19-1792; Rev 0; 9/00
SC70 Inverting Charge Pumps
with Shutdown
General Description
The MAX1852/MAX1853 monolithic, CMOS charge-
pump voltage inverters in the ultra-small SC70 package
feature a low 15Ω output resistance, permitting loads
up to 30mA with maximum efficiency. The MAX1852/
MAX1853 are available with operating frequencies of
50kHz and 200kHz, respectively, allowing optimization
of supply current or external component size. Small
external components and micropower shutdown mode
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. Applications include
generating a negative supply from a +5V or +3.3V logic
supply to power analog circuitry. Both versions come in
a 6-pin SC70 package that is 40% smaller than a
SOT23.
o
30mA Output Current
o
Low 15Ω Output Resistance
o
68µA Supply Current (MAX1852)
o
Requires Only Two 0.68µF Capacitors (MAX1853)
o
+2.5V to +5.5V Input Voltage Range
o
0.1µA Logic-Controlled Shutdown
o
Two Switching Frequencies
50kHz (MAX1852)
200kHz (MAX1853)
o
Slew-Rate Limited to Reduce EMI
o
Ultra-Small 6-Pin SC70 Package
Features
MAX1852/MAX1853
Applications
Negative Supply from +5V or +3.3V Logic Supplies
Small LCD Panels
GaAsFET Bias Supplies
Handy-Terminals, PDAs
Battery-Operated Equipment
PART
MAX1852EXT
MAX1853EXT
TEMP.
RANGE
-40°C to +85°C
-40°C to +85°C
PIN-
PACKAGE
6 SC70
6 SC70
TOP
MARK
AAL
AAM
Ordering Information
Typical Operating Circuit
0.68µF
Pin Configuration
TOP VIEW
INPUT
2.5V TO 5.5V
C1+
IN
C1-
OUT
NEGATIVE
OUTPUT
-1
✕
V
IN
30mA
0.68µF
OUT
1
6
C1+
MAX1853
ON
OFF
SHDN
GND
GND
2
MAX1852
MAX1853
5
C1-
SHDN
3
4
IN
SC70-6
________________________________________________________________
Maxim Integrated Products
1
For free samples and the latest literature, visit www.maxim-ic.com or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
SC70 Inverting Charge Pumps
with Shutdown
MAX1852/MAX1853
ABSOLUTE MAXIMUM RATINGS
IN to GND .................................................................-0.3V to +6V
C1+,
SHDN
to GND .....................................-0.3V to (V
IN
+ 0.3V)
C1- to GND...............................................(V
OUT
- 0.3V) to +0.3V
OUT to GND .............................................................+0.3V to -6V
OUT Short-Circuit to GND ..............................................1 minute
Continuous Power Dissipation (T
A
= +70°C)
6-Pin SC70 (derate 3.1mW/°C above +70°C) .............245mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°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
(Circuit of Figure 1, capacitors from Table 2, V
IN
= +5V,
SHDN
= IN, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are
at T
A
= +25°C.) (Note 1)
PARAMETER
Supply Voltage Range
MAX1852
Quiescent Supply Current
MAX1853
Shutdown Supply Current
SHDN
= GND
MAX1852
Oscillator Frequency
MAX1853
Voltage Conversion Efficiency
Output Resistance (Note 2)
Output Current
SHDN
Input Logic High
SHDN
Input Logic Low
SHDN
Bias Current
Wake-Up Time From Shutdown
I
OUT
= 0
I
OUT
= 10mA
Continuous, long-term
+2.5V
≤
V
IN
≤
+5.5V
+2.5V
≤
V
IN
≤
+5.5V
SHDN
= GND or IN
I
OUT
= 5mA
T
A
= +25°C
T
A
= +85°C
MAX1852
MAX1853
-100
1
10
260
112
0.7
×
V
IN
0.3
×
V
IN
100
T
A
= +25°C
T
A
= -40°C to +85°C
T
A
= +25°C
T
A
= -40°C to +85°C
T
A
= +25°C
T
A
= -40°C to +85°C
T
A
= +25°C
T
A
= +85°C
T
A
= +25°C
T
A
= -40°C to +85°C
T
A
= +25°C
T
A
= -40°C to +85°C
32
25
130
110
99
99.9
15
30
40
30
200
0.002
0.01
50
68
78
270
310
%
Ω
mA
RMS
V
V
nA
µs
kHz
165
CONDITIONS
MIN
2.5
75
TYP
MAX
5.5
130
150
320
350
0.5
µA
µA
UNITS
V
Note 1:
All devices are 100% production tested at T
A
= +25°C. All temperature limits are guaranteed by design.
Note 2:
Output resistance is guaranteed with capacitor ESR of 0.3Ω or less.
2
_______________________________________________________________________________________
SC70 Inverting Charge Pumps
with Shutdown
MAX1852/MAX1853
Typical Operating Characteristics
(Circuit of Figure 1, capacitors from Table 2, V
IN
= +5V,
SHDN
= IN, T
A
= +25°C, unless otherwise noted.)
MAX1852
OUTPUT VOLTAGE
vs. LOAD CURRENT
MAX1852/3 toc01
MAX1853
OUTPUT VOLTAGE
vs. LOAD CURRENT
MAX1852/3 toc02
MAX1852
EFFICIENCY vs. LOAD CURRENT
90
80
EFFICIENCY (%)
70
60
50
40
30
20
V
IN
= +5V
V
IN
= +3.3V
V
IN
= +2.5V
MAX1852/3 toc03
-2.0
-2.5
V
IN
= +3.3V
OUTPUT VOLTAGE (V)
-3.0
-3.5
-4.0
-4.5
-5.0
-5.5
0
5
10
15
20
25
V
IN
= +5V
-2.0
-2.5
V
IN
= +3.3V
OUTPUT VOLTAGE (V)
-3.0
-3.5
-4.0
-4.5
-5.0
-5.5
V
IN
= +5V
100
10
0
0
5
10
15
20
25
30
0
5
10
15
20
25
30
LOAD CURRENT (mA)
LOAD CURRENT (mA)
30
LOAD CURRENT (mA)
MAX1853
EFFICIENCY vs. LOAD CURRENT
MAX1852/3 toc04
OUTPUT RESISTANCE vs. INPUT VOLTAGE
22
OUTPUT RESISTANCE (Ω)
21
20
19
18
17
16
15
14
13
MAX1852
MAX1853
MAX1852/3 toc05
NO-LOAD SUPPLY CURRENT
vs. SUPPLY VOLTAGE
180
160
SUPPLY CURRENT (µA)
140
120
100
80
60
40
20
0
MAX1852
MAX1853
MAX1852/3 toc06
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0
5
10
15
20
25
V
IN
= +5V
V
IN
= +3.3V
V
IN
= +2.5V
23
200
30
2.5
3.0
3.5
4.0
4.5
5.0
5.5
0
1
2
3
4
5
LOAD CURRENT (mA)
INPUT VOLTAGE (V)
SUPPLY VOLTAGE (V)
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
MAX1852/3 toc07
MAX1852
OUTPUT RESISTANCE vs. TEMPERATURE
MAX1852/3 toc08
MAX1853
OUTPUT RESISTANCE vs. TEMPERATURE
26
OUTPUT RESISTANCE (Ω)
24
22
20
18
16
14
12
V
IN
= +5V
V
IN
= +3.3V
V
IN
= +2.5V
MAX1852/3 toc09
8
7
SUPPLY CURRENT (nA)
6
5
4
3
2
1
0
-40
-15
10
35
60
28
26
OUTPUT RESISTANCE (Ω)
24
V
IN
= +2.5V
22
20
18
16
14
12
-40
-15
10
35
60
V
IN
= +5V
V
IN
= +3.3V
28
85
85
-40
-15
10
35
60
85
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
_______________________________________________________________________________________
3
SC70 Inverting Charge Pumps
with Shutdown
MAX1852/MAX1853
Typical Operating Characteristics (continued)
(Circuit of Figure 1, capacitors from Table 2, V
IN
= +5V,
SHDN
= IN, T
A
= +25°C, unless otherwise noted.)
MAX1852
CHARGE-PUMP FREQUENCY
vs. TEMPERATURE
MAX1852/3 toc10
MAX1853
CHARGE-PUMP FREQUENCY
vs. TEMPERATURE
MAX1852/3 toc11
CHARGE-PUMP FREQUENCY
vs. INPUT VOLTAGE
270
220
170
120
70
20
MAX1852
MAX1853
MAX1852/3 toc12
60
59
58
FREQUENCY (kHz)
57
56
55
54
53
52
51
50
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
230
225
FREQUENCY (kHz)
220
215
210
205
200
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
FREQUENCY (kHz)
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
INPUT VOLTAGE (V)
MAX1852 AND MAX1853
OUTPUT VOLTAGE vs. INPUT VOLTAGE
MAX1852/3 toc13
OUTPUT VOLTAGE RIPPLE
vs. CAPACITANCE
MAX1852/3 toc14
MAX1852
OUTPUT NOISE AND RIPPLE
C1 = C2 = 4.7µF
MAX1852/3 toc15
-2.0
-2.5
OUTPUT VOLTAGE (V)
-3.0
-3.5
-4.0
-4.5
-5.0
-5.5
2.0
2.5
3.0
3.5
4.0
I
LOAD
= 10mA
350
OUTPUT VOLTAGE RIPPLE (mV)
300
250
200
150
100
MAX1853
50
0
MAX1852
C1 = C2
I
LOAD
= 10mA
V
OUT
20mV/div
4.5
5.0
5.5
0.2 0.7 1.2 1.7 2.2 2.7 3.2 3.7 4.2 4.7
CAPACITANCE (µF)
INPUT VOLTAGE (V)
10µs/div
I
LOAD
= 10mA, AC-COUPLED
MAX1853
OUTPUT NOISE AND RIPPLE
C1 = C2 = 1µF
MAX1852/3 toc16
MAX1852
STARTUP FROM SHUTDOWN
MAX1852/3 toc17
MAX1853
STARTUP FROM SHUTDOWN
MAX1852/3 toc18
SHDN
SHDN
V
OUT
20mV/div
0
0
2V/div
0
0
V
OUT
2V/div
V
OUT
2µs/div
I
LOAD
= 10mA, AC-COUPLED
100µs/div
40µs/div
4
_______________________________________________________________________________________
SC70 Inverting Charge Pumps
with Shutdown
Pin Description
C1
MAX1852/MAX1853
PIN
NAME
OUT
GND
SHDN
FUNCTION
Inverting Charge-Pump Output
Ground
Shutdown Input. Drive this pin high
for normal operation; drive it low for
shutdown mode.
Power-Supply Voltage Input. Input
range is +2.5V to +5.5V.
Negative Terminal of the Flying
Capacitor
Positive Terminal of the Flying
Capacitor
INPUT
2.5V TO 5.5V
C3
4
6
C1+
IN
5
C1-
OUT
1
R
L
NEGATIVE
OUTPUT
-1
✕
V
IN
C2
1
2
3
ON
OFF
3
MAX1852
MAX1853
SHDN
GND
2
4
5
6
IN
C1-
C1+
TE:
(
Figure 1. Typical Application Circuit
Detailed Description
The MAX1852/MAX1853 charge pumps invert the volt-
age applied to their input. For highest 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 V
IN
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
-V
IN
. The actual voltage at the output is more positive
than -V
IN
since switches S1–S4 have resistance and the
load drains charge from C2.
resistances (typically 6Ω at V
IN
= +5V). The typical out-
put impedance is more accurately determined from the
Typical Operating Characteristics.
Shutdown
The MAX1852/MAX1853 have a logic-controlled shut-
down input. Driving
SHDN
low places the devices in a
low-power shutdown mode. The charge-pump switch-
ing halts, supply current is reduced to 2nA.
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.
Applications Information
Capacitor Selection
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:
5
Efficiency Considerations
The efficiency of the MAX1852/MAX1853 is dominated
by their quiescent supply current (I
Q
) at low output cur-
rent and by their output impedance (R
OUT
) at higher
output current; it is given by:
I
OUT
I
OUT
x R
OUT
η≅
1
−
V
IN
I
OUT
+
I
Q
where the output impedance is roughly approximated
by:
1
R
OUT
≅
+
2R
SW
+
4ESR
C1
+
ESR
C2
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
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