SP7686AER-L Exar Corporation, SP7686AER-L Datasheet - Page 12

• 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

APPLICATIONS INFORMATION
CONT’D
The SP7686 charge pump circuit requires 3
capacitors: 10μF input, 2.2μF output and
0.22μF
recommended. For the input capacitor, a value
of 10μF will help reduce input voltage ripple
for applications sensitive to ripple on the
battery voltage. All the capacitors should be
surface mount ceramic for low lead inductance
necessary at the 2.4MHz switching frequency
of the SP7686 and to obtain low ESR, which
improves bypassing on the input and output
and improves output voltage drive by reducing
output resistance. Ceramic capacitors with
X5R
recommended
selection
included in Table 1 below.
The input and output capacitors should be
located as close to the V
possible to obtain best bypassing, and the
returns should be connected directly to the
PGND pin or to the thermal pad ground
located under the SP7686. The fly capacitor
should be located as close to the C1 and C2
pins as possible. See the RECOMMENDED
LAYOUT
recommended layout.
To obtain low output ripple, a value of 2.2μF is
recommended for C
the value for C
For best regulation and low input current
ripple the input capacitor value of 10μF is
recommended.
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fly
section
of
X7R
FLY
recommended
for
A smaller 4.7μF for Cin will
capacitor
of 0.22μF is recommended.
temperature
OUT
for
most
. For all output currents
GRM188R60J106ME19D
GRM155R60J224KE19D
GRM155R60J105KE19D
GRM188R60J225KE19D
GRM188R60J475KE19D
IN
C1608X5R0J107M
C1005X5R0J224K
C1005X5R0J105K
C1608X5R0J225K
C1608X5R0J475K
details
Part Number
and V
applications.
are
capacitors
C
C
o
o
grade
OUT
n
n
s
on
s
Table 1: Capacitor Selection
typically
t
t
pins as
a
a
n
n
t
t
are
the
is
C
C
A
Capacitance/
12/16
u
u
r
r
0.22uF/6.3V
0.22uF/6.3V
Voltage
r
2.2uF/6.3V
4.7uF/6.3V
2.2uF/6.3V
4.7uF/6.3V
r
10uF/6.3V
10uF/6.3V
e
e
1uF/6.3V
1uF/6.3V
work but input voltage ripple will increase and
may effect regulation.
R
and Flash modes so the sense resistor R
determined by the value needed in the Torch
or Flash mode for the desired output current
by the equation:
R
R
Once the R
one mode, the I
other mode using the following equation:
I
Using an example of Torch current of 180mA
and Flash current of 450mA, calculated R
for Torch is 0.06 /0.180 = 0.333 Ohms. Use a
standard value of 0.33 Ohms. I
mode is 0.16/0.33 = 480mA
The power obtained in the Flash mode would
be:
P
The typical 0603 surface mount resistor is
rated 1/10 Watt continuous power and 1/5
Watt pulsed power, more than enough for this
application. For other applications, the P
power can be calculated and resistor size
selected. The R
to be size 0603 for most applications. The
range of typical resistor values and sizes are
shown here in Table 2.
n
n
The 7686A part has fixed FB voltages in Torch
OUT
FLASH
SENSE
SENSE
ESISTOR
t
t
F
F
= V
l
l
=V
=V
= V
a
a
s
s
FB
FB
FB
h
h
FB
/I
/I
/ R
Size/Type/Thickness
S
SENSE
D
D
OUT
OUT
*I
0402/X5R/0.55mm
0402/X5R/0.55mm
0402/X5R/0.55mm
0402/X5R/0.55mm
ELECTION FOR THE
0603/X5R/0.9mm
0603/X5R/0.9mm
0603/X5R/0.9mm
0603/X5R/0.8mm
0603/X5R/0.8mm
0603/X5R/0.9mm
SENSE
r
r
OUT
i
i
where V
where V
v
v
Capacitor
SENSE
resistor has been selected for
e
e
= 160mV*480mA ~ 77mW.
OUT
r
r
S
S
i
i
P
P
n
resistor is recommended
n
can be selected for the
7
7
FB
FB
D
D
6
=60mV (Torch Mode)
=160mV(Flash Mode)
6
F
F
8
8
N
N
6
6
2
2
/
/
m
m
SP7686A
S
S
OUT
m
m
P
P
100kHz
ESR at
7
7
Rev. 2.1.0
x
for Flash
x
0.05
0.03
0.03
0.02
0.02
0.05
0.03
0.03
0.02
0.02
6
6
3
3
SENSE
8
8
m
m
SENSE
6
FLASH
6
m
m
A
A
is