HV9957K7-G Supertex, HV9957K7-G Datasheet - Page 7

• Manufacturer Part Number: HV9957K7-G
• Description: LED Lighting Drivers LED DRIVER 6 CHANNEL W/ FAULT PROTECTION
• Manufacturer: Supertex

Specifications of HV9957K7-G

• Product Category: LED Lighting Drivers
• Rohs: yes
• Input Voltage: 5 V
• Maximum Supply Current: 10 mA
• Maximum Operating Temperature: + 125 C
• Mounting Style: SMD/SMT
• Package / Case: QFN-24
• Minimum Operating Temperature: - 40 C
• Factory Pack Quantity: 3000

Application Information
Operation
The HV9957 combines a switch-mode boost converter and
six low-dropout linear current regulators to provide the ad-
vantages of high efficiency and precise current control.
Supplies
Two independent supplies may be used to power the back-
light controller circuit: one to supply the HV9957 (V
another to supply the boost converter (V
the boost converter may range from 2.7 to 28V depending
on the load. The HV9957 supply (V
The boost converter need not be supplied from the same
source as for the HV9957. The low ON-resistance internal
boost converter switch combined with CCM operation allows
boost converter supply voltages as low as 2.7V for single-
cell lithium-ion batteries. At lower boost supply voltages, out-
put power decreases due to the increased switch current.
The HV9957 has two power states - shutdown and active.
To keep standby currents low, internal circuits are powered
down when shut down.
The active state is when the HV9957 is driving the LED
strings. When transitioning from shutdown to active, a soft-
start circuit ramps input current over a 6.4ms interval.
HV9957 States
Under-voltage Lock Out (UVLO)
The boost converter and output drivers will not be enabled
until V
the UVLO hysteresis voltage from the turn-ON threshold, the
boost converter and output drivers are disabled.
Boost Converter
The boost converter provides the high voltage needed to
drive the LED strings. It gets its feedback from the active
output channels, maintaining a minimum voltage of 900mV
across the linear current regulators (CH1 - 6). Therefore, the
boost converters’ output voltage (V
DD
1-0-1 for <10µs
0 for >50µs
reaches its UVLO thresholds. When V
EN pin
0 → 1
Supertex inc.
1
DD
BST
) is 5.0V nominal.
1235 Bordeaux Drive, Sunnyvale, CA 94089
) will be 900mV (V
Reset fault
Shutdown
Soft-start
IN
Active
State
). The supply for
DD
falls by
DD
) and
DO
)
7
plus the maximum LED string voltage drop (V
It is recommended that the boost ratio (V
to 9 or less.
Due to boost switch limitations, load capability decreases
with lower supply voltages. As with any switching converter,
input power is relatively constant for a given load. Since P
V
The following graph depicts the load capability for various
supply voltages and LEDs/string.
Load Capability
Based on mathematical modeling and assumed character-
istics of external components. The actual circuit may yield
different results.
I
should be factored in, depending on the inductor value and
boost frequency
V
The boost converter frequency is pin-programmable in four
steps by applying the appropriate voltage to the FBST pin.
IN
Cells
IN
OUT
Batt
is based on assumed 90% efficiency and CCM. Ripple
1
2
3
• I
is based on 3.2V LEDs.
IN
1/3V
2/3V
, input current increases as input voltage decreases.
FBST
V
V
0V
LED /
BST
DD
str
12
17
7
DD
DD
= V
Tel: [phone]
DO
22.4
38.4
54.4
V
(V)
+ V
OUT
STR(MAX)
Internal
375kHz
500kHz
500kHz
1.0MHz
11.4
12.6
2.7
3.8
4.2
5.4
7.6
8.4
8.1
V
(V)
Osc
IN
www.supertex.com
P
Max
3.4
4.0
4.0
6.9
6.9
6.9
9.8
9.8
9.8
(W)
LOAD
BST
/ V
Max
(mA)
I
STR(MAX)
25
30
30
30
30
30
30
30
30
OUT
LED
XTAL
HV9957
Osc
÷64
÷48
÷32
÷24
) be limited
).
Avg
1.4
1.0
1.1
1.4
1.0
0.9
1.3
1.0
0.9
(A)
I
IN
IN
=