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参数资料
| 型号： | LTC3204BEDC-5#TR |
| 厂商： | Linear Technology |
| 文件页数： | 8/12页 |
| 文件大小： | 0K |
| 描述： | IC REG SWITCHED CAP DBL 5V 6DFN |
| 标准包装： | 2,500 |
| 类型： | 切换式电容器（充电泵），倍增器 |
| 输出类型： | 固定 |
| 输出数： | 1 |
| 输出电压： | 5V |
| 输入电压： | 2.7 V ~ 5.5 V |
| PWM 型： | Burst Mode? |
| 频率 - 开关： | 1.2MHz |
| 电流 - 输出： | 150mA |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 6-WFDFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 6-DFN-EP（2x2） |
LTC3204-3.3/LTC3204-5/
LTC3204B-3.3/LTC3204B-5
APPLICATIO S I FOR ATIO
= = OUT
P OUT V OUT ? I OUT V
R OL ? 2 ∑ R S +
POWER EF?CIENCY
THE POWER EF?CIENCY ( η ) OF THE LTC3204-3.3/LTC3204-5/
LTC3204B-3.3/LTC3204B-5 IS SIMILAR TO THAT OF A LINEAR
REGULATOR WITH AN EFFECTIVE INPUT VOLTAGE OF TWICE THE ACTUAL
INPUT VOLTAGE. THIS OCCURS BECAUSE THE INPUT CURRENT FOR A
VOLTAGE DOUBLING CHARGE PUMP IS APPROXIMATELY TWICE THE
OUTPUT CURRENT. IN AN IDEAL REGULATING VOLTAGE DOUBLER THE
POWER EF?CIENCY WOULD BE GIVEN BY:
η=
P IN V IN ? 2 I OUT 2 V IN
AT MODERATE TO HIGH OUTPUT POWER, THE SWITCHING LOSSES
AND THE QUIESCENT CURRENT OF THE LTC3204-3.3/LTC3204-5/
LTC3204B-3.3/LTC3204B-5 ARE NEGLIGIBLE AND THE EXPRES-
SION ABOVE IS VALID. FOR EXAMPLE, WITH V IN = 3V, I OUT =
100MA AND V OUT REGULATING TO 5V, THE MEASURED EF?CIENCY
IS 81.8% WHICH IS IN CLOSE AGREEMENT WITH THE THEORETICAL
83.3% CALCULATION.
(F OSC ), VALUE OF THE ?YING CAPACITOR (C FLY ), THE NONOVERLAP
TIME, THE INTERNAL SWITCH RESISTANCES (R S ), AND THE ESR OF
THE EXTERNAL CAPACITORS. A ?RST ORDER APPROXIMATION FOR
R OL IS GIVEN BELOW:
1
S=1 TO 4 F OSC ? C FLY
TYPICAL R OL VALUES AS A FUNCTION OF TEMPERATURE ARE SHOWN
IN FIGURE 2.
8
V IN = 2.7V
V OUT = 4.5V
7
6
5
MAXIMUM AVAILABLE OUTPUT CURRENT
4
–50
0
50
100
–
I OUT =
V RIPPLE ( P ? P ) ?
FOR THE LTC3204-3.3/LTC3204-5/LTC3204B-3.3/
LTC3204B-5,THE MAXIMUM AVAILABLE OUTPUT CURRENT AND
VOLTAGE CAN BE CALCULATED FROM THE EFFECTIVE OPEN-LOOP
OUTPUT RESISTANCE, R OL , AND THE EFFECTIVE INPUT VOLTAGE,
2V IN(MIN) .
R OL
+
+ 2V IN I OUT V OUT
–
3204 F01
FIGURE 1. EQUIVALENT OPEN-LOOP CIRCUIT
FROM FIG. 1, THE AVAILABLE CURRENT IS GIVEN BY:
2V IN – V OUT
R OL
EFFECTIVE OPEN LOOP OUTPUT RESISTANCE (R OL )
THE EFFECTIVE OPEN LOOP OUTPUT RESISTANCE (R OL ) OF A CHARGE
PUMP IS A VERY IMPORTANT PARAMETER WHICH DETERMINES THE
STRENGTH OF THE CHARGE PUMP. THE VALUE OF THIS PARAMETER
DEPENDS ON MANY FACTORS SUCH AS THE OSCILLATOR FREQUENCY
8
TEMPERATURE ( ° C)
3204 F02
FIGURE 2. TYPICAL R OL VS TEMPERATURE
V IN , V OUT CAPACITOR SELECTION
THE STYLE AND VALUE OF CAPACITORS USED WITH THE LTC3204-3.3/
LTC3204-5/LTC3204B-3.3/LTC3204B-5 DETERMINE SEVERAL
IMPORTANT PARAMETERS SUCH AS REGULATOR CONTROL LOOP STA-
BILITY, OUTPUT RIPPLE, CHARGE PUMP STRENGTH AND MINIMUM
START-UP TIME.
TO REDUCE NOISE AND RIPPLE, IT IS RECOMMENDED THAT LOW
ESR (<0.1 Ω ) CERAMIC CAPACITORS BE USED FOR BOTH C IN AND
C OUT . THESE CAPACITORS SHOULD BE 1μF OR GREATER. TANTALUM
AND ALUMINUM CAPACITORS ARE NOT RECOMMENDED BECAUSE
OF THEIR HIGH ESR.
THE VALUE OF C OUT DIRECTLY CONTROLS THE AMOUNT OF OUTPUT
RIPPLE FOR A GIVEN LOAD CURRENT. INCREASING THE SIZE OF C OUT
WILL REDUCE THE OUTPUT RIPPLE AT THE EXPENSE OF HIGHER
MINIMUM TURN-ON TIME. THE PEAK-TO-PEAK OUTPUT RIPPLE
IS APPROXIMATELY GIVEN BY THE EXPRESSION:
I OUT
2 F OSC ? C OUT
3204fa
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