Supertex inc.
LED Driver with Average-Mode,
Constant Current Control
Features
►
►
►
►
►
►
Fast average current control
Programmable constant off-time switching
PWM / linear dimming input
Output short circuit protection with skip mode
Ambient operating temperature -40
O
C to +125
O
C
Pin-compatible with the HV9910B and HV9961
HV9861A
General Description
The HV9861A is a patented, average-mode, constant current control
LED driver IC operating in a constant off-time mode. Unlike the
HV9910B, this control IC does not produce a peak-to-average error,
and therefore greatly improves the accuracy, line and load regulation
of the LED current without any need for loop compensation or high-
side current sensing. The output LED current accuracy is ±3%.
The IC is equipped with a current limit comparator for hiccup-mode
output short circuit protection. Internal over-temperature protection
is provided. The internally regulated voltage (V
DD
) for the HV9861A
is 7.5V.
The IC can be powered from a 12 - 450V supply. A PWM dimming
input is provided that accepts an external control TTL-compatible
signal. The output current can be programmed by an internal 270mV
reference, or controlled externally through a 0 - 1.5V dimming input.
The IC is pin-to-pin compatible with the Supertex HV9910B and
HV9961, and can be used as a drop-in replacement for many
applications to improve the LED current accuracy and regulation.
Applications
►
►
►
►
►
►
DC/DC or AC/DC LED driver applications
LED backlight driver for LCD displays
General purpose constant current source
LED signage and displays
Architectural and decorative LED lighting
LED street lighting
Typical Application Circuit
12 to
450VDC
LED
Load
1
VIN
5 PWMD
GATE 4
HV9861A
6 VDD
7 LD
GND
3
CS 2
RT 8
RT
RCS
Sets
LED
Current
Supertex inc.
1235 Bordeaux Drive, Sunnyvale, CA 94089
Tel: 408-222-8888
www.supertex.com
HV9861A
Ordering Information
Package Options
Device
4.90x3.90mm body
1.75mm height (max)
1.27mm pitch
Pin Description
VIN
1
NC
2
NC
3
VIN
1
CS
2
GND
3
GATE
4
8
RT
7
LD
6
VDD
5
PWMD
16
NC
15
NC
14
RT
13
LD
12
VDD
11
NC
10
NC
9
8-Lead SOIC
9.90x3.90mm body
1.75mm height (max)
1.27mm pitch
16-Lead SOIC
CS
4
GND
5
NC
6
NC
7
GATE
8
HV9861A
HV9861ALG-G
HV9861ANG-G
-G indicates package is RoHS compliant (‘Green’)
PWMD
8-Lead SOIC (LG)
(top view)
16-Lead SOIC (NG)
(top view)
Product Marking
Absolute Maximum Ratings
Parameter
V
IN
to GND
V
DD
to GND
CS, LD, PWMD, GATE, RT to GND
Junction temperature range
Storage temperature range
Continuous power dissipation
(T
A
= +25°C)
8-Lead SOIC
16-Lead SOIC
Value
-0.5V to +470V
12V
-0.3V to (V
DD
+0.3V)
-40°C to +150°C
-65°C to +150°C
650mW
1000mW
9861A
YWW
LLLL
Y = Last Digit of Year Sealed
WW = Week Sealed
L = Lot Number
= “Green” Packaging
Package may or may not include the following marks: Si or
8-Lead SOIC (LG)
Top Marking
YWW
HV9861ANG
LLLLLLLL
Bottom Marking
CCCCCCCCC AAA
Y = Last Digit of Year Sealed
WW = Week Sealed
L = Lot Number
C = Country of Origin*
A = Assembler ID*
= “Green” Packaging
*May be part of top marking
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.
Package may or may not include the following marks: Si or
16-Lead SOIC (NG)
Thermal Resistance
Package
8-Lead SOIC
16-Lead SOIC
θ
JA
128
O
C/W
82
O
C/W
Electrical Characteristics
(Specifications are at T
Sym
Description
Input DC supply voltage range
1
Shut-down mode supply current
*
*
A
= 25°C. V
IN
= 12V, V
LD
= V
DD
, PWMD = V
DD
unless otherwise noted))
Min
12
-
Typ
-
0.5
Max
450
1
Unit
V
mA
Conditions
DC input voltage
Pin PWMD to GND
Input
V
INDC
I
INSD
Notes:
1. Also limited by package power dissipation limit, whichever is lower.
*
Denotes the specifications which apply over the full operating ambient temperature range of -40°C < T
A
< +125°C.
Supertex inc.
1235 Bordeaux Drive, Sunnyvale, CA 94089
2
Tel: 408-222-8888
www.supertex.com
HV9861A
Electrical Characteristics
(Specifications are at T
Sym
V
DD
ΔV
DD, line
ΔV
DD, load
UVLO
∆UVLO
∆V
DD(UV)
I
IN,MAX
Description
Internally regulated voltage
Line regulation of V
DD
Load regulation of V
DD
V
DD
undervoltage lockout
threshold
V
DD
undervoltage lockout
hysteresis
V
DD
voltage margin
Maximum input current
(limited by UVLO)
-
-
-
*
-
*
#
#
*
*
-
A
= 25°C. V
IN
= 12V, V
LD
= V
DD
, PWMD = V
DD
unless otherwise noted))
Min
7.25
-
-
6.45
-
500
3.5
1.5
-
2.2
8.5
Typ
7.50
-
-
-
500
-
-
-
-
-
-
Max
7.75
1
100
-
-
-
-
-
0.8
-
13.5
Unit
V
V
mV
V
mV
mV
mA
Conditions
500pF at GATE; R
T
= 226kΩ
V
IN
= 12 - 450V,
500pF at GATE; R
T
= 226kΩ
I
DD(ext)
= 0 - 1mA,
500pF at GATE; R
T
= 226kΩ
V
IN
rising
V
IN
falling
∆V
DD(UV)
= V
DD
- UVLO
V
IN
= 12V, T
A
= 25
O
C
V
IN
= 12V, T
A
= 125
O
C
V
IN
= 12 - 450V
V
IN
= 12 - 450V
V
PWMD
= 0.8V
---
---
Offset = V
CS
- (A
V(LD)
• V
LD
);
V
LD
= 1.2V
---
V
LD
falling
V
LD
rising
---
CS = V
CS
+ 30mV
Reduction in output LED current
may occur beyond this duty cycle
---
CS = V
CS
+ 30mV
---
CS = V
DD
Internal Regulator
PWM Dimming
V
EN(lo)
V
EN(hi)
I
EN
V
CS
A
V(LD)
A
V
• V
LD(OFFSET)
ΔV
CS(TEMP)
V
LD(OFF)
ΔV
LD(OFF)
T
BLANK
T
ON(min)
D
MAX
V
CS
T
DELAY
T
HICCUP
T
ON(min)
PWMD input low voltage
PWMD input high voltage
Internal pull-down current at
PWMD
Current sense reference voltage
LD-to-CS voltage ratio
LD-to-CS voltage offset
CS threshold temp regulation
LD input voltage, shutdown
LD input voltage, enable
Current sense blanking interval
Minimum on-time
Maximum steady-state duty
cycle
Hiccup threshold voltage
Current limit delay CS-to-GATE
Short circuit hiccup time
Minimum on-time (short circuit)
V
V
μA
Average Current Sense Logic
-
-
-
#
-
-
*
-
*
262
0.175
-10
-
-
-
140
-
80
-
-
-
-
150
200
-
-
-
280
0.182
10
5
-
-
290
760
-
mV
-
mV
mV
mV
mV
ns
ns
%
Short Circuit Protection
*
-
-
-
410
-
500
-
-
-
-
-
500
150
850
430
mV
ns
μs
ns
Notes:
*
Denotes the specifications which apply over the full operating ambient temperature range of -40°C < T
A
< +125°C.
# Guaranteed by design.
Supertex inc.
1235 Bordeaux Drive, Sunnyvale, CA 94089
3
Tel: 408-222-8888
www.supertex.com
HV9861A
Electrical Characteristics
(Specifications are at T
Sym
Description
A
= 25°C. V
IN
= 12V, V
LD
= V
DD
, PWMD = V
DD
unless otherwise noted))
Min
Typ
Max
Unit
Conditions
T
OFF
Timer
T
OFF
Off-time
-
-
-
-
-
-
#
#
32
8
0.165
0.165
-
-
128
-
40
10
-
-
30
30
140
20
48
12
-
-
50
50
-
-
μs
R
T
= 1MΩ
R
T
= 226kΩ
V
GATE
= 0V, V
DD
= 7.5V
V
GATE
= V
DD
, V
DD
= 7.5V
C
GATE
= 500pF, V
DD
= 7.5V
C
GATE
= 500pF, V
DD
= 7.5V
---
---
GATE Driver
I
SOURCE
I
SINK
t
RISE
t
FALL
T
SD
ΔT
SD
Sourcing current
Sinking current
Output rise time
Output fall time
Shut-down temperature
Hysteresis
A
A
ns
ns
O
O
Over-temperature Protection
C
C
Notes:
# Guaranteed by design.
Functional Block Diagram
VIN
+
-
0.15/0.20V
Regulator
UVLO
VDD
+
-
POR
LD
MIN (V
LD
• 0.18, 0.27V)
Auto-REF
GATE
CS
Latch
Enable
Blanking
IN
Average Current
Control Logic
OUT
PWMD
+
-
CLK
R Q
S Q
11µA
GND
0.45V
HV9861A
Supertex inc.
650µs
T
OFF
Timer
i
Current
Mirror
RT
1235 Bordeaux Drive, Sunnyvale, CA 94089
4
Tel: 408-222-8888
www.supertex.com
HV9861A
Application Information
General Description
Peak-current control (as in the HV9910B) of a buck con-
verter is the most economical and simple way to regulate
its output current. However, it suffers accuracy and regula-
tion problems that arise from the so-called peak-to-average
current error, contributed to by the current ripple in the out-
put inductor and the propagation delay in the current sense
comparator. The full inductor current signal is unavailable
for direct sensing at the ground potential in a buck converter
when the control switch is referenced to the same ground
potential because the control switch is only conducting for
small periods. While it is very simple to detect the peak cur-
rent in the switch, controlling the average inductor current
is usually implemented by level translating the sense sig-
nal from +V
IN
. Though this is practical for relatively low input
voltage V
IN
, this type of average-current control may become
excessively complex and expensive in offline AC or other
high-voltage DC applications.
The HV9861A employs Supertex’ patented control scheme,
achieving fast and very accurate control of average current
in the buck inductor through sensing the switch current only.
No compensation of the current control loop is required. The
LED current response to PWMD input is similar to that of the
HV9910B. The inductor current ripple amplitude does not af-
fect this control scheme significantly, and therefore, the LED
current is independent of the variation in inductance, switch-
ing frequency or output voltage. Constant off-time control of
the buck converter is used for stability and to improve the
LED current regulation over a wide range of input voltages.
(Note that, unlike the HV9910B, this IC does not support the
constant-frequency mode of operation.)
feedback operates in a fast open-loop mode. No compensa-
tion is required. Output current is programmed simply as:
I
LED
=
0.27V
R
CS
(2)
When the voltage at the LD input V
LD
≥ 1.5V. Otherwise:
I
LED
=
V
LD
• 0.18
R
CS
(3)
The above equations are only valid for continuous conduc-
tion of the output inductor. It is a good practice to design the
inductor such that the switching ripple current in it is 30~40%
of its average peak-to-peak, full load, DC current. Hence,
the recommended inductance can be calculated as:
L
O
=
V
O(MAX)
• T
OFF
0.4 • I
O
(4)
The duty-cycle range of the current control feedback is lim-
ited to D ≤ 0.8. A reduction in the LED current may occur
when the LED string voltage V
O
is greater than 80% of the
input voltage V
IN
of the HV9861A LED driver.
Reducing the output LED voltage V
O
below V
O(MIN)
= V
IN
•
D
MIN
, where D
MIN
= 760ns/(T
OFF
+760ns), may also result
in the loss of regulation of the LED current. This condition,
however, causes an increase in the LED current and can
potentially trip the short-circuit protection comparator.
The typical output characteristic of the HV9861A LED driver
is shown in Fig.1. The corresponding HV9910B characteris-
tic is given for comparison.
0.60
0.55
OFF Timer
LED Current (A)
The timing resistor connected to RT determines the off-time
of the gate driver, and it must be wired to GND. (Wiring this
resistor to GATE as with the HV9910B is no longer support-
ed.) The equation governing the off-time of the GATE output
is given by:
T
OFF
(µs) =
R
T
(kΩ)
25
+ 0.3
(1)
Output Characteristics
V
IN
= 170VDC
0.50
0.45
0.40
0.35
0.30
0.25
0
10
20
30
40
Within the range of 30kΩ ≤ R
T
≤ 1.0MΩ.
HV9861A
Average Current Control Feedback and Output
Short Circuit Protection
The current through the switching MOSFET source is aver-
aged and used to give constant-current feedback. This cur-
rent is detected using a sense resistor at the CS pin. The
HV9910B
50
60
Output Voltage (V)
Fig.1. Typical output characteristic of an HV9861A LED
driver.
Supertex inc.
1235 Bordeaux Drive, Sunnyvale, CA 94089
5
Tel: 408-222-8888
www.supertex.com
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