参数资料
| 型号： | LTC3216EDE#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 7/12页 |
| 文件大小： | 0K |
| 描述： | IC CHARGE PUMP LED 12-DFN |
| 标准包装： | 2,500 |
| 应用： | 转换器，高电流 LED |
| 输入电压： | 2.9 V ~ 4.4 V |
| 输出数： | 1 |
| 输出电压： | 多重 |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 12-WFDFN 裸露焊盘 |
| 供应商设备封装： | 12-DFN（4x3） |
| 包装： | 带卷 (TR) |
LTC3216
OPERATION
connected between the I SET2 or I SET1 pin and GND. The
resistor values needed to attain the desired current levels
can be determined by equation 1.
Charge Pump Strength
When the LTC3216 operates in either the 1.5x mode or
2x mode, the charge pump can be modeled as a Theve-
R SET1/2 = 3965/I LED
(1)
nin-equivalent circuit to determine the amount of current
A resistor value of 2kΩ or less (i.e. a short-circuit) will
cause the LTC3216 to enter overcurrent shutdown mode.
available from the effective input voltage and effective
open-loop output resistance, R OL (Figure 1).
This mode will prevent damage to the part by shutting
down the high power sections of the chip.
R OL
+
Regulation is achieved by sensing the voltage at the CPO
pin and modulating the charge pump strength based
on the error signal. The CPO regulation voltages are set
1.5V IN
OR
2V IN
+
–
CPO
–
internally, and are dependent on the charge pump mode
as shown in Table 1.
Table 1. Charge Pump Output Regulation Voltages
Figure 1. Charge Pump Open-Loop Thevenin-Equivalent Circuit
R OL is dependent on a number of factors including the
CHARGE PUMP MODE
1.5x
2x
V CPO
4.6V
5.1V
oscillator frequency, ?ying capacitor values and switch
resistances.
From Figure 1, we can see that the output current is
In shutdown mode all circuitry is turned off and the
proportional to:
LTC3216 draws a very low current from the V IN supply.
Furthermore, CPO is weakly connected to V IN . The LTC3216
enters shutdown mode when both the EN1 and EN2 pins
(1.5V IN – CPO)/R OL or (2V IN – CPO)/R OL
in the 1.5x mode or 2x mode respectively.
(2)
are brought low. Since EN1 and EN2 are high impedance
CMOS inputs they should never be allowed to ?oat. To
ensure that their states are de?ned they must always be
driven with valid logic levels.
Thermal Protection
The LTC3216 has built-in overtemperature protection. Ther-
mal shutdown circuitry will shutdown the I LED output when
the junction temperature exceeds approximately 150°C. It
will re-enable the I LED output once the junction temperature
drops back to approximately 135°C. The LTC3216 will cycle
in and out of thermal shutdown inde?nitely without latch
up or damage until the heat source is removed.
Soft-Start
To prevent excessive inrush current during start-up and
mode switching, the LTC3216 employs built-in soft-start
circuitry. Soft-start is achieved by increasing the amount
of current available to the output charge storage capacitor
linearly over a period of approximately 250μs.
Current Levels
The LTC3216 may be programmed to have three discrete
current levels. These are the LOW, HIGH and LOW +
HIGH current levels. The LOW and HIGH currents are set
by the resistors connected between I SET1 and I SET2 pins,
respectively, to GND. The LOW + HIGH current mode
supplies a current that is equal to sum of the LOW and
HIGH currents.
Due to the low output impedance of this part, care should
be taken in selecting current levels. This part can supply up
to 500mA continuously, and up to 1A for pulsed operation
with a 10% duty cycle. Pulsed operation may be achieved
by toggling the EN1 and EN2 bits. In either continuous
or pulsed operation, proper board layout is required for
effective heat sinking.
Mode Switching
The LTC3216 will automatically switch from 1x mode to
1.5x mode, and subsequently from 1.5x mode to 2x mode
3216fc
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