LM2756

SNVS504C – JULY 2007 – REVISED MAY 2013

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Electrical Characteristics

(1)(2) (continued)

Limits in standard typeface are for TJ = 25°C, and limits in boldface type apply over the full operating temperature range.

Unless otherwise specified: VIN = 3.6V; VHWEN = VIN; VDxA = VDxB = VDxC = 0.4V; RSET = 11.8kΩ; GroupA = GroupB = GroupC

= Fullscale Current; ENA, ENB, ENC Bits = “1”; SD53, SD62, 53A, 62A Bits = "0"; C1 = C2 = CIN= COUT= 1.0µF;

Specifications related to output current(s) and current setting pins (IDxx and ISET) apply to GroupA and GroupB.

(3)

Specifications related to output current(s) and current setting pins (IDxx and ISET) apply to GroupA and GroupB.

(3)

Symbol

Parameter

Condition

Min

Typ

Max

Units

2.7V

≤ VIN ≤ 5.5V

18.65

21.90

mA

ENA = '1', 53A = 62A = '0'', ENB = ENC = '0'

20.28

(-8%)

(+8%)

(%)

4 LEDs in GroupA

Output Current Regulation

GroupA

2.7V

≤ VIN ≤ 5.5V

18.70

22.10

mA

ENA = '1', 53A = 62A = '1', ENB = ENC = '0'

20.40

(-8.5%)

(+8.5%)

(%)

6 LEDs in GroupA

2.7V

≤ VIN ≤ 5.5V

Output Current Regulation

18.40

21.60

mA

ENB = '1', 53A = 62A = '0', ENA = ENC = '0'

20.00

GroupB

(-8%)

(+8%)

(%)

3 LEDs in GroupB

Output Current Regulation

2.7V

≤ VIN ≤ 5.5V

18.20

21.20

mA

IDxx

19.70

IDC

ENC = '1', ENA = ENB = '0'

(-7.5%)

(+7.5%)

(%)

Maximum Diode Current per Dxx

RSET = 8.33kΩ

30

mA

Output(4)

22.5

DxA

Output Current Regulation

3.2V

≤ VIN ≤ 5.5V

22.5

GroupA, GroupB, and GroupC Enabled

VLED = 3.6V

mA

DxB

(4)

RSET = 10.5kΩ

22.5

DxC

GroupA (4 LEDs)

0.4

1.8

IDxx-

LED Current Matching(5)

2.7V

≤ VIN ≤ 5.5V

GroupA (6 LEDs)

1.0

2.7

%

MATCH

GroupB (3 LEDs)

0.7

2.5

VDxx 1x to 3/2x Gain Transition

VDxTH

VDxA and/or VDxB Falling

150

mV

Threshold

Current sink Headroom Voltage

IDxx = 95% ×IDxx (nom.)

VHR

Requirement

65

mV

(IDxx (nom) ≈ 20mA)

(6)

Gain = 3/2

2.4

Open-Loop Charge Pump Output

ROUT

Ω

Resistance

Gain = 1

0.9

IQ

Quiescent Supply Current

Gain = 1.5x, No Load

2.1

2.5

mA

ISD

Shutdown Supply Current

All ENx bits = "0"

3.7

5.5

µA

VSET

ISET Pin Voltage

2.7V

≤ VIN ≤ 5.5V

1.25

V

IDxA-B-C /

Output Current to Current Set Ratio

189

ISET

GroupA, GroupB, GroupC

fSW

Switching Frequency

1.0

1.3

1.6

MHz

tSTART

Start-up Time

VOUT = 90% steady state

250

µs

Reset

0

0.580

VHWEN

HWEN Voltage Thresholds

2.7V

≤ VIN ≤ 5.5V

V

Normal Operation

1.075

VIN

I2C Compatible Interface Voltage Specifications (SCL, SDIO)

(3)

CIN, CVOUT, C1, and C2 : Low-ESR Surface-Mount Ceramic Capacitors (MLCCs) used in setting electrical characteristics

(4)

The maximum total output current for the LM2756 should be limited to 180mA. The total output current can be split among any of the

three Groups (IDxA = IDxB = IDxC = 30mA Max.). Under maximum output current conditions, special attention must be given to input

voltage and LED forward voltage to ensure proper current regulation. See the Maximum Output Current section of the datasheet for

more information.

(5)

For the two groups of current sinks on a part (GroupA and GroupB), the following are determined: the maximum sink current in the

group (MAX), the minimum sink current in the group (MIN), and the average sink current of the group (AVG). For each group, 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 for the Group. The matching figure for a given part is considered to be the highest matching figure of the two Groups.

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

(6)

For each Dxxpin, headroom voltage is the voltage across the internal current sink connected to that pin. For Group A, B, and C current

sinks, VHRx = VOUT -VLED. If headroom voltage requirement is not met, LED current regulation will be compromised.

4

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