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PDF HV9967B Data sheet ( Hoja de datos )
| Número de pieza | HV9967B | |
| Descripción | Integrated LED Driver | |
| Fabricantes | Supertex | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de HV9967B (archivo pdf) en la parte inferior de esta página. Total 7 Páginas | ||
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Supertex inc.
Integrated LED Driver
with Average-Mode Current Control
HV9967B
Features
►► 3% accurate LED current
►► Integrated 60V, 0.8Ω MOSFET
►► Low sensitivity to external component variation
►► Single resistor LED current setting
►► Fixed off-time control
►► PWM dimming input
►► Output short circuit protection with skip mode
►► Over-temperature protection
►► Available in compact 8-Lead MSOP and 8-Lead
DFN packages
Applications
►► DC/DC or AC/DC LED drivers
►► RGB backlighting drivers for flat panel displays
►► General purpose constant current source
►► Signage and decorative LED lighting
►► Chargers
General Description
The HV9967B is an average-mode current control LED driver IC
operating in a constant off-time mode.
The IC features an integrated 60V, 0.8Ω MOSFET that can be
used as a stand-alone buck converter switch, or connected as a
source driver for driving an external high-voltage depletion-mode
MOSFET. The HV9967B is powered through its switching output
when the integrated switch is off. Hence, the same external
MOSFET can be used as a high-voltage linear regulator for
powering the IC.
The LED current is programmed with one external resistor. The
average-mode current control method does not produce a peak-
to-average error, and therefore greatly improves current accuracy
and line and load regulation of the LED current without any need
for loop compensation or direct sensing of the LED current at a
high-voltage potential. The auto-zero circuit cancels the effects of
the input offset voltage and of the propagation delay of the current
sense comparator.
Typical Application Circuit
8.0 - 60VDC
+
CIN
RSENSE
U1
4
PWMD
1
SW
HV9967B
2
RSENSE
8
VDD
PGND AGND RT
37 6
RT
D1 CO
L1
CDD
Doc.# DSFP-HV9967B
B060712
LED
String
Supertex inc.
www.supertex.com
1 page  
HV9967B
Reducing the output LED voltage VO below VO(MIN) = VIN • DMIN,
where DMIN = 0.8µs/(TOFF + 0.8µs), may also result in the loss
of regulation of the LED current. This condition, however,
causes increase in the LED current and can potentially trip
the short-circuit protection comparator threshold.
SW Input and Linear Regulator
HV9967B includes an integrated 60V, 0.8Ω switching
MOSFET at the SW input. The power for the IC is supplied
from a linear 5.0V regulator that is also derived from the SW
input.
The short circuit protection comparator trips when the volt-
age at RSENSE exceeds 0.4V. When this occurs, the SW
off-time THICCUP = 800µs is generated to prevent stair-casing
of the inductor current and potentially its saturation due to
insufficient output voltage. The typical short-circuit current is
shown in the waveform of Fig. 1.
0.44V/RSENSE
800µs
PWM Dimming
The HV9967B features a TTL compatible dimming input
PWMD. Applying a square-wave voltage to PWMD will mod-
ulate the duty ratio of the LED current accordingly. The rising
and falling edges are limited by the current slew rate in the
inductor. The first switching cycle is terminated upon reach-
ing the 250mV level at RSENSE. The circuit will reach the
steady state within 3~4 switching cycles regardless of the
switching frequency.
Fig.1. Short-circuit inductor current.
A leading-edge blanking delay is provided at RSENSE to
prevent false triggering of the current feedback and the short
circuit protection.
Over-Temperature Protection
The HV9967B includes over-temperature protection. Typi-
cally, when the junction temperature exceeds 145OC, switch-
ing of the SW input is disabled. The switching resumes when
the temperature falls by approximately 20OC from the trip
point.
Pin Description
Pin #
Function Description
1 SW Drain of 60V 0.8Ω NDMOS switch and input of H/V regulator.
2
RSENSE
Source of NDMOS switch and current sense input.
Connect a resistor to GND to program the output current and short circuit thresholds.
3 PGND Power ground. Must be wired to AGND on PCB.
4 PWMD PWM dimming input. This TTL input enables switching of SW when in high state.
5 NC No connection.
6 RT Resistor connected between RT and VDD programs the off-time of SW.
7 AGND Analog ground (0V).
8
VDD
Power supply for all internal circuits. Bypass with a low ESR capacitor to PGND (>0.5μF).
Connect GATE of external depletion-mode NFET for high-voltage operation.
Doc.# DSFP-HV9967B
B060712
Supertex inc.
5 www.supertex.com
5 Page | ||
| Páginas | Total 7 Páginas | |
| PDF Descargar | [ Datasheet HV9967B.PDF ] | |
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