HV9918K7-G Supertex, HV9918K7-G Datasheet - Page 4

• Manufacturer Part Number: HV9918K7-G
• Description: LED Drivers Hysteretic Buck High Brightness LED Driv
• Manufacturer: Supertex

Specifications of HV9918K7-G

• Operating Supply Voltage: 4.5 V to 40 V
• Maximum Supply Current: 1.5 mA
• Maximum Power Dissipation: 1.6 W
• Maximum Operating Temperature: + 125 C
• Mounting Style: SMD/SMT
• Package / Case: DFN-8
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Block Diagram
Application Information
General Description
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.
Undervoltage Lockout (UVLO)
The HV9918 includes a 3.7V under-voltage lockout (UVLO)
with 500mV hysteresis. When V
of SW is disabled. Switching of SW resumes once V
or higher.
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.
RAMP
ADIM
VIN
CS
IN
BANDGAP
falls below 3.7V, switching
●
PWM RAMP
REF
0.1~1.9V
1235 Bordeaux Drive, Sunnyvale, CA 94089
COMPARATOR
COMPARATOR
IN
REGULATOR
CURRENT
UVLO
is 4.5V
+
SENSE
+
-
-
+
-
4
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.
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.
DIM and ADIM inputs can be used simultaneously. In such
case, f
the dimming signal at DIM. The smaller dimming duty cycle
of ADIM and DIM will determine the SW 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.
PWM(MAX)
f
PWM
●
=
Tel: [phone]
must be selected lower than the frequency of
C
RAMP
HV9918
1
• 120kΩ
●
www.supertex.com
VDD
GND
SW
DIM
HV9918