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PDF MAX1720 Data sheet ( Hoja de datos )
| Número de pieza | MAX1720 | |
| Descripción | Switched-Capacitor Voltage Inverters | |
| Fabricantes | Maxim Integrated | |
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Hay una vista previa y un enlace de descarga de MAX1720 (archivo pdf) en la parte inferior de esta página. Total 8 Páginas | ||
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19-1439; Rev 2; 4/04
SOT23, Switched-Capacitor
Voltage Inverters with Shutdown
General Description
The ultra-small MAX1719/MAX1720/MAX1721 monolithic,
CMOS charge-pump inverters accept input voltages
ranging from +1.5V to +5.5V. The MAX1720 operates at
12kHz, and the MAX1719/MAX1721 operate at 125kHz.
High efficiency, small external components, and logic-
controlled shutdown make these devices ideal for both
battery-powered and board-level voltage conversion
applications.
Oscillator control circuitry and four power MOSFET
switches are included on-chip. A typical MAX1719/
MAX1720/MAX1721 application is generating a -5V
supply from a +5V logic supply to power analog circuitry.
All three parts come in a 6-pin SOT23 package and can
deliver a continuous 25mA output current.
For pin-compatible SOT23 switched-capacitor voltage
inverters without shutdown (5-pin SOT23), see the
MAX828/MAX829 and MAX870/MAX871 data sheets. For
applications requiring more power, the MAX860/MAX861
deliver up to 50mA. For regulated outputs (up to -2 x VIN),
refer to the MAX868. The MAX860/MAX861 and MAX868
are available in space-saving µMAX packages.
Applications
Local Negative Supply from a Positive Supply
Small LCD Panels
GaAs PA Bias Supply
Handy-Terminals, PDAs
Battery-Operated Equipment
Typical Operating Circuit
Features
♦ 1nA Logic-Controlled Shutdown
♦ 6-Pin SOT23 Package
♦ 99.9% Voltage Conversion Efficiency
♦ 50µA Quiescent Current (MAX1720)
♦ +1.5V to +5.5V Input Voltage Range
♦ 25mA Output Current
♦ Requires Only Two 1µF Capacitors
(MAX1719/MAX1721)
Ordering Information
PART
MAX1719EUT
MAX1720EUT
MAX1721EUT
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-
PACKAGE
6 SOT23-6
6 SOT23-6
6 SOT23-6
SOT
TOP MARK
AACA
AABS
AABT
Pin Configuration
1µF
INPUT
1.5V to 5.5V
C1+
IN
C1-
OUT
MAX1721
ON SHDN
OFF
GND
NEGATIVE
OUTPUT
-1 · VIN
25mA
1µF
TOP VIEW
OUT 1
6 C1+
IN 2
C1- 3
MAX1719
MAX1720
MAX1721
5 SHDN (SHDN)
4 GND
( ) ARE FOR MAX1719
SOT23-6
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1 page  
SOT23, Switched-Capacitor
Voltage Inverters with Shutdown
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VIN = +5V, SHDN = GND (MAX1719), SHDN = IN (MAX1720/MAX1721), C1 = C2 = C3, TA = +25°C, unless
otherwise noted.)
MAX1721
START-UP FROM SHUTDOWN
MAX1720/21toc13
VOUT
2V/div
RL = 1kΩ
50µs/div
VSHDN
5V/div
MAX1719/MAX1721
OUTPUT CURRENT vs. CAPACITANCE
35
30 VIN = +4.75V, VOUT = -4.0V
25
20 VIN = +3.15V, VOUT = -2.5V
15
10
VIN = +1.9V, VOUT = -1.5V
5
0
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
CAPACITANCE (µF)
MAX1719/MAX1721
OUTPUT VOLTAGE RIPPLE vs. CAPACITANCE
400
350
300
VIN = +4.75V, VOUT = -4.0V
250
200 VIN = +3.15V, VOUT = -2.5V
150 VIN = +1.9V, VOUT = -1.5V
100
50
0
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
CAPACITANCE (µF)
PIN
MAX1719
MAX1720
MAX1721
11
22
33
44
5–
–5
66
NAME
OUT
IN
C1-
GND
SHDN
SHDN
C1+
Pin Description
FUNCTION
Inverting Charge-Pump Output
Power-Supply Positive Voltage Input
Negative Terminal of Flying Capacitor
Ground
Noninverting Shutdown Input. Drive this pin low for normal operation; drive it high for
shutdown mode. OUT is actively pulled to ground during shutdown.
Inverting Shutdown Input. Drive this pin high for normal operation; drive it low for
shutdown mode. OUT is actively pulled to ground during shutdown.
Positive Terminal of Flying Capacitor
Detailed Description
The MAX1719/MAX1720/MAX1721 capacitive charge
pumps invert the voltage applied to their input. For high-
est performance, use low equivalent series resistance
(ESR) capacitors (e.g., ceramic).
During the first half-cycle, switches S2 and S4 open,
switches S1 and S3 close, and capacitor C1 charges to
the voltage at IN (Figure 2). During the second half-
cycle, S1 and S3 open, S2 and S4 close, and C1 is level
shifted downward by VIN volts. This connects C1 in par-
allel with the reservoir capacitor C2. If the voltage across
C2 is smaller than the voltage across C1, charge flows
from C1 to C2 until the voltage across C2 reaches
-VIN. The actual voltage at the output is more positive
than -VIN, since switches S1–S4 have resistance and the
load drains charge from C2.
_______________________________________________________________________________________ 5
5 Page | ||
| Páginas | Total 8 Páginas | |
| PDF Descargar | [ Datasheet MAX1720.PDF ] | |
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