参数资料
型号: MAX1853EXT-T
厂商: Maxim Integrated Products
文件页数: 6/8页
文件大小: 0K
描述: IC REG SWITCHED CAP INV SC70-6
产品培训模块: Lead (SnPb) Finish for COTS
Obsolescence Mitigation Program
标准包装: 2,500
类型: 切换式电容器(充电泵),反相
输出类型: 可调式
输出数: 1
输出电压: -2.5 V ~ -5.5 V
输入电压: 2.5 V ~ 5.5 V
频率 - 开关: 110kHz ~ 310kHz
电流 - 输出: 30mA
同步整流器:
工作温度: -40°C ~ 85°C
安装类型: 表面贴装
封装/外壳: 6-TSSOP,SC-88,SOT-363
包装: 带卷 (TR)
供应商设备封装: SC-70-6
SC70 Inverting Charge Pumps
with Shutdown
IN
S1
S2
V+
R EQUIV
V OUT
S3
C1
S4
C2
R EQUIV =
1
f OSC ? C1
C2
R L
Figure 2. Ideal Voltage Inverter
f OSC
V OUT = -(V IN )
Figure 3b. Equivalent Circuit
Paralleling Devices
Paralleling multiple MAX1852/MAX1853s reduces the
output resistance. Each device requires its own pump
capacitor (C1), but the reservoir capacitor (C2) serves
all devices (Figure 5). Increase C2 ’ s value by a factor of
V+
V OUT
n , where n is the number of parallel devices. Figure 5
shows the equation for calculating output resistance.
C1
C2
R L
Combined Doubler/Inverter
In the circuit of Figure 6, capacitors C1 and C2 form the
inverter, while C3 and C4 form the doubler. C1 and C3
are the pump capacitors; C2 and C4 are the reservoir
Figure 3a. Switched-Capacitor Model
capacitors. Because both the inverter and doubler use
part of the charge-pump circuit, loading either output
causes both outputs to decline toward GND. Make sure
V RIPPLE =
I OUT
2(f OSC )C2
+ 2 × I OUT × ESR C2
the sum of the currents drawn from the two outputs
does not exceed 30mA.
Heavy Load Connected to a
Input Bypass Capacitor (C3)
If necessary, bypass the incoming supply to reduce its
AC impedance and the impact of the MAX1852/
MAX1853s ’ switching noise. A bypass capacitor with a
value equal to that of C1 is recommended.
Voltage Inverter
The most common application for these devices is a
charge-pump voltage inverter (Figure 1). This applica-
tion requires only two external components — capacitors
C1 and C2 — plus a bypass capacitor, if necessary.
Refer to the Capacitor Selection section for suggested
capacitor types.
Cascading Devices
Two devices can be cascaded to produce an even
larger negative voltage (Figure 4). The unloaded output
voltage is normally -2 ? V IN , but this is reduced slightly
by the output resistance of the first device multiplied by
the quiescent current of the second. When cascading
more than two devices, the output resistance rises sig-
nificantly. For applications requiring larger negative
voltages, see the MAX865 and MAX868 data sheets.
Positive Supply
Under heavy loads, where a higher supply is sourcing
current into OUT, the OUT supply must not be pulled
above ground. Applications that sink heavy current into
OUT require a Schottky diode (1N5817) between GND
and OUT, with the anode connected to OUT (Figure 7).
Layout and Grounding
Good layout is important, primarily for good noise per-
formance. To ensure good layout, mount all compo-
nents as close together as possible, keep traces short
to minimize parasitic inductance and capacitance, and
use a ground plane.
6
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