参数资料
型号: MAX1697TEUT+T
厂商: Maxim Integrated Products
文件页数: 8/13页
文件大小: 0K
描述: IC REG SWITCHED CAP INV SOT23-6
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: -1.5 V ~ -5.5 V
输入电压: 1.6 V ~ 5.5 V
频率 - 开关: 60kHz ~ 200kHz
电流 - 输出: 60mA
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: SOT-23-6
包装: 带卷 (TR)
供应商设备封装: SOT-6
60mA, SOT23 Inverting Charge Pump
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
Thermal Shutdown
The MAX1697 has a thermal shutdown mode for addi-
tional protection against fault conditions. When the tem-
perature of the die exceeds +150°C, the internal clock
stops, suspending the device ’s operation. The
V+
V OUT
MAX1697 resumes operation when the die temperature
falls 15°C. This prevents the device from rapidly oscil-
lating around the temperature trip point.
C1
C2
R L
Applications Information
Capacitor Selection
R OUT ?
+ 2R SW C1 C2
+ 4ESR
+ ESR
( )
Figure 3a. Switched-Capacitor Model
where the output impedance is roughly approximated
by:
1
f OSC x C1
The first term is the effective resistance of an ideal
switched-capacitor circuit (Figures 3a and 3b), and
R SW is the sum of the charge pump’s internal switch
resistances (typically 4 Ω to 5 Ω at V IN = +5V). The typi-
cal output impedance is more accurately determined
from the Typical Operating Characteristics .
Current Limit
The MAX1697 limits its input current upon start-up to
170mA (typ). This prevents low-current or higher output
impedance input supplies (such as alkaline cells) from
being overloaded when power is applied or when the
The charge-pump output resistance is a function of the
ESR of C1 and C2. To maintain the lowest output resis-
tance, use capacitors with low ESR. (See Table 1 for a
list of recommended manufacturers.) Tables 2 and 3
suggest capacitor values for minimizing output resis-
tance or capacitor size.
Flying Capacitor (C1)
Increasing the flying capacitor’s value reduces the out-
put resistance. Above a certain point, increasing C1’s
capacitance has negligible effect because the output
resistance is then dominated by internal switch resis-
tance and capacitor ESR.
Output Capacitor (C2)
Increasing the output capacitor’s value reduces the
output ripple voltage. Decreasing its ESR reduces both
output resistance and ripple. Lower capacitance values
can be used with light loads if higher output ripple can
be tolerated. Use the following equation to calculate the
peak-to-peak ripple:
device awakes from shutdown.
Shutdown
The MAX1697 has a logic-controlled shutdown input.
V RIPPLE =
I OUT
2(f OSC )C2
+ 2 × I OUT × ESR C2
Driving SHDN low places the device in a low-power
shutdown mode. The charge-pump switching halts,
supply current is reduced to 2nA, and OUT is actively
pulled to ground through a 3 Ω resistance.
Driving SHDN high will restart the charge pump. The
switching frequency and capacitor values determine
how soon the device will reach 90% of the input voltage.
Input Bypass Capacitor (C3)
If necessary, bypass the incoming supply to reduce its
AC impedance and the impact of the MAX1697’s switch-
ing noise. A bypass capacitor with a value equal to that
of C1 is recommended.
8
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