SP7686AER-L Exar Corporation, SP7686AER-L Datasheet - Page 13

• Manufacturer Part Number: SP7686AER-L
• Description: LED Drivers Driver in 2x3 DFN
• Manufacturer: Exar Corporation
• Series: -r

Specifications of SP7686AER-L

• High Level Output Current: 500 mA
• Operating Supply Voltage: 2.7 V to 5.5 V
• Maximum Supply Current: 3 mA
• Maximum Power Dissipation: Internally Limited
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Package / Case: DFN-8
• Minimum Operating Temperature: - 40 C
• Constant Current: Yes
• Constant Voltage: -
• Topology: PWM, Step-Down (Buck), Step-Up (Boost), Switched Capacitor (Charge Pump)
• Number Of Outputs: 1
• Internal Driver: -
• Type - Primary: Flash/Torch, General Purpose
• Type - Secondary: High Brightness LED (HBLED), White LED
• Frequency: 2MHz ~ 2.8MHz
• Voltage - Supply: 2.7 V ~ 5.5 V
• Voltage - Output: -
• Mounting Type: Surface Mount
• Operating Temperature: -40°C ~ 85°C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

R
The SP7686 part uses an internal 5 bit DAC to
set the LED current. The DAC input is at the
CTRL pin. The user inputs a pulse train of up
to 1MHz to set the LED current. The DAC sets
the feedback voltage point from 58mV to
350mV in 9.7mV steps. The LED current is
determined by the equation:
I
The curves below show the feedback and LED
currents for the CTRL pin pulse count and
standard R
After the desired count is reached the CTRL
input must remain high to hold the count. If
© 2010 Exar Corporation
LED
ESISTOR
= V
FB
/R
SENSE
S
SENSE
ELECTION FOR
Part Reference
resistor values.
RSENSE
RSENSE
RSENSE
RSENSE
RSENSE
RSENSE
RSENSE
SP7686
C
C
0.22ohms
0.27ohms
0.33ohms
0.39ohms
0.47ohms
0.56ohms
0.68ohms
o
o
Value
n
n
s
s
Table 2: Resistor Selection
t
t
a
a
n
n
t
t
C
C
13/16
u
u
Tolerance
1% or 5%
1% or 5%
1% or 5%
1% or 5%
1% or 5%
1% or 5%
1% or 5%
r
r
r
r
e
e
n
n
the CTRL pin goes low for more than 200μs
the part will shutdown. See the timing
diagrams
Characteristics. The first pulse turns on the
SP7686. The first pulse needs to occur at
least 600μsec after V
activate after the power on reset (POR). The
second pulse resets the DAC to 0. The timing
between the first and second pulse needs to
be 25μsec typical to as long as 75μsec. After
the
remains at ground. The third pulse sets the
feedback voltage to 58mV. Subsequent pulses
set the feedback voltage in 9.7mV steps as
shown previously in the Typical Performance
Characteristics.
t
t
F
F
l
l
a
second
a
s
s
h
h
0603
0603
0603
0603
0603
0603
0603
Size
D
D
in
r
r
i
i
pulse
v
v
e
e
the
Panasonic or Vishay
Panasonic or Vishay
Panasonic or Vishay
Panasonic or Vishay
Panasonic or Vishay
Panasonic or Vishay
Panasonic or Vishay
r
r
S
S
Manufacturers
i
i
P
P
n
n
IN
the
7
7
D
D
Typical
6
6
is applied in order to
F
F
8
8
N
N
feedback
6
6
2
2
/
/
m
m
S
S
m
Performance
m
P
P
7
7
Rev. 2.1.0
x
x
6
6
voltage
3
3
8
8
m
m
6
6
m
m
A
A