Supertex inc.
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
HV9919
General Description
The HV9919 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 HV9919 comes in a small, 8-lead DFN package and is
ideal for industrial and general lighting applications.
Applications
►
►
►
►
Low voltage industrial and architectural lighting
General purpose constant current source
Signage and decorative LED lighting
Indicator and emergency lighting
Typical Application Circuit
R
SENSE
L
C
IN
CS
RAMP
ADIM
VIN
VDD
GATE
GND
0 - 2.0V
DIM
HV9919
Supertex inc.
●
1235 Bordeaux Drive, Sunnyvale, CA 94089
●
Tel: 408-222-8888
●
www.supertex.com
HV9919
Ordering Information
Package Options
Device
3.00x3.00mm body,
0.80mm height (max),
0.65mm pitch
Pin Description
8-Lead DFN
CS
VIN
RAMP
ADIM
1
2
8
7
GATE
GND
VDD
DIM
HV9919
-G indicates package is RoHS compliant (‘Green’)
HV9919K7-G
GND
3
4
6
5
8-Lead DFN (K7)
(top view)
Product Marking
Absolute Maximum Ratings
Parameter
VIN, CS to GND
VDD, GATE, RAMP, DIM, ADIM to GND
CS to VIN
Continuous power dissipation,
(T
A
= +25°C)
Operating temperature range
Junction temperature
Storage temperature range
Value
-0.3 to +45V
-0.3 to +6.0V
-1.0 to +0.3V
1.6W
-40°C to +125°C
+150°C
-65°C to +150°C
H919
YWLL
Y = Last Digit of Year Sealed
W = Code for Week Sealed
L = Lot Number
= “Green” Packaging
8-Lead DFN (K7)
Thermal Resistance
Package
8-Lead DFN (K7)
θ
ja
60
O
C/W
Mounted on FR-4 board, 25mm x 25mm x 1.57mm
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.
Electrical Characteristics
Sym
V
IN
V
DD
I
IN
I
IN, SDN
I
IN, LIM
f
OSC
UVLO
ΔUVLO
Description
(V
IN
= 12V, V
DIM
= V
DD
, V
RAMP
= GND, C
VDD
= 1.0µF, R
CS
= 0.5Ω, T
A
= T
J
= -40
O
C to +125
O
C* unless otherwise noted)
Min
4.5
4.5
-
-
-
-
-
-
-
Typ
-
-
-
-
30
8.0
-
-
500
Max
40
5.5
1.5
750
-
-
2.0
4.5
-
Units
V
V
mA
µA
mA
MHz
V
mV
Conditions
DC input voltage
V
IN
= 6.0 to 40V
GATE open
DIM <0.8V
V
IN
= 4.5V, V
DD
= 0V
V
IN
= 4.5V, V
DD
= 4.0V
---
V
DD
rising
V
DD
falling
Input DC supply voltage range
Internally regulated voltage
Supply current
Shutdown supply current
Current limit
Oscillator frequency
V
DD
Undervoltage lockout threshold
V
DD
Undervoltage lockout hysteresis
*
Guaranteed by design and characterization, 100% tested at T
A
= 25
O
C. Typical characteristics are given at T
A
= 25
O
C.
Supertex inc.
●
1235 Bordeaux Drive, Sunnyvale, CA 94089
●
Tel: 408-222-8888
●
www.supertex.com
2
HV9919
Electrical Characteristics
Sym
V
RS(HI)
V
RS(LO)
t
DPDH
t
DPDL
I
CS
I
CS(HYS)
Description
Sense voltage threshold high
Sense voltage threshold low
Propagation delay to output high
Propagation delay to output low
Current-sense input current
Current-sense threshold hysteresis
Pin DIM input high voltage
Pin DIM input low voltage
Turn-on time
Turn-off time
(V
IN
= 12V, V
DIM
= V
DD
, V
RAMP
= GND, C
VDD
= 1.0µF, R
CS
= 0.5Ω, T
A
= T
J
= -40
O
C to +125
O
C* unless otherwise noted)
Min
213
158
-
-
-
-
2.2
-
-
-
Typ
230
170
70
70
-
56
-
-
100
100
Max
246
182
-
-
1.0
70
-
0.7
-
-
Units
mV
mV
ns
ns
µA
mV
V
V
ns
ns
Conditions
(V
IN
- V
CS
) rising
(V
IN
- V
CS
) falling
Falling edge of
(V
IN
- V
CS
) = V
RS(LO)
- 70mV
Rising edge of
(V
IN
- V
CS
) = V
RS(HI)
+ 70mV
(V
IN
- V
CS
) = 200mV
---
---
---
DIM rising edge to
V
GATE
= 0.5 x V
DD
, C
GATE
= 2.0nF
DIM falling edge to
V
GATE
= 0.5 x V
DD
, C
GATE
=2.0nF
C
GATE
= 1.0nF
C
GATE
= 1.0nF
I
GATE
= 10mA
I
GATE
= -10mA
---
---
C
RAMP
= 10nF
C
RAMP
= 1.0nF
---
---
---
Sense Comparator
DIM Input
V
IH
V
IL
t
ON
t
OFF
Gate Driver
T
RISE
T
FALL
V
GATE(HI)
V
GATE(LO)
T
OT
∆T
HYST
GATE output rise time
GATE output fall time
GATE high output voltage
GATE low output voltage
Over temperature trip limit
Temperature hysteresis
-
-
V
DD
-0.5
-
128
-
-
-
-
-
-20
25
25
-
-
140
60
100
1000
0.1
1.9
-
50
50
-
0.5
-
-
-
-
-
-
+20
ns
ns
V
V
ºC
ºC
Over-Temperature Protection
Analog Control of PWM Dimming
f
RAMP
V
LOW
V
HiGH
V
OS
Dimming frequency
RAMP threshold, Low
RAMP threshold, High
ADIM offset voltage
Hz
V
V
mV
*
Guaranteed by design and characterization, 100% tested at T
A
= 25
O
C. Typical characteristics are given at T
A
= 25
O
C.
†
Guaranteed by design and characterization.
Supertex inc.
●
1235 Bordeaux Drive, Sunnyvale, CA 94089
●
Tel: 408-222-8888
●
www.supertex.com
3
HV9919
Block Diagram
VIN
REGULATOR
VDD
CS
+
-
CURRENT
SENSE
COMPARATOR
GATE
DRIVER
GATE
BANDGAP
REF
+
-
UVLO
COMPARATOR
DIM
GND
RAMP
ADIM
PWM RAMP
0.1~1.9V
-
+
HV9919
Application Information
General Description
The HV9919 is a step-down, constant current, high-bright-
ness LED (HB LED) driver. The device operates from a 4.5
to 40V input voltage range and provides the gate drive out-
put to an external N-channel MOSFET. A high-side current
sense resistor sets the output current and a dedicated PWM
dimming input (DIM) allows for a wide range of diming duty
ratios. The PWM dimming could also be achieved by apply-
ing a DC voltage between 0 and 2.0V to the analog dimming
input (ADIM). In this case, the dimming frequency can be
programmed using a single capacitor at the RAMP pin. The
high-side current setting and sensing scheme minimizes the
number of external components while delivering LED cur-
rent with a ±8% accuracy, using a 1% sense resistor.
Undervoltage Lockout (UVLO)
The HV9919 includes a 3.7V under-voltage lockout (UVLO)
with 500mV hysteresis. When V
IN
falls below 3.7V, GATE
goes low, turning off the external n-channel MOSFET. GATE
goes high once V
IN
is 4.2V or higher.
5.0V Regulator
VDD is the output of a 5.0V regulator capable of sourcing
18mA. Bypass VDD to GND with a 1.0μF capacitor.
DIM Input
The HV9919 allows dimming with a PWM signal at the DIM
input. A logic level below 0.8V at DIM forces the GATE
OUTPUT
low, turning off the LED current. To turn the LED current on,
the logic level at DIM must be at least 2.0V.
ADIM and RAMP Inputs
The PWM dimming scheme can be also implemented by ap-
plying an analog control signal to ADIM pin. If an analog con-
trol signal of 0~2.0V is applied to ADIM, the device compares
this analog input to a voltage ramp to pulse-width-modulate
the LED current. Connecting an external capacitor to RAMP
programs the PWM dimming ramp frequency.
f
PWM
=
10
-6
C
RAMP
DIM and ADIM inputs can be used simultaneously. In such
case, f
PWM(MAX)
must be selected lower than the frequency of
the dimming signal at DIM. The smaller dimming duty cycle
of ADIM and DIM will determine the GATE signal.
When the analog control of the PWM dimming feature is not
used, RAMP must be wired to GND, and ADIM should be
connected to VDD.
Supertex inc.
●
1235 Bordeaux Drive, Sunnyvale, CA 94089
●
Tel: 408-222-8888
●
www.supertex.com
4
HV9919
One possible application of the ADIM feature of the HV9919
may include protection of the LED load from over-tempera-
ture by connecting an NTC thermistor at ADIM, as shown in
Figure 1.
VDD
comparator with hysteresis (Figure 2). As the current through
the inductor ramps up and the voltage across the sense re-
sistor reaches the upper threshold, the voltage at GATE goes
low, turning off the external MOSFET. The MOSFET turns on
again when the inductor current ramps down through the
freewheeling diode until the voltage across the sense resis-
tor equals the lower threshold. Use the following equation to
determine the inductor value for a desired value of operating
frequency f
S
:
L=
(V
IN
- V
OUT
)V
OUT
(V
IN
- V
OUT
)t
DPDL
V
OUT
t
DPDH
-
-
f
S
V
IN
∆I
O
∆I
O
∆I
O
HV9919
ADIM
NTC
GND
Figure 1
Setting LED Current with External Resistor R
SENSE
The output current in the LED is determined by the external
current sense resistor (R
SENSE
) connected between VIN and
CS. Disregarding the effect of the propagation delays, the
sense resistor can be calculated as:
1
2
(V
RS(HI)
+ V
RS(LO)
)
I
LED
200mV
I
LED
where:
∆I
O
=
V
RS(HI)
- V
RS(LO)
R
SENSE
and t
DPDL
, t
DPDH
are the propagation delays. Note, that the cur-
rent ripple ∆I in the inductor L is greater than ∆I
O
. This ripple
can be calculated from the following equation:
(V
IN
- V
OUT
)t
DPDL
L
V
OUT
t
DPDH
L
R
SENSE
≈
•
=
∆I = ∆I
O
+
+
Selecting Buck Inductor L
The HV9919 regulates the LED output current using an input
For the purpose of the proper inductor selection, note that
the maximum switching frequency occurs at the highest V
IN
and V
OUT
= V
IN
/2.
1
f
S
R
SENSE
V
RS(LO)
V
RS(HI)
I
LED
t
DPDL
T
S
=
R
SENSE
t
DPDH
Δ
I
Δ
I
O
t
V
DIM
Figure 2
t
Supertex inc.
●
1235 Bordeaux Drive, Sunnyvale, CA 94089
●
Tel: 408-222-8888
●
www.supertex.com
5
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