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PDF MAX1822 Data sheet ( Hoja de datos )
| Número de pieza | MAX1822 | |
| Descripción | High-Side Power Supply | |
| Fabricantes | Maxim Integrated | |
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19-1892; Rev 0; 1/01
High-Side Power Supply
_______________General Description
The MAX1822 high-side supply, using a regulated
charge pump, generates a regulated output voltage
11V greater than the input supply voltage to power
high-side switching and control circuits. The MAX1822
allows low-resistance N-channel MOSFETs (FETs) to be
used in circuits that normally require costly, less effi-
cient P-channel FETs and PNP transistors. The high-
side output also eliminates the need for logic FETs in
+5V and other low-voltage switching circuits.
A +3.5V to +16.5V input supply range and a typical qui-
escent current of only 150µA make the MAX1822 ideal
for a wide range of line- and battery-powered switching
and control applications where efficiency is crucial.
Also provided is a logic-level power-ready output (PR)
to indicate when the high-side voltage reaches the
proper level.
The MAX1822 comes in an 8-pin SO package and
requires three inexpensive external capacitors. The
MAX1822 is a pin-for-pin replacement to the MAX622.
____________________________Features
o +3.5V to +16.5V Operating Supply Voltage Range
o Output Voltage Regulated to VCC + 11V (typ)
o 150µA (typ) Quiescent Current
o Power-Ready Output
PART
MAX1822ESA
Ordering Information
TEMP. RANGE
-40°C to +85°C
PIN-PACKAGE
8 SO
________________________Applications
High-Side Power Control with N-Channel FETs
Low-Dropout Voltage Regulators
Power Switching from Low Supply Voltages
H-Switches
Stepper Motor Drivers
Battery-Load Management
Portable Computers
Typical Operating Circuit
+3.5V TO +16.5V
0.1µF
CERAMIC
C1
C2
1
C1+
8
VCC
C3
7 C1-
VOUT 5 +12.5V TO +27.5V
6
C2+
MAX1822
2 C2-
GND
4
3
PR
Pin Configuration
TOP VIEW
C1+ 1
C2- 2
PR 3
GND 4
MAX1822
8 VCC
7 C1-
6 C2+
5 VOUT
SO
________________________________________________________________ Maxim Integrated Products 1
For price, delivery, and to place orders, please contact Maxim Distribution at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
1 page  
High-Side Power Supply
S8
C3
VINT
S7
S6
S4
C2
11V
RC OSCILLATOR
+
CONTROL LOGIC
OVERVOLTAGE
COMPARATOR
8.5V
POWER-READY
COMPARATOR
VOUT
S3
C1 S2
S1 S5
VCC
PR DRIVER
PR
TWO-STAGE CHARGE PUMP
(SWITCHES SHOWN IN REFRESH MODE)
Figure 1. MAX1822 Block Diagram
Detailed Description
Charge-Pump Operation
The MAX1822 is a multistage charge-pump power sup-
ply. Although the charge pump is capable of multiply-
ing VCC up to four times, the output is regulated to VCC
+ 11V by an internal feedback circuit for inputs above
4V. The charge pump typically operates at 90kHz, but
regulates by pulse skipping. When VOUT exceeds VCC
+ 11V, the oscillator shuts off. As VOUT dips below VCC
+ 11V, the oscillator turns on.
Power-Ready Output
The Power-Ready Output (PR) signals control circuitry
when the high-side voltage reaches a preset level. This
feature can be used to protect external FET switches
from excess dissipation and damage by preventing them
from turning on, except when adequate gate drive levels
are present. When power is applied, PR remains low until
GND
VOUT reaches approximately VCC + 8.5V. PR also goes
low if VOUT falls below this level during operation, i.e., if
the output is overloaded. The PR high level is VCC.
Applications Information
Quiescent Supply Current
MAX1822 quiescent supply current varies with VCC and
with the values of C1, C2, and C3 (Typical Operating
Characteristics). Even with no external load, the device
must still pump to overcome internal losses. Large ratios
between C3 and C1 or C2 require more charge-pump
cycles to restore VOUT. As VCC falls below 5V, quiescent
current rises fairly rapidly to about 1mA at 4V (Typical
Operating Characteristics). This rise occurs because
VOUT no longer pulse skips to regulate at low input volt-
ages; the oscillator runs continuously, so supply current
is higher. Figure 2 shows the test circuit for the
MAX1822 quiescent supply current.
_______________________________________________________________________________________ 5
5 Page | ||
| Páginas | Total 10 Páginas | |
| PDF Descargar | [ Datasheet MAX1822.PDF ] | |
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