 25°C, VDD = 3.8 V

(1).

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNIT

RDS_ON

Switch ON resistance

ISW = 0.5 A

0.2

Ω

VBOOST_MIN

Minimum output voltage

6(2)

7

8(2)

V

VBOOST_MAX

Maximum output voltage

27(2)

28

29(2)

V

ISW_CL

SW pin current limit

2.1

2.4

2.5

A

ISW_LIM = 2.4 A

ILOAD_MAX

Maximum continuous load current (3)

160

mA

VIN = 3 V, VOUT = 24 V

500

ƒSW

Switching frequency

kHz

1000

Overvoltage protection voltage

VBOOST_MAX

VOVP_TH

threshold

+ 1.6

V

VUVLO_TH

UVLO threshold

2.5

VUVLO_hyst

UVLO hysteresis

50

mV

tPULSE

Switch pulse minimum width (3)

No load

80

ns

tSTARTUP

Boost start-up time (3)

1

ms

(1)

Minimum (Min) and Maximum (Max) limits are specified by design, test, or statistical analysis.

(2)

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

≤ TA ≤ 85°C.

(3)

Verified by design and not tested in production.

7.7 LED Driver Electrical Characteristics (LED1 To LED6 Pins)

Unless otherwise specified: TA = 25°C, VDD = 3.8 V

(1).

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNIT

ILEAKAGE

Leakage current

Outputs LED1...LED6, VOUT = 28 V

1

µA

ILED_MAX

Maximum sink current LED1...6

25

mA

–3%

3%

ILED_ACC

LED current accuracy(2)

Output current set to 20 mA

–4%(3)

4%(3)

IMATCH

Channel to Channel Matching (2)

Output current set to 20 mA

0.5

PFREQ = 000b

4.9

ƒLED

LED switching frequency(4)

kHz

PFREQ = 111b

39.1

VSAT

Saturation voltage(5)

Output current set to 20 mA

200

mV

(1)

Minimum (Min) and Maximum (Max) limits are specified by design, test, or statistical analysis.

(2)

The LED current accuracy is defined as 100 × (ILED_AVE – ILED_Target) / ILED_AVE. The channel-to-channel LED current matching

is defined as (ILED_MAX – ILED_MIN) / ILED_AVE.

(3)

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

≤ TA ≤ 85°C.

(4)

Verified by design and not tested in production.

(5)

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

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