HV9967 Supertex, Inc., HV9967 Datasheet - Page 5

• Manufacturer Part Number: HV9967
• Description: Integrated Led Driver With Average-mode Current Control
• Manufacturer: Supertex, Inc.

Reducing the output LED voltage V
D
in the loss of regulation of the LED current. This condition,
however, causes increase in the LED current and can poten-
tially trip the short-circuit protection comparator threshold.
The short circuit protection comparator trips when the volt-
age at RSENSE exceeds 0.41V. When this occurs, the SW
off-time T
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.
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.
Alternative Typical Application (low-voltage DC input)
MIN
, where D
0.44V/R
HICCUP
SENSE
R
Supertex inc.
SENSE
MIN
= 800µs is generated to prevent stair-casing
= 0.8µs / (T
800µs
4
2
8.0 - 60VDC
U1
PWMD
RSENSE
OFF
PGND
+ 0.8µs), may also result
●
3
HV9967
O
1235 Bordeaux Drive, Sunnyvale, CA 94089
below V
AGND
7
O(MIN)
RT
6
VDD
SW
= V
IN
R
C
1
8
•
T
IN
5
SW Output and Linear Regulator
The HV9967 includes an integrated 60V 0.8Ω switching
MOSFET at the SW output, that could be used as a stand-
alone switch for low-volt DC input applications, or as a source
driver of an external depletion mode MOSFET (for example,
DN2450 by Supertex). In both cases, the power for the IC
is supplied from a linear 5.0V regulator that is also derived
from the SW input.
PWM Dimming
The HV9967 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 is will further
reach the steady state within 3~4 switching cycles regard-
less of the switching frequency.
Over-Temperature Protection
The HV9967 includes over-temperature protection. Typical-
ly, when the junction temperature exceeds 145
of the SW input is disabled. The switching resumes when the
temperature falls by approximately 20
D1
●
Tel: [phone]
C
DD
L1
C
O
●
www.supertex.com
O
C from the trip point.
LED
String
O
HV9967
C, switching