参数资料
| 型号： | LTC660CS8#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 6/12页 |
| 文件大小： | 0K |
| 描述： | IC REG DBL INV ADJ 0.1A 8SOIC |
| 标准包装： | 2,500 |
| 类型： | 倍增器，反相 |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | -1.5 V ~ -5.5 V，5 V ~ 11 V |
| 输入电压： | 1.5 V ~ 5.5 V，2.5 V ~ 5.5 V |
| 频率 - 开关： | 10kHz，80kHz |
| 电流 - 输出： | 100mA |
| 同步整流器： | 无 |
| 工作温度： | 0°C ~ 70°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 8-SOIC（0.154"，3.90mm 宽） |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 8-SOIC |
LTC660
APPLICATIO N S I N FOR M ATIO N
Theory of Operation
V +
To understand the theory of operation for the LTC660, a
review of a basic switched-capacitor building block is
helpful. In Figure 2, when the switch is in the left position,
capacitor C1 will charge to voltage V1. The total charge on
BOOST
4.5 ×
(1)
OSC
(8)
+2
φ
SW1
CAP +
(2)
+
C1
SW2
C1 will be q1 = C1V1. The switch then moves to the right,
discharging C1 to voltage V2. After this discharging time,
OSC
(7)
φ
CAP –
(4)
V OUT
(5)
the charge on C1 is q2 = C1V2. Note that charge has been
transferred from the source V1 to the output V2. The
C2
amount of charge transferred is:
? q = q1 – q2 = C1 (V1 – V2)
LV
(6)
CLOSED WHEN
V + > 3.0V
GND
(3)
LTC660 ? F04
If the switch is cycled “f” times per second, the charge
transfer per unit time (i.e., current) is:
I = f ? ? q = f ? C1 (V1 – V2)
Rewriting in terms of voltage and impedance equivalence,
Figure 4. LTC660 Switched-Capacitor Voltage Converter
Block Diagram
This simplified circuit does not include finite on-resistance
of the switches and output voltage ripple, however, it does
give an intuitive feel for how the device works. For ex-
I =
V1 ? V 2
1 / fC 1
=
V1 ? V 2
R EQUIV
ample, if you examine power conversion efficiency as a
function of frequency this simple theory will explain how
the LTC660 behaves. The loss and hence the efficiency is
A new variable R EQUIV has been defined such that
R EQUIV = 1/fC1. Thus, the equivalent circuit for the switched-
capacitor network is as shown in Figure 3.
Figure 4 shows that the LTC660 has the same switching
action as the basic switched-capacitor building block.
set by the output impedance. As frequency is decreased,
the output impedance will eventually be dominated by the
1/fC1 term and voltage losses will rise decreasing the
efficiency. As the frequency increases the quiescent cur-
rent increases. At high frequency this current loss be-
comes significant and the power efficiency starts to de-
crease.
V1
C1
C2
R L
V2
The LTC660 oscillator frequency is designed to run where
the voltage loss is a minimum. With the external 150 μ F
capacitors the effective output impedance is determined
660 F02
Figure 2. Switched-Capacitor Building Block
by the internal switch resistances and the capacitor ESRs.
LV (Pin 6)
V1
R EQUIV
C2
R L
V2
The internal logic of the LTC660 runs between V + and LV
(Pin 6). For V + ≥ 3V, an internal switch shorts LV to ground
(Pin 3). For V + < 3V, the LV pin should be tied to ground.
For V + ≥ 3V, the LV pin can be tied to ground or left floating.
OSC (Pin 7) and BOOST (Pin 1)
R EQUIV =
1
fC1
660 F03
The switching frequency can be raised, lowered or driven
6
Figure 3. Switched-Capacitor Equivalent Circuit
from an external source. Figure 5 shows a functional
diagram of the oscillator circuit.
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