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A8435 Datasheet(PDF) 4 Page - Allegro MicroSystems

Part No. A8435
Description  High Efficiency Charge Pump White LED Driver
Download  9 Pages
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Maker  ALLEGRO [Allegro MicroSystems]
Homepage  http://www.allegromicro.com
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A8435 Datasheet(HTML) 4 Page - Allegro MicroSystems

   
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High Efficiency Charge Pump White LED Driver
A8435
4
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
ELECTRICAL CHARACTERISTICS1
VIN = VEN1 = VEN2 = 3.6 V, C1 = C2 = 1 μF, TA = –40 to 85°C, typical values at TA = 25°C (unless otherwise noted)
Characteristics
Symbol
Test Conditions
Min.
Typ.
Max.
Units
Input Voltage Range
VIN
2.7
5.5
V
Undervoltage Lockout Threshold
VUVLO
VIN falling, VUVLOHYS= 35 mV
2.25
2.45
2.60
V
UVLO Hysteresis Window
VUVLOHYS
35
mV
Quiescent Current
IQ
Switching, TA = 25°C
2.8
4
mA
EN1 = EN2 = GND, TA = 25°C
0.1
1
μA
Soft-Start Completion Time
tSS
2
ms
ISET Bias Voltage
VISETBIAS
0.56
0.6
0.64
V
ISET Leakage in Shutdown
VISETLKG
0.01
1
μA
ISET Current Range
IISET
40
140
μA
ISET to LEDx Current Ratio
ILEDx/IISET
IISET = 60 μA,
CTRL = open or HIGH
EN1 = EN2 = VIN
190
219
245
A/A
EN1 = VIN, EN2 = GND
105
121
137
A/A
EN1 = GND, EN2 = VIN
51
60
69
A/A
IISET = 60 μA,
CTRL = LOW
Full brightness
200
A/A
ILED Accuracy
EILED
EN1 = EN2 = VIN, RSET = 4.3 kΩ
±0.9
%
LED Current Matching2
ΔILED
VIN =3.6 V, ILED = 30 mA per LED
±0.5
%
Regulation Voltage at LEDx (1.5×)
VLED
EN1 = EN2 = VIN
150
mV
Open Loop Output Resistance3
ROUT
1× mode: [(VIN – VOUT)/IOUT]
1.1
Ω
1.5× mode: [(1.5 × VIN – VOUT)/IOUT]
3.6
Ω
1× to 1.5× Mode Transition Voltage at LEDx
VTrans
VLEDx Falling
100
mV
Transition to Dropout Voltage Difference4
ΔVdr
Measured as VTrans – VDropout
60
mV
LED Leakage in Shutdown
VLEDLKG EN1 = EN2 = GND, VIN = 5.5 V, TA = 25°C
0.01
1
μA
Oscillator Frequency
fosc
1
MHz
Output Overvoltage Protection5
VOVP
Open circuit at any LED that is programmed to be
in the ON state
5.74
V
CTRL, EN1, EN2 Input High Logic Threshold6
VIH
1.6
V
CTRL, EN1, EN2 Input Low Logic Threshold6
VIL
0.4
V
Input High Current
IIH
VIH = VIN
––
1
μA
Input Low Current
IIL
VIL = GND
1
μA
EN1 Pulse Low Time7
tLO
0.5
500
μs
EN1 Pulse High Time7
tHI
0.5
μs
Initial EN1 Pulse High Time7
tHI(Init)
First EN1 pulse after shutdown
100
μs
Shutdown Delay7
tSHDN
Falling edge of EN1 pulse
2
3
ms
Thermal-Shutdown Threshold
TSHDN
20°C hysteresis
165
°C
1Specifications guaranteed by design over operating temperature range, –40°C to 85°C.
2LED current matching is defined as (ILEDX – ILED(AVG))/ILED(AVG).
3The Open Loop Output Resistance for 1.5× mode is measured with one of the LEDx pins tied to ground or open (thus its voltage is always less
than 80 mV).
4Dropout Voltage, VDropout, is defined as the LEDx-to-GND voltage at which ILEDx drops 10% below the value of ILEDX at VLEDX = 200 mV.
5Guaranteed by design.
6EN2 is not used when CTRL is tied to ground.
7Applies only when CTRL is tied to ground. See figure 3 in Application Information section.


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