34845A datasheet(6/21 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

34845

ELECTRICAL CHARACTERISTICS

STATIC AND DYNAMIC ELECTRICAL CHARACTERISTICS

BOOST (CONTINUED)

Line Regulation

VIN = 7.0 V to 21 V, ICH = 30 mA

ILED/VIN

-0.2

0.2

%/V

Load Regulation

VLED = 24 V to 40 V (all Channels), ICH = 30 mA

ILED/VLED

-0.2

0.2

%/V

Minimum Duty Cycle

DMIN

Maximum Duty Cycle

DMAX

OVP Internally Fixed Value

(no external voltage resistor divider)

VOVP_INT

OVP Programming Range(9)

(set through an external resistor divider)

VOVP_EXT

OVP Reference Voltage

VREF_OVP

6.3

6.9

7.5

OVP Sink Current

ISINK_OVP

0.2

μA

Switching Frequency

34845

34845A

34845B

540

1080

270

600

1200

300

660

1320

330

kHz

Soft Start Time (Fs=600 kHz, 100% PWM duty)

tSS

3.0

Soft Start VOUT Overshoot (Fs=600 kHz, 100% PWM duty)

SS_VOUT

OVP

Boost Switch Rise Time

BOOST_tR

8.0

Boost Switch Fall Time

BOOST_tF

6.0

Current sense Amplifier Gain

ACSA

9.0

OTA Transconductance

200

μS

Transconductance Sink and Source Current Capability

ISS

100

μA

Slope Compensation

34845

34845A

34945B

VSLOPE

0.52

0.73

0.22

μs

LED DRIVER

LED Driver Sink Current

RISET = 51 kΩ 0.1%, PWM = 3.3 V

RISET = 5.1 kΩ 0.1%, PWM = 3.3 V

ILED

2.88

29.4

3.0

3.12

30.6

ISET Pin Voltage

RISET = 5.1 kΩ 0.1%

VISET

2.011

2.043

2.074

Regulated Minimum Voltage Across LED Drivers

Pulse Width > 400ns

VMIN

0.675

0.75

0.825

LED Current Channel to Channel Tolerance

10 mA

≤ ILED ≤ 30 mA

3.0 mA

≤ ILED < 10 mA

ITOLERANCE

-2.0

-4.0

2.0

4.0

Notes

The OVP level must be set 5.0 V above the worst-case LED string voltage.

Table 3. Static and Dynamic Electrical Characteristics (continued)

Characteristics noted under conditions VIN = 12 V, VOUT = 35 V, ILED = 30 mA, fS = 600 kHz, fPWM = 600 Hz - 40°C ≤ TA ≤

°C, unless otherwise noted. Typical values noted reflect the approximate parameter means at TA = 25°C under nominal

conditions, unless otherwise noted.

Characteristic

Symbol

Min

Typ

Max

Unit

34845A Datasheet(PDF) 6 Page - Freescale Semiconductor, Inc

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