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PDF HV9911 Data sheet ( Hoja de datos )
| Número de pieza | HV9911 | |
| Descripción | Switch-Mode LED Driver IC | |
| Fabricantes | Supertex | |
| Logotipo |  |
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HV9911
Switch-Mode LED Driver IC
with High Current Accuracy
Features
► Switch mode controller for single switch drivers
♦ Buck
♦ Boost
♦ Buck-boost
♦ SEPIC
► Works with high side current sensing
► Closed loop control of output current
► High PWM dimming ratio
► Internal 250V linear regulator (can be extended
using external Zener diodes)
► Internal 2% voltage reference (0°C < TA < 85°C)
► Constant frequency or constant off-time operation
► Programmable slope compensation
► Enable & PWM dimming
► +0.2A/-0.4A GATE drive
► Output short circuit protection
► Output over voltage protection
► Synchronization capability
► Programmable MOSFET current limit
Applications
► RGB backlight applications
► Battery powered LED lamps
► Other DC/DC LED drivers
General Description
The HV9911 is a current mode control LED driver IC designed
to control single switch PWM converters (buck, boost, buck-
boost, or SEPIC), in a constant frequency or constant off-time
mode. The controller uses a peak current control scheme,
(with programmable slope compensation), and includes
an internal transconductance amplifier to control the output
current in closed loop, enabling high output current accuracy.
In the constant frequency mode, multiple HV9911s can be
synchronized to each other, or to an external clock, using
the SYNC pin. Programmable MOSFET current limit enables
current limiting during input under voltage and output overload
conditions. The IC also includes a 0.2A source and 0.4A sink
GATE driver for high power applications. An internal 9.0 -
250V linear regulator powers the IC, eliminating the need for
a separate power supply for the IC. HV9911 provides a TTL
compatible, PWM dimming input that can accept an external
control signal with a duty ratio of 0-100% and a frequency of
up to a few kilohertz. The IC also provides a FAULT output
which, can be used to disconnect the LEDs in case of a fault
condition, using an external disconnect FET.
The HV9911 based LED driver is ideal for RGB backlight
applications with DC inputs. The HV9911 based LED lamp
drivers can achieve efficiency in excess of 90% for buck and
boost applications.
Typical Application Circuit - Boost
CIN
CDD
RSLOPE
CREF
RT
L1 Q1
1 VIN
2 VDD
4 GND
GATE 3
CS 5
OVP 12
RSC
SC
6 SC
7 RT
FAULT 11
HV9911
FDBK 16
10 REF
COMP 14
CC
RL2
9 CLIM
RL1
RR1
15 IREF
RR2
PWMD 13
SYNC 8
D1
ROVP1
CO
RCS
ROVP2
Q2
RS
● 1235 Bordeaux Drive, Sunnyvale, CA 94089 ● Tel: 408-222-8888 ● www.supertex.com
1 page  
HV9911
Electrical Characteristics (cont.)
(The specifications are at TA = 25°C and VIN = 24V, unless otherwise noted.)
Sym Parameter
Min Typ Max Units Conditions
Oscillator
fOSC1
Oscillator frequency
fOSC2
DMAX
Oscillator frequency
Maximum duty cycle
IOUTSYNC Sync output current
IINSYNC Sync input current
Output Short Circuit
TOFF
Propagation time for short circuit
detection
TRISE,FAULT Fault output rise time
TFALL,FAULT Fault output fall time
GFAULT Amplifier gain at IREF pin
Slope Compensation
*-
*-
--
--
--
88
308
-
-
0
100 112
350 392
90 -
10 20
- 200
kHz RT = 909kΩ
kHz RT = 261kΩ
% ---
µA ---
µA VSYNC < 0.1V
--
--
--
--
-
-
-
1.8
- 250 ns IREF = 200mV; FDBK = 450mV;
FAULT goes from high to low
- 300 ns 1.0nF capacitor at FAULT pin
- 200 ns 1.0nF capacitor at FAULT pin
2 2.2
IREF = 200mV
ISLOPE Current sourced out of SC pin
--
0
- 100 µA ---
GSLOPE Internal current mirror ratio
- - 1.8 2 2.2
- ISLOPE = 50µA; RCSENSE = 1.0kΩ
Notes:
* Denotes the specifications which apply over the full operating ambient temperature range of -40°C < TA < +85°C.
Functional Block Diagram
Linear
VIN Regulator
VDD
CLIM
CS
DIS
Blanking
100ns
1:2 ramp
_
+
+
_
SC
FDBK
IREF
COMP
_ Gm
+
13R
R
DIS
2
POR
Vbg
REF
GATE
RQ
FAULT
S
+
_
Q R POR
Q
DIS
S
VBG
OVP
SYNC
One Shot
RT
PWMD
GND
● 1235 Bordeaux Drive, Sunnyvale, CA 94089 ● Tel: 408-222-8888 ● www.supertex.com
5
5 Page 
HV9911
PWM Dimming
PWM dimming can be achieved by driving the PWMD pin
with a TTL compatible source. The PWM signal is connected
internally to the three different nodes – the transconductance
amplifier, the FAULT output, and the GATE output.
When the PWMD signal is high, the GATE and FAULT pins
are enabled, and the output of the transconductance opamp
is connected to the external compensation network. Thus,
the internal amplifier controls the output current. When the
PWMD signal goes low, the output of the transconductance
amplifier is disconnected from the compensation network.
Thus, the integrating capacitor maintains the voltage across
it. The GATE is disabled, so the converter stops switching
and the FAULT pin goes low, turning off the disconnect
switch.
The output capacitor of the converter determines the
PWM dimming response of the converter, since it has to
get charged and discharged whenever the PWMD signal
goes high or low. In the case of a buck converter, since the
inductor current is continuous, a very small capacitor is used
across the LEDs. This minimizes the effect of the capacitor
on the PWM dimming response of the converter. However,
in the case of a boost converter, the output current is
discontinuous, and a very large output capacitor is required
to reduce the ripple in the LED current. Thus, this capacitor
will have a significant impact on the PWM dimming response.
By turning off the disconnect switch when PWMD goes low,
the output capacitor is prevented from being discharged,
and thus the PWM dimming response of the boost converter
improves dramatically.
Note:
Disconnecting the capacitor might cause a sudden spike
in the capacitor voltage as the energy in the inductor is
dumped into the capacitor. This might trigger the OVP
comparator if the OVP point is set too close to the maximum
operating voltage. Thus, either the capacitor has to sized
slightly larger or the OVP set point has to be increased.
Note:
The HV9911 IC might latch-up if the PWMD pin is pulled
0.3V below GND, causing failure of the part. This abnor-
mal condition can happen if there is a long cable between
the PWM signal and the PWMD pin of the IC. It is recom-
mended that a 1.0kΩ resistor be connected between the
PWMD pin and the PWM signal input to the HV9911. This
resistor, when placed close to the IC, will damp out any
ringing that might cause the voltage at the PWMD pin to
go below GND.
Avoiding False Shutdowns of the HV9911
The HV9911 has two fault modes which trigger a latched
protection mode, an over current (or short circuit) protection,
and an over voltage protection.
To prevent false triggering due to the tripping of the over
voltage comparator, (due to noise in the GND traces on
the PCB), it is recommended that a 1.0 - 10nF capacitor
be connected between the OVP pin and GND. Although
this capacitor will slow down the response of the over
voltage protection circuitry somewhat, it will not affect the
overall performance of the converter, as the large output
capacitance in the boost design will limit the rate of rise of
the output voltage.
In some cases, the over current protection may be triggered
during PWM dimming, when the FAULT goes high and the
disconnect switch is turned on. This triggering of the over
current protection is related to the parasitic capacitance of
the LED string (shown as a lumped capacitance CLED in Fig.
4).
During normal PWM dimming operation, the HV9911
maintains the voltage across the output capacitor (CO), by
turning off the disconnect switch and preserving the charge
in the output capacitance when the PWM dimming signal
is low. At the same time, the voltage at the drain of the
disconnect FET is some non-zero value VD. When the PWM
dimming signal goes high, FET Q2 is turned ON. This causes
the voltage at the drain of the FET (VD) to instantly go to
zero. Assuming a constant output voltage VO,
iSENSE = CLED • d(VO - VD) / dt
= -CLED • dVD / dt
In this case, the rate of fall of the drain voltage of the
disconnect FET is a large value (since the FET turns on very
quickly) and this causes a spike of current through the sense
resistor, which could trigger the over current protection
(depending on the parasitic capacitance of the LED string).
To prevent this condition, a simple RC low pass filter network
can be added as shown in Fig. 5. Typical values are RF =
1.0kΩ and CF = 470pF. This filter will block the FDBK pin from
seeing the turn-on spike and normalize the PWM dimming
operation of the HV9911 boost converter. This will have
minimal effect on the stability of the loop but will increase
the response time to an output short. If the increase in the
response time is large, it might damage the output current
sense resistor due to exceeding its peak-current rating.
● 1235 Bordeaux Drive, Sunnyvale, CA 94089 ● Tel: 408-222-8888 ● www.supertex.com
11
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet HV9911.PDF ] | |
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