LTC3217_15 Datasheet, PDF (11/12 Pages) Linear Technology – 600mA Low Noise Multi-LED Camera Light Charge Pumps

LTC3217
PACKAGE DESCRIPTION
At moderate to high output power, the quiescent current
of the LTC3217 is negligible and the expression shown in
Equation 6 is valid.
Once dropout is detected at the LED pin, the LTC3217
enables the charge pump in 1.5x mode.
In 1.5x boost mode, the efficiency is similar to that of a
linear regulator with an effective input voltage of 1.5 times
the actual input voltage. This is because the input current
for a 1.5x charge pump is approximately 1.5 times the
load current. In an ideal 1.5x charge pump, the power
efficiency would be given by:
η_IDEAL
=
P_LED
P_IN
=
(V_LED • I_LED)
(V_BAT • (1.5) • I_LED)
=
V_{LED (7)}
(1.5 • V_BAT )
Similarly, in 2x boost mode, the efficiency is similar to
that of a linear regulator with an effective input voltage
of 2 times the actual input voltage. In an ideal 2x charge
pump, the power efficiency would be given by:
η_IDEAL
= ^PLED
P_IN
= ^{(VLED • ILED)} = ^VLED
(V_BAT • (2) • I_LED) (2 • V_BAT )
(8)
Thermal Management
For higher input voltages and maximum output current,
there can be substantial power dissipation in the LTC3217.
If the junction temperature increases above approximately
150°C the thermal shutdown circuitry will automatically
deactivate the output current sources and charge pump.
To reduce maximum junction temperature, a good thermal
connection to the PC board is recommended. Connecting
the Exposed Pad to a ground plane and maintaining a solid
ground plane under the device will reduce the thermal
resistance of the package and PC board considerably.
PACKAGE DESCRIPTION
3.50 ± 0.05
1.45 ± 0.05
2.10 ± 0.05 ^{(4 SIDES)}
UD Package
16-Lead Plastic QFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1691)
0.70 ±0.05
3.00 ± 0.10
(4 SIDES)
PIN 1
TOP MARK
(NOTE 6)
0.75 ± 0.05
BOTTOM VIEW—EXPOSED PAD
R = 0.115
TYP
15 16
PIN 1 NOTCH R = 0.20 TYP
OR 0.25 × 45° CHAMFER
0.40 ± 0.10
1
1.45 ± 0.10
2
(4-SIDES)
PACKAGE
OUTLINE
0.25 ±0.05
0.50 BSC
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
NOTE:
1. DRAWING CONFORMS TO JEDEC PACKAGE OUTLINE MO-220 VARIATION (WEED-2)
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
0.200 REF
0.00 – 0.05
(UD16) QFN 0904
0.25 ± 0.05
0.50 BSC
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION
ON THE TOP AND BOTTOM OF PACKAGE
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
3217fa
11