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 V
CC
+ 11V (typ)
o
150µA (typ) Quiescent Current
o
Power-Ready Output
MAX1822
Ordering Information
PART
MAX1822ESA
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
Pin Configuration
TOP VIEW
0.1µF
CERAMIC
C1
1
7
6
C2
2
C1+
C1-
C2+
C2-
8
V
CC
V
OUT
MAX1822
PR
GND
4
3
5
C3
C1+
+12.5V TO +27.5V
C2-
PR
1
2
8
7
V
CC
C1-
C2+
V
OUT
MAX1822
3
6
5
GND
4
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.
High-Side Power Supply
MAX1822
ABSOLUTE MAXIMUM RATINGS
V
CC
......................................................................................+17V
V
OUT
....................................................................................+30V
I
OUT
...................……………………………………………….25mA
Continuous Total Power Dissipation (T
A
= +70°C)
8-pin SO (derate 5.88mW/°C above +70°C)...............471mW
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range .............................-65°C to +160°C
Lead Temperature (soldering, 10s) .................................+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V
CC
= +5V, T
A
= T
MIN
to T
MAX
, unless otherwise noted.)
PARAMETER
Supply Voltage
SYMBOL
V
CC
I
OUT
= 0, V
CC
= 3.5V,
C1 = C2 = 0.047µF, C3 = 1µF
I
OUT
= 0, V
CC
= 4.5V, C1 = C2 = 0.047µF,
C3 = 1µF
I
OUT
= 0, V
CC
= 16.5V, C1 = C2 = 0.01µF,
C3 = 1µF (Note 2)
High-Side Voltage (Note 1)
V
OUT
I
OUT
= 50µA, V
CC
= 3.5V,
C1 = C2 = 0.047µF, C3 = 1µF
I
OUT
= 250µA, V
CC
= 5V,
C1 = C2 = 0.047µF, C3 = 1µF
I
OUT
= 500µA, V
CC
= 16.5V,
C1 = C2 = 0.01µF, C3 = 1µF (Note 2)
Power-Ready Threshold
Power-Ready Output High
Power-Ready Output Low
Output Voltage Ripple
Switching Frequency
PRT
PR
OH
PR
OL
VR
F
O
I
OUT
= 0, V
CC
= 5V, C1 = C2 = 0.047µF,
C3 = 1µF, T
A
= +25°C
I
OUT
= 0, V
CC
= 16.5V, C1 = C2 = 0.047µF,
C3 = 1µF, T
A
= +25°C
I
OUT
= 0 (Note 3)
I
SOURCE
= 100µA
I
SINK
= 1mA
C1 = C2 = 0.01µF, C3 = 10µF,
I
OUT
= 1mA, V
CC
= 16.5V
50
90
150
150
500
µA
350
CONDITIONS
MIN
3.5
11.5
14.5
26.5
8.5
15
26.5
12
3.8
13.5
4.3
12.5
15.5
27.5
10.5
TYP
MAX
16.5
16.5
17.5
29.5
V
16.5
18
29.5
14.5
5
0.4
V
V
V
mV
kHz
UNITS
V
Quiescent Supply Current
IQ
Note 1:
High-side voltage measured with respect to ground.
Note 2:
For V
CC
> +13V on the MAX1822, use C1 = C2 = 0.01µF.
Note 3:
Power-Ready Threshold is the voltage with respect to ground at V
OUT
when PR switches high (PR = V
CC
).
2
_______________________________________________________________________________________
High-Side Power Supply
__________________________________________Typical Operating Characteristics
MAX1822
SUPPLY CURRENT
vs. C3 CAPACITOR VALUE
MAX1822 toc01
MAX1822
MAX1822
SUPPLY CURRENT
vs. C3 CAPACITOR VALUE
V
CC
= +16.5V
I
OUT
= 0
T
A
= +25°C
C1 = C2 = 0.01µF
MAX1822 toc02
400
C* = 0.01µF
350
SUPPLY CURRENT (µA)
300
250
200
150
100
C* = 0.1µF
50
1
2
3
4
5
6
V
CC
= +5V, I
OUT
= 0
T
A
= +25°C
C1 = C2 = C*
7
8
9
C* =
0.022µF
C* = 0.047µF
C* = 0.033µF
400
350
SUPPLY CURRENT (µA)
300
250
200
150
100
50
10
1
2
3
4
5
6
7
8
9
10
C3 CAPACITOR VALUE (µF)
C3 CAPACITOR VALUE (µF)
MAX1822
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX1822 toc03
MAX1822
MAXIMUM OUTPUT CURRENT
vs. C1 = C2 CAPACITOR VALUE
900
800
MAXIMUM I
OUT
(µA)
700
600
500
400
300
200
100
0
NOTE: MAXIMUM I
OUT
IS THE LOAD
CURRENT AT THE POINT
WHERE V
OUT
BEGINS TO
LOSE REGULATION.
0.01
C1 = C2 CAPACITANCE VALUE (µF)
0.1
V
CC
= +5V
C3 = 10µF
T
A
= +25°C
MAX1822 toc04
1.4
1.2
SUPPLY CURRENT (mA)
1.0
0.8
0.6
C1 = C2 = 0.01µF
0.4
0.2
0
2
4
6
8
10
V
CC
(V)
12
I
OUT
= 0
C3 = 1µF
T
A
= +25°C
1000
C1 = C2 = 0.47µF
14
16
18
MAX1822
OUTPUT VOLTAGE
vs. OUTPUT CURRENT
V
CC
= +5V
C3 = 10µF
T
A
= +25°C
C1 = C2 = 0.47µF
V
OUT
(V)
V
OUT
(V)
15
MAX1822 toc05
MAX1822
OUTPUT VOLTAGE
vs. OUTPUT CURRENT
V
CC
= +12V
C3 = 10µF
T
A
= +25°C
C1 = C2
0.047µF
C1 = C2
0.01µF
C1 = C2
0.022µF
MAX1822 toc05
17
24
23
22
21
20
16
14
C1 = C2 = 0.22µF
C1 = C2 = 0.01µF
12
0
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
I
OUT
(mA)
18
0
13
19
1
2
3
4
5
6
7
8
9
10
I
OUT
(mA)
_______________________________________________________________________________________
3
High-Side Power Supply
MAX1822
Typical Operating Characteristics (continued)
MAX1822
OUTPUT VOLTAGE RIPPLE
vs. RESERVOIR CAPACITOR C3
MAX1822 toc07
MAX1822
TURN-ON TIME
vs. SUPPLY VOLTAGE
I
OUT
= 0
T
A
= +25°C
MAX1822 toc08
200
180
160
V
OUT
RIPPLE (mV)
140
120
100
80
60
40
20
0
1
T
A
= +25°C
10
TURN-ON TIME (ms)
9
10
V
CC
= +16.5V
I
OUT
= 1mA
C1 = C2 = 0.01µF
V
CC
= +5V
I
OUT
= 500µA
C1 = C2 = 0.047µF
1
0.1
2
3
4
5
6
7
8
0
5
10
V
CC
(V)
15
20
RESERVOIR CAPACITOR (µF)
Pin Description
PIN
1
2
3
4
5
6
7
8
NAME
C1+
C2-
PR
GND
V
OUT
C2+
C1-
V
CC
FUNCTION
Positive terminal to primary charge-pump capacitor
Negative terminal to secondary charge-pump capacitor
Power-Ready Output. High when V
OUT
is
≥
V
CC
+ 8.5V with respect to GND.
Ground
High-Side Voltage Out
Positive terminal to secondary charge-pump capacitor
Negative terminal to primary charge-pump capacitor
Input Supply
4
_______________________________________________________________________________________
High-Side Power Supply
MAX1822
V
OUT
S8
11V
8.5V
C3
V
INT
S7
C2
S6
S4
RC OSCILLATOR
+
CONTROL LOGIC
OVERVOLTAGE
COMPARATOR
POWER-READY
COMPARATOR
S3
V
CC
C1
S2
PR
PR DRIVER
S1
S5
GND
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 V
CC
up to four times, the output is regulated to V
CC
+ 11V by an internal feedback circuit for inputs above
4V. The charge pump typically operates at 90kHz, but
regulates by pulse skipping. When V
OUT
exceeds V
CC
+ 11V, the oscillator shuts off. As V
OUT
dips below V
CC
+ 11V, the oscillator turns on.
V
OUT
reaches approximately V
CC
+ 8.5V. PR also goes
low if V
OUT
falls below this level during operation, i.e., if
the output is overloaded. The PR high level is V
CC
.
Applications Information
Quiescent Supply Current
MAX1822 quiescent supply current varies with V
CC
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 V
OUT
. As V
CC
falls below 5V, quiescent
current rises fairly rapidly to about 1mA at 4V (Typical
Operating Characteristics).
This rise occurs because
V
OUT
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
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
_______________________________________________________________________________________
京公网安备 11010802033920号
EEWORLD
