LTC3783EDHD#TRPBF Linear Technology, LTC3783EDHD#TRPBF Datasheet - Page 13

• Manufacturer Part Number: LTC3783EDHD#TRPBF
• Description: IC LED DRIVER PWM CONTROL 16-DFN
• Manufacturer: Linear Technology
• Type: PWM Controlr

Specifications of LTC3783EDHD#TRPBF

• Constant Current: Yes
• Constant Voltage: Yes
• Topology: Flyback, PWM, SEPIC, Step-Down (Buck), Step-Up (Boost)
• Number Of Outputs: 1
• Internal Driver: No
• Type - Primary: Automotive, General Purpose
• Frequency: 20kHz ~ 1MHz
• Voltage - Supply: 3 V ~ 36 V
• Mounting Type: Surface Mount
• Package / Case: 16-DFN
• Operating Temperature: -40°C ~ 85°C
• Internal Switch(s): No
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Output: -
• Current - Output / Channel: -
• Efficiency: -

OPERATION
For applications where the RUN pin is only to be used as
a logic input, the user should be aware of the 7V Absolute
Maximum Rating for this pin! The RUN pin can be con-
nected to the input voltage through an external 1M resistor,
as shown in Figure 5c, for “always on” operation.
Soft-Start Capacitor Selection
For proper soft-start operation, the LTC3783 should have
a suffi ciently large soft-start capacitor, C
the SS pin. The minimum soft-start capacitor size can be
estimated on the basis of output voltage, capacitor size
and load current. In addition, PWM operation reduces the
effective SS capacitor value by the dimming ratio.
C
SS MIN
(
)
LOGIC CONTROL
>
Figure 5b. On/Off Control Using External Logic
EXTERNAL
2
• dimmin
g ratio
RUN
SUPPLY
Figure 5a. Programming the Turn-On and Turn-Off Thresholds Using the RUN Pin
INPUT
•
50
150
6V
μ
1.248V
A C
+
–
CAPACITOR
mV
OPTIONAL
•
FILTER
OUT
• .
1 2
+
–
•
V
3483 F05b
V
COMPARATOR
OUT
SS
RUN
•
R2
R1
, attached to
R
DS
(
O O N SENSE
)/
V
RUN
GND
IN
REFERENCE
μPOWER
6V
1.248V
assuming 50% ripple current, where R
represents either the R
or R
ratio is described by 1/D
Application Circuits
A basic LTC3783 PWM-dimming LED application is shown
on the fi rst page of this data sheet.
Operating Frequency and PWM Dimming Ratio
The minimum operating frequency, f
operation of a PWM dimming application depends on the
minimum PWM frequency, f
and N, the number of f
f
OSC
+
–
SENSE
SUPPLY
INPUT
>
, whichever is used on the SENSE pin. Dimming
N f
COMPARATOR
Figure 5c. External Pull-Up Resistor on
RUN Pin for “Always On” Operation
D
+
–
•
PWM
RUN
PWM
1M
R2
OSC
BIAS AND
START-UP
CONTROL
DS(ON)
V
RUN
GND
IN
PWM
PWM
cycles per PWM cycle:
3783 F05a
as shown in Figure 6.
1.248V
6V
of the switching MOSFET
, the dimming ratio 1/D
OSC
+
–
, required for proper
LTC3783
COMPARATOR
3483 F05c
DS(ON)/SENSE
RUN
13
PWM
3783fb
,