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参数资料
| 型号： | TC3684EUART |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHED CAPACITOR CONVERTER, 170 kHz SWITCHING FREQ-MAX, PDSO8 |
| 封装： | MSOP-8 |
| 文件页数： | 3/7页 |
| 文件大小： | 960K |
| 代理商： | TC3684EUART |
3
TC3682/3/4-1 8/14/00
TC3682
TC3683
TC3684
Inverting Charge Pump Voltage
Doublers with Active Low Shutdown
2001 Microchip Technology Inc.
DS21556A
DETAILED DESCRIPTION
The TC3682, TC3683 and TC3684 charge pumps per-
form –2x multiplication of the voltage applied to the VIN pin.
Conversion is performed using two synchronous switching
matrices and three external capacitors.
When the shut-
down input is held at a logic low, both stages go into a very
low power mode of operation consuming less than 1
A of
supply current.
Figure 1 (below) is a block diagram representation of the
TC3682, TC3683 and TC3684 architecture. The first switch-
ing stage inverts the voltage present at VIN and the second
stage uses ‘–VIN’ generated from the first stage to produce
the ‘–2x’ output function from the second stage switching matrix.
Each device contains an on-board oscillator that syn-
chronously controls the operation of the charge pump switch-
ing matrices. The TC3682 synchronously switches at 12kHz,
the TC3683 synchronously switches at 35kHz, and the
TC3684 synchronously switches at 125kHz. The different
oscillator frequencies for this device family allow the user to
trade-off capacitor size versus supply current. Faster oscil-
lators can use smaller external capacitors, but will consume
more supply current (see Electrical Characteristics Table).
When the shutdown input is in a low state, the oscillator
and both switch matrices are powered off placing the TC3682,
TC3683 and TC3684 in the shutdown mode. When the VIN
supply input is powered from an external battery, the shut-
down mode minimizes power consumption, which in turn will
extend the life of the battery.
Figure 1. Functional Block Diagram
APPLICATIONS INFORMATION
Output Voltage Considerations
The TC3682, TC3683 and TC3684 perform inverting
voltage conversions but do not provide any type of regula-
tion. The output voltage will droop in a linear manner with
respect to the respective load currents. The value of the
equivalent output resistance of the ‘-VIN’ output is approxi-
mately 50
nominal at +25°C and VIN = +5V. The value of
the ‘-2VIN’ output and is approximately 140 nominal at
+25
°C and VIN = +5V. In this particular case, ‘-VIN’ is
approximately – 5V and ‘–2VIN’ is approximately –10V at
very light loads, and each stage will droop according to the
equation below:
VDROOP = IOUT x ROUT
Capacitor Selection
In order to maintain the lowest output resistance and
output ripple voltage, it is recommended that low ESR
capacitors be used. Additionally, larger values of C1 and C2
will lower the output resistance and larger values of COUT will
reduce output ripple. NOTE: For proper charge pump
operation, C1 must have a voltage rating greater than or
equal to VIN, while C2 and COUT must have a voltage
rating greater than or equal to 2VIN.
Table 1 shows various values of C1/C2 and the corre-
sponding output resistance values for VIN=5V @ +25°C.
Table 2 shows the output voltage ripple for various
values of COUT (again assuming VIN = 5V @ +25oC). The
VRIPPLE values assume a 1mA output load current and a
0.1
ESRCOUT.
—2VIN
—VIN
+
COUT1
COUT2
VIN
SWITCH MATRIX
(1st STAGE)
SWITCH MATRIX
(2nd STAGE)
OSCILLATOR
SHDN
ENABLE
C1
+
C2
+
Table 1. Output Resistance vs. C1/C2 (ESR = 0.1
).
C1,C2
TC3682
TC3683
TC3684
(
F)
ROUT (
)ROUT ()
ROUT (
)
0.33
633
184
120
1
262
120
102
3.3
120
95
84
Table 2. Output Voltage Ripple vs. COUT (ESR = 0.1) IOUT = 1mA
COUT
TC3682 VRIPPLE
TC3683 VRIPPLE
TC3684 VRIPPLE
(
F)
(mV)
0.33
192
60
27
163
21
16
3.3
17
8
7
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