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PDF MAX667ESA Data sheet ( Hoja de datos )
| Número de pieza | MAX667ESA | |
| Descripción | +5V/Programmable Low-Dropout Voltage Regulator | |
| Fabricantes | Maxim Integrated | |
| Logotipo |  |
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19-3894; Rev 3; 10/94
+5V/Programmable Low-Dropout
Voltage Regulator
_______________General Description
The MAX667 low-dropout, positive, linear voltage regu-
lator supplies up to 250mA of output current. With no
load, it has a typical quiescent current of 20µA. At
200mA of output current, the input/output voltage differ-
ential is typically 150mV. Other features include a low-
voltage detector to indicate power failure, as well as
early-warning and low-dropout detectors to indicate an
imminent loss of output voltage regulation. A shutdown
control disables the output and puts the circuit into a
low quiescent-current mode.
The MAX667 employs Dual Mode™ operation. One
mode uses internally trimmed feedback resistors to pro-
duce +5V. In the other mode, the output may be varied
from +1.3V to +16V by connecting two external resistors.
The MAX667 is a pin-compatible upgrade to the
MAX666 in most applications where the input voltages
are above +3.5V. Choose the MAX667 when high out-
put currents and/or low dropout voltages are desired,
as well as for improved performance at higher
temperatures.
________________________Applications
Battery-Powered Devices
Pagers and Radio Control Receivers
Portable Instruments
Solar-Powered Instruments
____________________________Features
o 350mV Max Dropout at 200mA
o 250mA Output Current
o Normal Mode: 20µA Typ Quiescent Current
Shutdown Mode: 0.2µA Typ Quiescent Current
o Low-Battery Detector
o Fixed +5V (Min Component Count) or
Adjustable Output
o +3.5V to +16.5V Input
o Dropout Detector Output
o 10µF Output Capacitor
______________Ordering Information
PART
MAX667CPA
MAX667CSA
MAX667C/D
MAX667EPA
MAX667ESA
MAX667MJA
TEMP. RANGE
0°C to +70°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
-55°C to +125°C
* Contact factory for dice specifications.
PIN-PACKAGE
8 Plastic DIP
8 SO
Dice*
8 Plastic DIP
8 SO
8 CERDIP
__________Typical Operating Circuit
+6.3V
BATTERY
IN OUT
MAX667
+5V OUT
C1
10µF
SET GND SHDN
__________________Pin Configuration
TOP VIEW
DD 1
OUT 2
LBI 3
GND 4
MAX667
DIP/SO
8 IN
7 LBO
6 SET
5 SHDN
TM Dual Mode is a trademark of Maxim Integrated Products.
________________________________________________________________ Maxim Integrated Products 1
Call toll free 1-800-998-8800 for free samples or literature.
1 page  
+5V/Programmable Low-Dropout
Voltage Regulator
Output-Voltage Selection
If SET is connected to a resistive voltage divider (Figure
3), the output voltage is set by the equation:
VOUT = VSET x (R1 + R2) / R1,
where VSET = 1.22V
To simplify resistor selection:
R2 = R1 x (VOUT / VSET - 1)
Since the input bias current at SET has a maximum
value of 10nA, relatively large values can be used for
R1 and R2 with no loss of accuracy. 1MΩ is a typical
value for R1. The VSET tolerance is less than ±25mV.
This allows the output to be preset without trim pots,
using only fixed resistors in most cases. However,
when resistor values greater than 1MΩ are used, pay
special attention to printed circuit board leakage that
can introduce error at the SET input.
Shutdown (Standby) Mode
SHDN puts the device into standby mode to conserve
power. When this pin is held low, the IC operates nor-
mally. If it is driven above 1.5V, the chip shuts down.
Quiescent current of the MAX667 is then reduced to
less than 1µA, and OUT turns off.
Note that the voltage for SHDN must never be more
than 0.3V higher than VIN.
Low-Battery Function
The MAX667 contains circuitry for low-battery detec-
tion. If the voltage at LBI falls below the regulator’s
internal reference (1.22V), LBO, an open-drain output,
sinks current to GND. The threshold can be set to any
level above the reference voltage by connecting a
resistive divider to LBI based on the equation:
R3 = R4 x (VBATT / VLBI - 1)
where VBATT is the desired threshold of the low-battery
detector, and R3 and R4 are the LBI input divider
resistors.
Since LBI input current is no more than 10nA, high val-
ues for R3 and R4 minimize loading. If VOUT is 5V, a
5.5V low-battery threshold can be set using 8.2MΩ for
R3 and 2.4MΩ for R4. When resistor values greater
than 1MΩ are used, pay special attention to PC board
leakage that can introduce error at the LBI input.
When the voltage at LBI is below the internal threshold,
LBO sinks current to GND. A pull-up resistor of 10kΩ or
more connected to OUT can be used with this pin when
driving CMOS circuits. Any pull-up resistor connected
to LBO should not be returned to a voltage source
greater than VOUT. When LBI is above the threshold or
the MAX667 is in SHDN mode, the LBO output is off.
Dropout Detector
The minimum input-output differential, or dropout volt-
age, determines the regulator’s lowest usable input
voltage. In battery-operated systems, this determines
the useful end-of-life battery voltage. The MAX667 fea-
tures very low dropout voltage (see Electrical
Characteristics). In addition, the MAX667 has a dropout
detector output, DD, that changes as the dropout volt-
age approaches its limit. DD is an open collector of a
PNP transistor. The dropout voltage and the dropout
detector both depend on the output current and tem-
perature. When the input voltage is more than 300mV
above the output voltage, the dropout detector will not
conduct. As the differential decreases below 300mV,
the DD source current increases abruptly. This current
signals a warning that regulation is about to be lost.
Connecting a resistor (typically 100kΩ) from DD to
ground develops a voltage that can be monitored by
analog circuits or changed to digital levels by a com-
parator. LBI may be used for this purpose.
__________Applications Information
Output Capacitor
As with all PNP output regulators, an output capacitor
(C1, Figure 2) is required to maintain stability. 10µF is
recommended. To ensure stability, the output-capacitor
ESR must be sufficiently high. Figure 4 shows the mini-
mum required output-capacitor ESR for a given temper-
ature. Alternatively, a resistor may be added in series
with the output capacitor (Figure 5); the sum of the out-
5
4
3
2
1
0
-60 -40 -20 0 20 40 60 80 100 120
TEMPERATURE (˚C)
Figure 4. Minimum Required Output-Capacitor ESR vs.
Temperature
_______________________________________________________________________________________ 5
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