HV9918K7-G [MICROCHIP]
LED DISPLAY DRIVER, DSO8;
| 型号： | HV9918K7-G |
| 厂家： | 
MICROCHIP |
| 描述： | LED DISPLAY DRIVER, DSO8 驱动 接口集成电路 |
| 文件： | 总7页 (文件大小：434K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Supertex inc.
HV9918
Hysteretic, Buck, High Brightness LED Driver
with High-Side Current Sensing
Features
General Description
► Hysteretic control with high-side current sensing
The HV9918 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
up to 700mA. The device is well suited for applications requiring
a wide input voltage range. The high-side current sensing and an
integrated current-setting circuitry minimize the number of external
components while delivering an accurate average output.
► Integrated 40V 1.0Ω MOSFET
► >90% Efficiency
► Wide input voltage range: 4.5 to 40V
► ±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
Dedicated pulse-width modulation (PWM) input enables pulsed
LED dimming over a wide range of brightness levels. A hysteretic
control method ensures excellent input supply rejection and fast
response during load transients and PWM dimming.
► -40ºC to +125ºC operating temperature range
Applications
The HV9918 offers an analog-controlled PWM dimming feature
that reduces the output current by applying an external DC voltage
below the internal 2.0V threshold voltage fromADIM to GND.ADIM
can also accept input from a resistor divider including a negative
temperature coefficient (NTC) thermistor connected between
ADIM and GND, or a positive temperature coefficient (PTC)
thermistor connected between ADIM and VDD thus providing a
PWM thermal-foldback feature that reduces the LED current when
the temperature of the LED string exceeds a specified temperature
point. Additional features include thermal-shutdown protection.
► Low voltage industrial and architectural lighting
► General purpose constant current source
► Signage and decorative LED lighting
► Indicator and emergency lighting
The high switching frequency up to 2.0MHz permits the use of
small inductors and capacitors, minimizing space and cost in the
overall system.
The HV9918 comes in a small 8-Lead DFN package and is ideal
for industrial and general lighting applications.
Typical Application Circuit
RSENSE
L
CIN
VIN
CS
SW
RAMP
ADIM
DIM
0 - 2.0V
VDD
GND
HV9918
Supertex inc. ● 1235 Bordeaux Drive, Sunnyvale, CA 94089 ● Tel: 408-222-8888 ● www.supertex.com
HV9918
Pin Description
Ordering Information
Package Options
8
7
CS
1
2
SW
8-Lead DFN
3.00x3.00mm body,
0.80mm height (max),
0.65mm pitch
Device
VIN
GND
GND
HV9918
HV9918K7-G
VDD
DIM
RAMP
ADIM
3
4
6
5
-G indicates package is RoHS compliant (‘Green’)
8-Lead DFN (K7)
(top view)
Product Marking
Y = Last Digit of Year Sealed
W = Code for Week Sealed
L = Lot Number
9 9 1 8
Absolute Maximum Ratings
Parameter
YW LL
Value
-0.3 to +45V
-0.3 to +6.0V
-1.0 to +0.3V
1.6W
= “Green” Packaging
VIN, CS, SW to GND
8-Lead DFN (K7)
VDD, RAMP, DIM, ADIM to GND
CS to VIN
Thermal Resistance
Package
Continuous power dissipation, (TA = +25°C)
Operating temperature range
Junction temperature
θja
-40°C to +125°C
+150°C
8-Lead DFN (K7)
60OC/W
Mounted on FR-4 board, 25mm x 25mm x 1.57mm
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.
Electrical Characteristics
(VIN = 12V, VDIM = VDD, VRAMP = GND, CVDD = 1.0µF, RCS = 0.5Ω, TA = TJ = -40OC to +125OC* unless otherwise noted)
Sym
VIN
Description
Min
Typ
Max
40
5.5
1.5
900
-
Units Conditions
Input DC supply voltage range
Internally regulated voltage
Supply current
4.5
-
-
-
-
V
V
DC input voltage
VDD
4.5
VIN = 6.0 to 40V
SW = GND
IIN
-
-
-
-
-
-
-
mA
µA
IIN, SDN
Shutdown supply current
DIM< 0.7V
30
VIN = 4.5V, VDD = 0V
VIN = 4.5V, VDD = 4.0V
IIN, LIM
Current limit
mA
8.0
-
fSW
Switchingr frequency
-
-
2.0
4.5
-
MHz ---
UVLO
ΔUVLO
VDD Undervoltage lockout threshold
V
VDD rising
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.
Supertex inc. ● 1235 Bordeaux Drive, Sunnyvale, CA 94089 ● Tel: 408-222-8888 ● www.supertex.com
2
HV9918
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
VRS(HI)
VRS(LO)
Sense voltage threshold high
213
158
-
-
246
182
mV
mV
(VIN - VCS) rising
(VIN - VCS) falling
Rising edge of
(VIN - VCS) = VRS(HI) +70mV to
VSW = 0.9 • VIN
Sense voltage threshold low
Propagation delay to SW off
tDPDL
-
-
70
-
-
ns
ns
Falling edge of
(VIN - VCS) = VRS(LO) -70mV to
VSW = 0.1 • VIN
tDPDH
Propagation delay to SW on
70
ICS
Current-sense input current
-
-
-
1.0
70
µA
(VIN - VCS) = 200mV
---
ICS(HYS)
Current-sense threshold hysteresis
56
mV
DIM Input
VIH
Pin DIM input high voltage
Pin DIM input low voltage
2.2
-
-
-
-
V
V
---
---
VIL
tON
0.7
DIM rising edge to
VSW = 0.9 • VIN
Turn-on time
Turn-off time
-
-
100
100
-
-
ns
ns
DIM falling edge to
VSW = 0.1 • VIN
tOFF
Output Switch
IDC
SW continuous current
-
-
-
-
0.7
2.0
-
A
Ω
---
RON
ILEAK
ON resistance
1.0
10
---
SW leakage current
µA
VIN = 40V
Over-Temperature Protection
TOT
Over temperature trip limit
128
-
140
60
-
-
ºC
ºC
---
---
∆THYST
Temperature hysteresis
Analog Control of PWM Dimming
130
550
-
-
300
1250
-
CRAMP = 47nF
fRAMP
Dimming frequency
Hz
-
0.1
-
CRAMP = 10nF
VLOW
VHiGH
VOS
RAMP threshold, Low
RAMP threshold, High
ADIM offset voltage
V
V
---
---
---
1.8
-35
2.1
35
-
mV
*
Guaranteed by design and characterization, 100% tested at TA = 25OC. Typical characteristics are given at TA = 25OC.
Supertex inc. ● 1235 Bordeaux Drive, Sunnyvale, CA 94089 ● Tel: 408-222-8888 ● www.supertex.com
3
HV9918
Block Diagram
REGULATOR
VIN
VDD
SW
+
-
CS
CURRENT
SENSE
COMPARATOR
BANDGAP
REF
+
-
DIM
UVLO
COMPARATOR
GND
PWM RAMP
0.1~1.9V
RAMP
ADIM
-
+
HV9918
Application Information
General Description
DIM Input
The HV9918 allows dimming with a PWM signal at the DIM
input. A logic level below 0.7V at DIM halts SW switching,
turning the LED current off. To turn the LED current back on,
the logic level at DIM must be at least 2.2V.
The HV9918 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 includes an internal 40V
1.0Ω 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. PWM
dimming can also be achieved by applying a DC voltage be-
tween 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 ex-
ternal components while delivering LED current with ±5%
accuracy using a 1% sense resistor.
ADIM and RAMP Inputs
The PWM dimming scheme can be also implemented by
applying an analog control signal to ADIM pin. If an ana-
log control 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.
1
fPWM
=
CRAMP • 120kΩ
Undervoltage Lockout (UVLO)
DIM and ADIM inputs can be used simultaneously. In such
case, fPWM(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 SW signal.
The HV9918 includes a 3.7V under-voltage lockout (UVLO)
with 500mV hysteresis. When VIN falls below 3.7V, switching
of SW is disabled. Switching of SW resumes once VIN is 4.5V
or higher.
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.
5.0V Regulator
VDD is the output of a 5.0V regulator capable of sourcing
8mA. Bypass VDD to GND with a 1.0μF capacitor.
Supertex inc. ● 1235 Bordeaux Drive, Sunnyvale, CA 94089 ● Tel: 408-222-8888 ● www.supertex.com
4
HV9918
One possible application of the ADIM feature of the HV9918 the inductor ramps up and the voltage across the sense re-
may include protection of the LED load from over-tempera- sistor reaches the upper threshold, the internal MOSFET at
ture by connecting an NTC thermistor at ADIM, as shown in SW turns off. The MOSFET turns on again when the inductor
Figure 1.
current ramps down through the freewheeling diode until the
voltage across the sense resistor equals the lower threshold.
Use the following equation to determine the inductor value
for a desired value of operating frequency fS:
VDD
HV9918
(VIN - VOUT )VOUT (VIN - VOUT )tDPDL VOUT tDPDH
ADIM
L =
-
-
fSVIN ∆IO
∆IO
∆IO
NTC
GND
where:
VRS(HI) - VRS(LO)
Figure 1
∆IO =
RSENSE
Setting LED Current with External Resistor RSENSE
The output current in the LED is determined by the external and tDPDL, tDPDH are the propagation delays. Note, that the cur-
current sense resistor (RSENSE) connected between VIN and rent ripple ∆I in the inductor L is greater than ∆IO. This ripple
CS. Disregarding the effect of the propagation delays, the can be calculated from the following equation:
sense resistor can be calculated as:
(VIN - VOUT)tDPDL
VOUT tDPDH
∆I =∆IO +
+
(VRS(HI) + VRS(LO)
)
1
200mV
ILED
L
L
RSENSE
≈
•
=
2
ILED
For the purpose of the proper inductor selection, note that
the maximum switching frequency occurs at the highest VIN
and VOUT = VIN/2.
Selecting Buck Inductor L
The HV9918 regulates the LED output current using an input
comparator with hysteresis (Figure 2). As the current through
1
fS
TS =
tDPDL
ILED
VRS(HI)
RSENSE
VRS(LO)
RSENSE
tDPDH
ΔIO
ΔI
t
t
VDIM
Figure 2
Supertex inc. ● 1235 Bordeaux Drive, Sunnyvale, CA 94089 ● Tel: 408-222-8888 ● www.supertex.com
5
HV9918
PCB Layout Guidelines
Thermal Shutdown
Careful PCB layout is critical to achieve low switching losses
and stable operation. Use a multilayer board whenever pos-
sible for better noise immunity. Minimize ground noise by
connecting high-current ground returns, the input bypass
capacitor ground lead, and the output filter ground lead to
a single point (star ground configuration). The fast di/dt loop
is formed by the input capacitor CIN, the free-wheeling diode
and the HV9918 switching MOSFET. To minimize noise inter-
action, this loop area should be as small as possible. Place
RSENSE as close as possible to the input filter and VIN. For
better noise immunity, a Kelvin connection is strongly recom-
mended between CS and RSENSE. Connect the exposed tab
of the IC to a large-area ground plane for improved power
dissipation.
The HV9918 thermal-shutdown feature turns off the SW driv-
er when the junction temperature exceeds +140°C. The SW
driver turns back on when the junction temperature drops
60°C below the shutdown temperature threshold.
Freewheeling Diode Selection
The forward voltage of the freewheeling diode should be
as low as possible for better efficiency. A Schottky diode
is a good choice as long as the breakdown voltage is high
enough to withstand the maximum operating voltage. The
forward current rating of the diode must be at least equal to
the maximum LED current.
LED Current Ripple
The LED current ripple is equal to the inductor current ripple.
In cases when a lower LED current ripple is needed, a ca-
pacitor can be placed across the LED terminals.
Pin Description
Pin #
Pin
Description
1
2
CS
Current sense input. Senses LED string current.
Input voltage 4.5 to 40V DC.
VIN
3
RAMP
ADIM
DIM
Analog PWM dimming ramp output.
4
Analog 0 ~ 2.0V signal input for analog control of PWM dimming.
PWM signal input.
5
6
VDD
GND
SW
Internally regulated supply voltage. Connect a capacitor from VDD to ground.
Device ground.
7
8
Open Drain Output of an internal 40V 1.0Ω MOSFET.
Must be wired to pin 7 on PCB.
TAB
GND
Supertex inc. ● 1235 Bordeaux Drive, Sunnyvale, CA 94089 ● Tel: 408-222-8888 ● www.supertex.com
6
HV9918
8-Lead DFN Package Outline (K7)
3.00x3.00mm body, 0.80mm height (max), 0.65mm pitch
D2
D
8
8
E
E2
Note 1
(Index Area
D/2 x E/2)
Note 1
(Index Area
D/2 x E/2)
1
1
View B
Top View
Bottom View
Note 3
θ
A
L
Seating
Plane
A3
L1
b
e
Note 2
A1
Side View
View B
Notes:
1. A Pin 1 identifier must be located in the index area indicated. The Pin 1 identifier can be: a molded mark/identifier; an embedded metal marker; or
a printed indicator.
2. Depending on the method of manufacturing, a maximum of 0.15mm pullback (L1) may be present.
3. The inner tip of the lead may be either rounded or square.
Symbol
A
A1
A3
b
D
D2
1.60
-
E
E2
1.35
-
e
L
L1
0.00*
-
θ
0O
-
MIN
0.70
0.00
0.02
0.05
0.25
0.30
0.35
2.85*
3.00
3.15*
2.85*
3.00
3.15*
0.30
0.40
0.50
Dimension
(mm)
0.20
REF
0.65
BSC
NOM 0.75
MAX 0.80
2.50
1.75
0.15
14O
JEDEC Registration MO-229, Variation WEEC-2, Issue C, Aug. 2003.
* This dimension is not specified in the JEDEC drawing.
Drawings not to scale.
Supertex Doc. #: DSPD-8DFNK73X3P065, Version C081109.
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline
information go to http://www.supertex.com/packaging.html.)
Supertex inc. does not recommend the use of its products in life support applications, and will not knowingly sell them for use in such applications unless it receives
an adequate “product liability indemnification insurance agreement.” Supertex inc. does not assume responsibility for use of devices described, and limits its liability
to the replacement of the devices determined defective due to workmanship. No responsibility is assumed for possible omissions and inaccuracies. Circuitry and
specifications are subject to change without notice. For the latest product specifications refer to the Supertex inc. (website: http//www.supertex.com)
©2010 Supertex inc. All rights reserved. Unauthorized use or reproduction is prohibited.
Supertex inc.
1235 Bordeaux Drive, Sunnyvale, CA 94089
Tel: 408-222-8888
www.supertex.com
Doc.# DSFP-HV9918
C092710
7
相关型号：
HV9919K7-G
LED Driver, 1-Segment, PDSO8, 3 X 3 MM, 0.80 MM HEIGHT, 0.65 MM PITCH, GREEN, MO-229WEEC-2, DFN-8
SUPERTEX
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