LM3537_13 Datasheet, PDF (5/33 Pages) Texas Instruments – 8-Channel WLED Driver with Four Integrated LDOs

LM3537
www.ti.com
SNVS634B – JUNE 2011 – REVISED MAY 2013
CHARGE PUMP AND LED DRIVERS ELECTRICAL CHARACTERISTICS⁽¹⁾⁽²⁾
Limits in standard typeface are for T_J = 25°C, and limits in boldface type apply over the operating ambient temperature range
(−30°C to +85°C). Unless otherwise specified: V_{IN_A} = 3.6V; V_HWEN = V_{IN_A}; V_Dx = 0.4V; GroupA = GroupB = Fullscale Current;
C₁ = C₂ = C_{IN_A}= C_OUT= 1.0 µF.⁽³⁾
Symbol
Parameter
Condition
Min Typ
Max
Units
Output Current Regulation
GroupA
2.7V ≤ V_{IN_A} ≤ 5.5V
8 LEDs in GroupA
−7.5% 25
+7.5%
mA
Output Current Regulation
I_Dx
GroupB
Output Current Regulation
All LED Drivers Enabled
All LED Drivers on BankA⁽⁴⁾
2.7V ≤ V_{IN_A} ≤ 5.5V
4 LEDs in GroupB
−7.5% 25
+7.5%
mA
3.2V ≤ V_{IN_A} ≤ 5.5V
V_LED = 3.6V
BankA current code = 1111101b, exp dimming
22.3
DxA
mA
scale
I_Dx-
MATCH
LED Current Matching⁽⁵⁾
2.7V ≤ V_IN ≤ 5.5V
LED Current =
Fullscale current
GroupA (8 LEDs)
GroupB (4 LEDs)
0.8
3
%
0.4
3
V_DxTH
V_HR
R_OUT
V_Dx 1x to 3/2x Gain Transition Threshold
Current sink Headroom Voltage
Requirement ⁽⁶⁾
Open-Loop Charge Pump Output
Resistance ⁽⁷⁾
V_Dx Falling
I_Dx = 95% ×I_Dx (nom.)
(I_Dx (nom) ≈ 20 mA)
Gain = 3/2
Gain = 1
135
mV
100
mV
2.4
Ω
0.5
I_Q
Quiescent Supply Current
Gain = 1.5x, No Load. Current through VIN_A
pin. Sensor Bias OFF
Gain = 1x, No Load. Current through VIN_A
pin. Sensor Bias OFF
2.9
4.4
mA
1.1
2.4
I_SB
Standby Supply Current
HWEN = 1.8V. All registers in factory defaults
state. Current through VIN_A pin.
1.2
µA
I_SD
f_SW
t_START
V_ALS
R_ALS
Shutdown Supply Current
Switching Frequency
Startup Time
ALS Reference Voltage
Internal ALS Resistor
HWEN = 0V. Current through VIN_A pin.
See ⁽⁸⁾
R_ALS register setting = 00010b
R_ALS register setting = 00100b
0.2
1.1
1.3
250
−6% 1.0
−6% 10.1
−6% 5.0
1.0
1.6
+6%
+6%
+6%
µA
MHz
µs
V
kΩ
(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) C_{IN_X}, C_OUT, C_LDOX, C_SEN, 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,
V_HRx = V_OUT -V_LED. 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 V_OUT crosses 90% of its target value.
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