Document
Supertex inc.
AT9919
Hysteretic, Buck, High Brightness LED Driver with High-Side Current Sensing
Features
►► Hysteretic control with high-side current sensing ►► Wide input voltage range: 4.5 to 40V ►► >90% Efficiency ►► Typical ±5% LED current accuracy ►► Up to 2.0MHz switching frequency ►► Adjustable constant LED current ►► Analog or PWM control signal for PWM dimming ►► Over-temperature protection ►► -40ºC to +125ºC operating temperature range ►► AEC-Q100 compliant
Applications
►► Automotive LED lighting applications
General Description
The AT9919 is a PWM controller IC designed to drive high brightness LEDs using a buck topology. It operates from an input voltage of 4.5 to 40VDC and employs hysteretic control with a high-side current sense resistor to set the constant output current.
The operating frequency range can be set by selecting the proper inductor. Operation at high switching frequency is possible since the hysteretic control maintains accuracy even at high frequencies. This permits the use of small inductors and capacitors minimizing space and cost in the overall system.
LED brightness control is achieved with PWM dimming from an analog or PWM input signal. Unique PWM circuitry allows true constant color with a high dimming range. The dimming frequency is programmed using a single external capacitor.
The AT9919 comes in a small, 8-Lead DFN package and is qualified for automotive LED lighting applications.
Typical Application Circuit
CIN
RSENSE
L
0 - 2.0V
Doc.# DSFP-AT9919 A061212
CS VIN
RAMP
VDD
ADIM
GATE
DIM GND
AT9919
Supertex inc. www.supertex.com
AT9919
Ordering Information
Part Number
Package
AT9919K7-G
8-Lead DFN
-G indicates package is RoHS compliant (‘Green’)
Packing 3000/Reel
Pin Description
CS 1 VIN 2 RAMP 3
GND
8 GATE 7 GND 6 VDD
ADIM 4
5 DIM
Absolute Maximum Ratings
Parameter
VIN, CS to GND
Value -0.3 to +45V
8-Lead DFN (K7)
(top view)
Product Marking
VDD, GATE, RAMP, DIM, ADIM to GND CS to VIN Continuous power dissipation, (TA = +25°C) Operating temperature range Junction temperature
-0.3 to +6.0V -1.0 to +0.3V
1.6W -40°C to +125°C
+150°C
9919 YWLL
Y = Last Digit of Year Sealed W = Code for Week Sealed L = Lot Number
= “Green” Packaging
8-Lead DFN (K7)
Storage temperature range
-65°C to +150°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
Typical Thermal Resistance
Package
θja
8-Lead DFN
37OC/W
Mounted on FR-4 board, 25mm x 25mm x 1.57mm
Electrical Characteristics
(VIN = 12V, VDIM = VDD, VRAMP = GND, CVDD = 1.0µF, RCS = 0.5Ω, TA = TJ = -40OC to +125OC* unless otherwise noted)
Sym Description
Min Typ
Max Units Conditions
VIN Input DC supply voltage range
4.5 - 40 V DC input voltage
VDD Internally regulated voltage
4.5 - 5.5 V VIN = 6.0 to 40V
IIN Supply current
- - 1.5 mA GATE open
IIN, SDN
Shutdown supply current
- - 900 µA DIM < 0.7V
IIN, LIM
Current limit
- 30 - mA VIN = 4.5V, VDD = 0V
- 8.0 -
VIN = 4.5V, VDD = 4.0V
fOSC Oscillator frequency
- - 2.0 MHz ---
UVLO VDD Undervoltage lockout threshold
-
- 4.5 V VDD rising
ΔUVLO VDD Undervoltage lockout hysteresis
-
500 - mV VDD falling
* Guaranteed by design and characterization, 100% tested at TA = 25OC. Typical characteristics are given at TA = 25OC.
Doc.# DSFP-AT9919 A061212
Supertex inc.
2 www.supertex.com
AT9919
Electrical Characteristics
(VIN = 12V, VDIM = VDD, VRAMP = GND, CVDD = 1.0µF, RCS = 0.5Ω, TA = TJ = -40OC to +125OC* unless otherwise noted)
Sym Description
Min Typ
Max Units Conditions
Sense Comparator
VCS(HI) VCS(LO) VCS(AVG)
tDPDH
Sense voltage threshold high Sense voltage threshold low Average reference voltage
Propagation delay to output high
198 230 257 mV (VIN - VCS) rising
147 170 195 mV (VIN - VCS) falling
186
200
214
mV VCS(AVG) = 0.5VCS(HI) + 0.5VCS(LO)
-
70
-
ns
Falling edge of (VIN - VCS) = VRS(LO) - 70mV
tDPDL Propagation delay to output low
ICS Current-sense input current VCS(HYS) Current-sense threshold hysteresis
DIM Input
-
-
70
-
ns
Rising edge of (VIN - VCS) = VRS(HI) + 70mV
- 1.0 µA (VIN - VCS) = 200mV
56 80 mV ---
VIH Pin DIM input high voltage VIL Pin DIM input low voltage
tON Turn-on time
2.2 -
- V ---
- - 0.7 V ---
-
100
-
ns
DIM rising edge to VGATE = 0.5 x VDD, CGATE = 2.0nF
tOFF Turn-off time
-
100
-
ns
DIM falling edge to VGATE = 0.5 x VDD, CGATE =2.0nF
Gate Driver
GATE current, source†
IGATE
GATE current, sink†
TRISE
GATE output rise time
TFALL
GATE output fall time
VGATE(HI) GATE high output voltage
VGATE(LO) GATE low output voltage
Over-Temperature Protection
TOT Over temperature trip limit†
∆THYST Temperature hysteresi.