HT7L4091
Symbol
Tdelay
Description
Delay from CS trip to GDR
Linear Dimming pin voltage range
Blanking interval
Test Condition
Min.
—
Typ. Max. Unit
VCS=VCS_TH+50mV
110
—
—
VCS_TH
400
18.1
0.3
—
ns
V
VLD
—
—
0
Tblank
200
14.7
—
300
16.4
—
ns
μs
V
T
off
Off time
R =410k
W
T
VOL
GATE Output Low Level
GATE Output High Level
Gate output rise time
VINDC=17V, Io=-20mA
VOH
VINDC=17V, Io=20mA
12
—
V
Trise
CGATE=500pF
—
120
50
—
ns
ns
—
—
%
ms
V
Tfall
Gate output fall time
CGATE=500pF
—
—
TOTP
∆TOTP
∆fJitter
TJP
Thermal shutdown temperature
Thermal shutdown temperature hysteresis
Switch frequency jitter ratio
Jitter Period
—
—
140
25
—
—
—
—
—
fsw = 60kHz
—
—
±4
—
—
4
—
VCS-short
Short circuit protection Voltage
0.45
0.5
0.55
Note 3: Specifications are production tested at TA=room temperature. Specifications over the -40°C to 85°C
operating temperature range are assured by design, characterization and correlation with Statistical Quality
Controls (SQC).
LEDꢀgateꢀdrivingꢀcircuitryꢀwillꢀbeꢀturnedꢀon.ꢀWhileꢀ
Functional Description
theꢀvoltageꢀonꢀtheꢀCSꢀpinꢀisꢀlargerꢀthanꢀtheꢀinternalꢀ
TheꢀHT7L4091ꢀisꢀaꢀuniversalꢀAC/DCꢀconstantꢀcurrentꢀ
referenceꢀvoltage,ꢀtheꢀLEDꢀgateꢀdrivingꢀcircuitryꢀ
LEDꢀdriverꢀdesignedꢀforꢀpeakꢀcurrentꢀmodeꢀcontrol.ꢀ
willꢀbeꢀturnedꢀoffꢀforꢀaꢀconstantꢀToffꢀtime.ꢀAfterꢀtheꢀ
TheꢀdeviceꢀprovidesꢀbothꢀLEDꢀLinearꢀandꢀPWMꢀ
Toffꢀtime,ꢀtheꢀgateꢀdrivingꢀcircuitryꢀwillꢀbeꢀturnꢀonꢀ
dimmingꢀcurrentꢀfunctions.ꢀTheꢀhighꢀinputꢀvoltageꢀ
ifꢀtheꢀvoltageꢀonꢀtheꢀCSꢀpinꢀisꢀlessꢀthanꢀtheꢀinternalꢀ
fromꢀaꢀrectifiedꢀ85Vꢀtoꢀ260VꢀACꢀpowerꢀisꢀclampedꢀ
referenceꢀvoltage.ꢀGoodꢀlineꢀregulationꢀisꢀaꢀfeatureꢀ
toꢀunderꢀ25Vꢀbyꢀanꢀexternalꢀcircuitꢀandꢀanꢀinternalꢀ
ofꢀconstantꢀoff-timeꢀoperationꢀandꢀtheꢀLEDꢀcurrentꢀisꢀ
Zenerꢀdiode.ꢀTheꢀdeviceꢀalsoꢀcontainsꢀanꢀinputꢀUnder-
independentꢀofꢀtheꢀinputꢀvoltage.ꢀSinceꢀtheꢀinductorꢀ
Voltage-Lockoutꢀ(UVLO)ꢀcircuit.ꢀWhenꢀtheꢀvoltageꢀ
currentꢀrippleꢀisꢀdependentꢀonꢀtheꢀLEDꢀstringꢀvoltage,ꢀ
suppliedꢀonꢀtheꢀVINꢀpinꢀexceedsꢀtheꢀUVLOꢀhighꢀ
theꢀLEDꢀstringꢀvoltageꢀvariationꢀwillꢀresultꢀinꢀLEDꢀ
threshold,ꢀtheꢀgateꢀdriverꢀisꢀenabled.ꢀIfꢀtheꢀinputꢀ
currentꢀvariation.ꢀThisꢀisꢀtypicallyꢀnotꢀaꢀproblemꢀsinceꢀ
voltageꢀfallsꢀbelowꢀtheꢀUVLOꢀlowꢀthreshold,ꢀtheꢀgateꢀ
theꢀLEDꢀvoltageꢀvariationꢀforꢀaꢀgivenꢀloadꢀisꢀfairlyꢀ
driverꢀisꢀturnedꢀoff.
small.
RCSꢀcanꢀbeꢀcalculatedꢀusingꢀtheꢀfollowingꢀequation:
LED Current Control
0.25
0.25
Theꢀ HT7L4091ꢀ deviceꢀ isꢀ aꢀ constantꢀ off-timeꢀ
peakꢀcurrentꢀmodeꢀcontroller.ꢀWithꢀreferenceꢀtoꢀ
theꢀApplicationꢀCircuit,ꢀtheꢀLEDꢀpeakꢀcurrentꢀisꢀ
programmedꢀbyꢀanꢀexternalꢀcurrentꢀsenseꢀresistorꢀ(RCS)ꢀ
connectedꢀbetweenꢀtheꢀCSꢀandꢀtheꢀgroundꢀpins.ꢀTheꢀ
CSꢀpinꢀisꢀconnectedꢀtoꢀaꢀnon-invertingꢀterminalꢀofꢀ
anꢀinternalꢀcomparatorꢀofꢀwhichꢀanꢀinternalꢀ250mVꢀ
referenceꢀisꢀtiedꢀtoꢀtheꢀinvertingꢀterminal.ꢀTheꢀLEDꢀ
peakꢀcurrentꢀthroughꢀtheꢀRCSꢀresistorꢀwillꢀgenerateꢀ
aꢀvoltageꢀwhichꢀisꢀappliedꢀonꢀtheꢀcomparatorꢀnon-
invertingꢀterminalꢀandꢀcompareꢀwithꢀtheꢀinternalꢀ
250mVꢀreferenceꢀvoltage.ꢀIfꢀtheꢀvoltageꢀonꢀtheꢀCSꢀpinꢀ
isꢀlessꢀthanꢀtheꢀinternalꢀreferenceꢀvoltageꢀ250mV,ꢀtheꢀ
RCS
=
=
I
peak
(1+1/ 2× Ripple) ⋅ ILED
WhereꢀIpeakꢀisꢀtheꢀMaximumꢀLEDꢀCurrent,ꢀRippleꢀ
isꢀtheꢀPeakꢀtoꢀPeakꢀLEDꢀCurrent,ꢀandꢀILEDꢀisꢀtheꢀ
AverageꢀLEDꢀCurrent.ꢀRippleꢀcanꢀbeꢀcontrolledꢀbyꢀ
theꢀinductor.ꢀ0
Toff ×V
out
ILED × Ripple = IRipple
=
L
Referꢀ toꢀ “Inductorꢀ Design”ꢀ forꢀ theꢀ inductorꢀ
calculation.ꢀReferꢀtoꢀ“ProgrammableꢀOffꢀTime”ꢀforꢀ
Toffꢀcalculation.
Rev. 1.20
4
March 12, 2013
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