LM3537

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SNVS634B – JUNE 2011 – REVISED MAY 2013

CHARGE PUMP AND LED DRIVERS ELECTRICAL CHARACTERISTICS

(1) (2)

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

(

−30°C to +85°C). Unless otherwise specified: VIN_A = 3.6V; VHWEN = VIN_A; VDx = 0.4V; GroupA = GroupB = Fullscale Current;

C1 = C2 = CIN_A= COUT= 1.0 µF.

(3)

Symbol

Parameter

Condition

Min

Typ

Max

Units

Output Current Regulation

2.7V

≤ VIN_A ≤ 5.5V

−7.5%

25

+7.5%

mA

GroupA

8 LEDs in GroupA

Output Current Regulation

2.7V

≤ VIN_A ≤ 5.5V

−7.5%

25

+7.5%

mA

GroupB

4 LEDs in GroupB

IDx

3.2V

≤ VIN_A ≤ 5.5V

Output Current Regulation

VLED = 3.6V

22.3

All LED Drivers Enabled

mA

BankA current code = 1111101b, exp dimming

DxA

All LED Drivers on BankA(4)

scale

2.7V

≤ VIN ≤ 5.5V

GroupA (8 LEDs)

0.8

3

IDx-

LED Current Matching(5)

LED Current =

%

MATCH

GroupB (4 LEDs)

0.4

3

Fullscale current

VDxTH

VDx 1x to 3/2x Gain Transition Threshold VDx Falling

135

mV

Current sink Headroom Voltage

IDx = 95% ×IDx (nom.)

VHR

100

mV

Requirement(6)

(IDx (nom) ≈ 20 mA)

Gain = 3/2

2.4

Open-Loop Charge Pump Output

ROUT

Ω

Resistance(7)

Gain = 1

0.5

Gain = 1.5x, No Load. Current through VIN_A

2.9

4.4

pin. Sensor Bias OFF

IQ

Quiescent Supply Current

mA

Gain = 1x, No Load. Current through VIN_A

1.1

2.4

pin. Sensor Bias OFF

HWEN = 1.8V. All registers in factory defaults

ISB

Standby Supply Current

1.2

µA

state. Current through VIN_A pin.

ISD

Shutdown Supply Current

HWEN = 0V. Current through VIN_A pin.

0.2

1.0

µA

fSW

Switching Frequency

1.1

1.3

1.6

MHz

tSTART

Startup Time

See(8)

250

µs

VALS

ALS Reference Voltage

−6%

1.0

+6%

V

RALS register setting = 00010b

−6%

10.1

+6%

RALS

Internal ALS Resistor

k

Ω

RALS register setting = 00100b

−6%

5.0

+6%

(1)

All voltages are with respect to the potential at the GND pins.

(2)

Min and Max limits are specified by design, test, or statistical analysis. Typical numbers are not ensured, but do represent the most

likely norm.

(3)

CIN_X, COUT, CLDOX, CSEN, C1, and C2 : Low-ESR Surface-Mount Ceramic Capacitors (MLCCs) used in setting electrical characteristics.

(4)

The total output current can be split between the two groups (IDx = 25 mA Max). Under maximum output current conditions, special

attention must be given to input voltage and LED forward voltage to ensure proper current regulation. The maximum total output current

for the LM3537 should be limited to 180 mA.

(5)

For the two groups of current sinks on a part (group A and group B), 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 Dxpin, headroom voltage is the voltage across the internal current sink connected to that pin. For group A and B current sinks,

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

(7)

Specified by design.

(8)

Turn-on time is measured from the moment the charge pump is activated until the VOUT crosses 90% of its target value.

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