19-1774; Rev 0; 7/00
KIT
ATION
EVALU
BLE
AVAILA
High-Frequency, Regulated,
200mA, Inverting Charge Pump
General Description
Features
o
200mA Output Current
o
Up to 2MHz Switching Frequency
o
Small Capacitors (1µF)
o
+2.7V to +5.5V Input Voltage Range
o
Adjustable Regulated Negative Output
(-2.5V to -V
IN
)
o
0.1µA Logic-Controlled Shutdown
o
Low 0.05Ω Output Resistance (in regulation)
o
Soft-Start and Foldback Current Limited
o
Short-Circuit and Thermal Shutdown Protected
o
8-Pin SO Package
MAX889
The MAX889 inverting charge pump delivers a regulated
negative output voltage at loads of up to 200mA. The
device operates with inputs from 2.7V to 5.5V to produce
an adjustable, regulated output from -2.5V to -V
IN
.
The MAX889 is available with an operating frequency of
2MHz (T version), 1MHz (S version), or 0.5MHz (R ver-
sion). The higher switching frequency devices allow the
use of smaller capacitors for space-limited applica-
tions. The lower frequency devices have lower quies-
cent current.
The MAX889 also features a 0.1µA logic-controlled
shutdown mode and is available in an 8-pin SO pack-
age. An evaluation kit, MAX889SEVKIT, is available.
________________________Applications
TFT Panels
Hard Disk Drives
Camcorders
Digital Cameras
Measurement Instruments
Battery-Powered Applications
PART
MAX889TESA
MAX889SESA
MAX889RESA
Ordering Information
TEMP.
RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-
SWITCHING
PACKAGE FREQUENCY
8 SO
8 SO
8 SO
2MHz
1MHz
0.5MHz
Typical Operating Circuit
INPUT +2.7V TO +5.5V
Pin Configuration
TOP VIEW
ON
OFF
SHDN
IN
FB
CAP+
MAX889
OUT
CAP-
AGND
GND
REGULATED
NEGATIVE
OUTPUT
(UP TO -1
×
V
IN
,
UP TO 200mA)
IN
CAP+
GND
1
2
8
7
AGND
FB
SHDN
OUT
MAX889
3
6
5
CAP-
4
SO
________________________________________________________________
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.
High-Frequency, Regulated,
200mA, Inverting Charge Pump
MAX889
ABSOLUTE MAXIMUM RATINGS
IN to GND .................................................................-0.3V to +6V
FB,
SHDN,
CAP+ to GND ............................-0.3V to (V
IN
+ 0.3V)
AGND to GND .......................................................-0.3V to +0.3V
OUT to GND .............................................................-6V to +0.3V
CAP- to GND ............................................(V
OUT
- 0.3V) to +0.3V
Continuous Output Current ...............................................250mA
Output Short-Circuit Duration ........................................Indefinite
Continuous 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
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°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
IN
= V
SHDN
= +5V, capacitors from Table 1,
T
A
=
0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
Supply Voltage Range
Output Voltage Range
Maximum Output Current
Quiescent Supply
Current (Free-Run Mode)
SYMBOL
V
IN
V
OUT
I
OUT(MAX)1
I
OUT(MAX)2
I
Q(FREE-RUN)
CONDITIONS
R
LOAD
= 100Ω
R
LOAD
= 100Ω
V
IN
= 5V, V
OUT
= -3.3V
V
IN
= 3.3V, V
OUT
= -2.5V
MAX889R
No load, V
FB =
V
IN
MAX889S
MAX889T
MAX889R
Quiescent Supply
Current (Regulated Mode)
Shutdown Supply Current
Open-Loop Output
Resistance (Free-Run Mode)
Output Resistance
SHDN,
FB Input Bias Current
FB Input Offset Voltage
Load Regulation
IN Undervoltage Lockout
Threshold
SHDN
Logic High
SHDN
Logic Low
Switching Frequency
V
IH
V
IL
f
OSC
I
LOAD
= 0
I
OUT
= 0 to 200mA
V
IN
rising (30mV hysteresis)
V
IN
= +2.7V to +5.5V
MAX889R
MAX889S
MAX889T
Thermal Shutdown Threshold
Junction temperature rising
(15°C hysteresis)
2.3
0.7 x V
IN
0.3 x V
IN
0.375
0.75
1.5
0.5
1
2
160
0.62
1.25
2.5
°C
MHz
±3
10
2.6
I
Q(REGULATED)
I
SHDN
R
O
R
O(REG1)
No load, V
OUT
regulated to
-3.3V
V
SHDN
= 0
V
FB
= V
IN
V
OUT
regulated to -3.3V
MAX889S
MAX889T
MIN
2.7
-2.5
200
145
6
12
24
3.3
5.5
11
0.1
2.0
0.05
±1
±35
12
24
48
7
12
22
50
4.5
µA
Ω
Ω
µA
mV
mV
V
V
mA
mA
TYP
MAX
5.5
-V
IN
UNITS
V
V
mA
2
_______________________________________________________________________________________
High-Frequency, Regulated,
200mA, Inverting Charge Pump
ELECTRICAL CHARACTERISTICS
(V
IN
= V
SHDN
= +5V, capacitors from Table 1,
T
A
=
-40°C to +85°C,
unless otherwise noted.) (Note 1)
PARAMETER
Supply Voltage Range
Output Voltage Range
Maximum Output Current
Quiescent Supply
Current (Free-Run Mode)
SYMBOL
V
IN
V
OUT
I
OUT(MAX)1
I
OUT(MAX)2
I
Q(FREE-RUN)
CONDITIONS
R
LOAD
= 100Ω
R
LOAD
= 100Ω
V
IN
= 5V, V
OUT
= -3.3V
V
IN
= 3.3V, V
OUT
= -2.5V
MAX889R
No load, V
FB =
V
IN
MAX889S
MAX889T
MAX889R
Quiescent Supply
Current (Regulated Mode)
Shutdown Supply Current
Open-Loop Output
Resistance (Free-Run Mode)
SHDN
FB Input Bias Current
FB Input Offset Voltage
IN Undervoltage Lockout
Threshold
SHDN
Logic High
SHDN
Logic Low
Switching Frequency
V
IH
V
IL
f
OSC
I
LOAD
= 0
V
IN
rising (30mV hysteresis)
V
IN
= +2.7V to +5.5V
MAX889R
MAX889S
MAX889T
2.3
0.7 x V
IN
0.375
0.75
1.5
0.3 x V
IN
0.62
1.25
2.5
I
Q(REGULATED)
I
SHDN
R
O
No load, V
OUT
regulated to
-3.3V
V
SHDN
= 0
V
FB
= V
IN
MAX889S
MAX889T
MIN
2.7
-2.5
200
145
12
24
48
7
12
22
50
4.5
±1
±35
2.6
µA
Ω
µA
mV
V
V
mA
mA
MAX
5.5
-V
IN
UNITS
V
V
mA
MAX889
MHz
Note 1:
Specifications to -40°C are guaranteed by design, not production tested.
Typical Operating Characteristics
(Circuit of Figure 1, V
IN
= V
SHDN
= +5V, capacitors from Table 1, T
A
= +25°C, unless otherwise noted.)
OUTPUT VOLTAGE
vs. LOAD CURRENT
MAX889 toc01
MAX889R
OUTPUT RIPPLE
vs. LOAD CURRENT vs. C
OUT
MAX889 toc02
MAX889S
OUTPUT RIPPLE
vs. LOAD CURRENT vs. C
OUT
C
OUT
= 4.7µF
OUTPUT RIPPLE (mV)
30
C
OUT
= 10µF
20
C
OUT
= 22µF
10
MAX889 toc03
-3.25
-3.26
OUTPUT VOLTAGE (V)
-3.27
-3.28
-3.29
-3.30
-3.31
-3.32
-3.33
0
200
400
600
MAX889R
MAX889T
MAX889S
40
40
OUTPUT RIPPLE (mV)
30
C
OUT
= 10µF
20
C
OUT
= 22µF
10
C
OUT
= 47µF
0
800
0
50
100
150
200
250
300
350
OUTPUT LOAD CURRENT (mA)
LOAD CURRENT (mA)
0
0
50
100
150
200
250
300
350
LOAD CURRENT (mA)
_______________________________________________________________________________________
3
High-Frequency, Regulated,
200mA, Inverting Charge Pump
MAX889
Typical Operating Characteristics (continued)
(Circuit of Figure 1, V
IN
= V
SHDN
= +5V, capacitors from Table 1, T
A
= +25°C, unless otherwise noted.)
MAX889T
OUTPUT RIPPLE
vs. LOAD CURRENT vs. C
OUT
MAX889 toc04
EFFICIENCY vs. LOAD CURRENT
(V
IN
= 5V, V
OUT
= -3.3V)
90
80
EFFICIENCY (%)
70
60
50
40
30
MAX889S
MAX889T
MAX889R
MAX889 toc05
EFFICIENCY vs. LOAD CURRENT
(V
IN
= 3.3V, V
OUT
= -2.5V)
90
80
EFFICENCY (%)
70
60
50
40
30
20
10
0
MAX889S
MAX889T
MAX889 toc06
50
100
100
MAX889R
40
OUTPUT RIPPLE (mV)
C
OUT
= 2.2µF
30
C
OUT
= 4.7µF
20
10
C
OUT
= 10µF
20
10
0
0
50
100
150
200
250
300
350
LOAD CURRENT (mA)
0
0
100
200
300
400
500
LOAD CURRENT (mA)
0
50
100
150
200
250
300
350
LOAD CURRENT (mA)
FREE-RUN OUTPUT RESISTANCE
vs. INPUT VOLTAGE
MAX889 toc07
FREE-RUN OUTPUT RESISTANCE
vs. TEMPERATURE
MAX889 toc08
QUIESCENT SUPPLY CURRENT
vs. INPUT VOLTAGE (REGULATED MODE)
MAX889 toc09
3.00
2.75
2.50
R
OUT
(Ω)
3.0
12
10
QUIESCENT CURRENT (mA)
8
6
4
2
MAX889R
V
OUT
= -2.5V
2.5
3.0
3.5
4.0
4.5
5.0
MAX889S
MAX889T
2.5
R
OUT
(Ω)
2.25
2.00
2.0
1.5
1.75
1.50
2.5
3.0
3.5
4.0
4.5
5.0
5.5
INPUT VOLTAGE (V)
1.0
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
0
5.5
INPUT VOLTAGE (V)
MAX889S
LOAD-TRANSIENT RESPONSE
MAX889 toc10
MAX889S
LINE-TRANSIENT RESPONSE
MAX889 toc11
MAX889S
STARTUP AND SHUTDOWN
0
MAX889 toc12
A
A
A
B
B
B
0
C
4
_______________________________________________________________________________________
40µs/div
20 TO 200mA LOAD STEP
CIRCUIT OF FIGURE 4
A: I
OUT
, 100mA/div
B: V
OUT
, 20mV/div, AC-COUPLED
40µs/div
I
OUT
= 200mA
CIRCUIT OF FIGURE 4
A: V
IN
, 2V/div
B: V
OUT
, 10mV/div, AC-COUPLED
I
OUT
= 200mA
A: V
OUT
, 1V/div
B: I
IN
, 100mA/div
C: V
SHDN
, 10V/div
2ms/div
High-Frequency, Regulated,
200mA, Inverting Charge Pump
Pin Description
PIN
1
2
3
4
5
6
7
8
NAME
IN
CAP+
GND
CAP-
OUT
SHDN
FB
AGND
Power-Supply Positive Voltage Input
Positive Terminal of Flying Capacitor
Power Ground
Negative Terminal of Flying Capacitor
Inverting Charge-Pump Output
Shutdown Control Input. Drive
SHDN
low to shut down the MAX889. Connect
SHDN
to IN for
normal operation.
Feedback Input. Connect FB to a resistor-divider from IN (or other positive reference voltage
source) to OUT for regulated output voltages. Connect to IN for free-run mode.
Analog Ground
FUNCTION
MAX889
Detailed Description
The MAX889 high-current regulated charge-pump DC-
DC inverter provides up to 200mA. It features the high-
est available output current while using small
capacitors (Table 1). The three versions available differ
in their switching frequencies (f
OSC
) — MAX889R/
MAX889S/MAX889T with f
OSC
= 500kHz/1MHz/2MHz,
respectively. Higher frequencies allow the use of small-
er components (Table 1). Even smaller capacitor values
than those listed in Table 1 are suitable when the
devices are loaded at less than their rated output cur-
rent. Designed specifically for compact applications, a
complete regulating circuit requires only three small
capacitors and two resistors, Figure 1. In addition, the
MAX889 includes soft-start, shutdown control, short-cir-
cuit, and thermal protection.
The oscillator, control circuitry, and four power MOSFET
switches are included on-chip. The charge pump runs
continuously at the operating frequency. During one-half
of the oscillator period, switches S1 and S2 close
(Figure 2), charging the transfer capacitor (C
FLY
) to the
input voltage (CAP- = GND, CAP+ = IN). During the
other half cycle, switches S3 and S4 close (Figure 3),
transferring the charge on C
FLY
to the output capacitor
(CAP+ = GND, CAP- = OUT).
the device switches continuously, the regulation
scheme minimizes output ripple, and the output noise
spectrum contains well-defined frequency components.
Feedback voltage is sensed with a resistor-divider
between an externally supplied positive reference or
the supply voltage and the negative inverted output.
The feedback loop servos FB to GND. The effective
output impedance in regulation is 0.05Ω. The output
remains in regulation until dropout is reached. Dropout
depends on the output voltage setting and load current
(see Output Voltage vs. Load Current in
Typical
Operating Characteristics).
Free-Run Mode
(Unregulated Voltage Inverter)
The MAX889 may be used in an unregulated voltage
inverter mode that does not require external feedback
resistors, minimizing board space. Connecting FB to IN
places the MAX889 in free-run mode. In this mode, the
charge pump operates to invert directly the input sup-
ply voltage (V
OUT
= -(V
IN
- I
OUT
x R
O
)). Output resis-
tance is typically 2Ω and can be approximated by the
following equation:
R
O
≅
[1 / (f
OSC
x C
FLY
) ] + 2R
SW
+
4ESR
CFLY
+ ESR
COUT
The first term is the effective resistance of an ideal
switched-capacitor circuit (Figures 2 and 3), and R
SW
is the sum of the charge pump’s internal switch resis-
tances (typically 0.8Ω at V
IN
= 5V). The last two terms
take into consideration the equivalent series resistance
5
Voltage Regulation
Voltage regulation is achieved by controlling the flying-
capacitor charging rate. The MAX889 controls the
charge on C
FLY
by modulating the gate drive to S1
(Figure 2) to supply the charge necessary to maintain
output regulation. When the output voltage droops,
C
FLY
charges higher due to increased gate drive. Since
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