19-1774; Rev 0; 7/00
KIT
ATION
EVALU
LE
B
A
IL
A
AV
High-Frequency, Regulated,
200mA, Inverting Charge Pump
Features
♦ 200mA Output Current
♦ Up to 2MHz Switching Frequency
♦ Small Capacitors (1µF)
♦ +2.7V to +5.5V Input Voltage Range
♦ Adjustable Regulated Negative Output
(-2.5V to -VIN)
♦ 0.1µA Logic-Controlled Shutdown
♦ Low 0.05Ω Output Resistance (in regulation)
♦ Soft-Start and Foldback Current Limited
♦ Short-Circuit and Thermal Shutdown Protected
♦ 8-Pin SO Package
________________________Applications
Ordering Information
TFT Panels
TEMP.
RANGE
PART
Hard Disk Drives
PINSWITCHING
PACKAGE FREQUENCY
Camcorders
MAX889TESA
-40°C to +85°C
8 SO
2MHz
Digital Cameras
MAX889SESA
-40°C to +85°C
8 SO
1MHz
Measurement Instruments
MAX889RESA
-40°C to +85°C
8 SO
0.5MHz
Battery-Powered Applications
Typical Operating Circuit
Pin Configuration
INPUT +2.7V TO +5.5V
TOP VIEW
ON
OFF
SHDN
IN
FB
CAP+ MAX889
OUT
CAPAGND
REGULATED
NEGATIVE
OUTPUT
(UP TO -1 × VIN,
UP TO 200mA)
IN
1
CAP+
2
8
AGND
7
FB
3
6
SHDN
CAP- 4
5
OUT
MAX889
GND
GND
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.
MAX889
General Description
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 -VIN.
The MAX889 is available with an operating frequency of
2MHz (T version), 1MHz (S version), or 0.5MHz (R version). The higher switching frequency devices allow the
use of smaller capacitors for space-limited applications. The lower frequency devices have lower quiescent current.
The MAX889 also features a 0.1µA logic-controlled
shutdown mode and is available in an 8-pin SO package. An evaluation kit, MAX889SEVKIT, is available.
MAX889
High-Frequency, Regulated,
200mA, Inverting Charge Pump
ABSOLUTE MAXIMUM RATINGS
IN to GND .................................................................-0.3V to +6V
FB, SHDN, CAP+ to GND ............................-0.3V to (VIN + 0.3V)
AGND to GND .......................................................-0.3V to +0.3V
OUT to GND .............................................................-6V to +0.3V
CAP- to GND ............................................(VOUT - 0.3V) to +0.3V
Continuous Output Current ...............................................250mA
Output Short-Circuit Duration ........................................Indefinite
Continuous Power Dissipation (TA = +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
(VIN = V SHDN = +5V, capacitors from Table 1, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
UNITS
Supply Voltage Range
VIN
RLOAD = 100Ω
2.7
5.5
V
Output Voltage Range
VOUT
R LOAD = 100Ω
-2.5
-VIN
V
VIN = 5V, VOUT = -3.3V
200
VIN = 3.3V, VOUT = -2.5V
145
Maximum Output Current
Quiescent Supply
Current (Free-Run Mode)
IOUT(MAX)1
IOUT(MAX)2
IQ(FREE-RUN)
No load, VFB = VIN
No load, VOUT regulated to
-3.3V
mA
MAX889R
6
12
MAX889S
12
24
MAX889T
24
48
MAX889R
3.3
7
MAX889S
5.5
12
mA
Quiescent Supply
Current (Regulated Mode)
IQ(REGULATED)
11
22
Shutdown Supply Current
I SHDN
V SHDN = 0
0.1
50
µA
RO
VFB = VIN
2.0
4.5
Ω
VOUT regulated to -3.3V
0.05
±1
µA
±35
mV
MAX889T
Open-Loop Output
Resistance (Free-Run Mode)
Output Resistance
RO(REG1)
SHDN, FB Input Bias Current
FB Input Offset Voltage
ILOAD = 0
±3
Load Regulation
IOUT = 0 to 200mA
10
IN Undervoltage Lockout
Threshold
VIN rising (30mV hysteresis)
SHDN Logic High
VIH
SHDN Logic Low
VIL
Switching Frequency
Thermal Shutdown Threshold
2
MAX
fOSC
VIN = +2.7V to +5.5V
2.3
Ω
mV
2.6
0.7 x VIN
MAX889R
0.375
0.5
0.3 x VIN
0.62
MAX889S
0.75
1
1.25
MAX889T
1.5
2
2.5
Junction temperature rising
(15°C hysteresis)
160
_______________________________________________________________________________________
mA
V
V
MHz
°C
High-Frequency, Regulated,
200mA, Inverting Charge Pump
(VIN = V SHDN = +5V, capacitors from Table 1, TA = -40°C to +85°C, unless otherwise noted.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
MAX
UNITS
Supply Voltage Range
VIN
RLOAD = 100Ω
2.7
5.5
V
Output Voltage Range
VOUT
R LOAD = 100Ω
-2.5
-VIN
V
IOUT(MAX)1
VIN = 5V, VOUT = -3.3V
200
IOUT(MAX)2
VIN = 3.3V, VOUT = -2.5V
145
Maximum Output Current
Quiescent Supply
Current (Free-Run Mode)
IQ(FREE-RUN)
No load, VFB = VIN
No load, VOUT regulated to
-3.3V
mA
MAX889R
12
MAX889S
24
MAX889T
48
MAX889R
7
MAX889S
12
mA
Quiescent Supply
Current (Regulated Mode)
IQ(REGULATED)
Shutdown Supply Current
I SHDN
V SHDN = 0
50
µA
RO
VFB = VIN
4.5
Ω
±1
µA
FB Input Offset Voltage
ILOAD = 0
±35
mV
IN Undervoltage Lockout
Threshold
VIN rising (30mV hysteresis)
2.6
V
MAX889T
Open-Loop Output
Resistance (Free-Run Mode)
22
SHDN FB Input Bias Current
SHDN Logic High
VIH
SHDN Logic Low
VIL
Switching Frequency
2.3
0.7 x V IN
VIN = +2.7V to +5.5V
fOSC
mA
MAX889R
0.375
0.3 x VIN
0.62
MAX889S
0.75
1.25
MAX889T
1.5
2.5
V
MHz
Note 1: Specifications to -40°C are guaranteed by design, not production tested.
Typical Operating Characteristics
(Circuit of Figure 1, VIN = V SHDN = +5V, capacitors from Table 1, TA = +25°C, unless otherwise noted.)
MAX889T
-3.28
MAX889S
-3.29
-3.30
-3.31
COUT = 10µF
COUT = 22µF
20
600
OUTPUT LOAD CURRENT (mA)
COUT = 10µF
20
COUT = 22µF
0
0
400
30
COUT = 47µF
-3.33
200
COUT = 4.7µF
10
MAX889R
0
MAX889 toc03
MAX889 toc02
30
10
-3.32
40
OUTPUT RIPPLE (mV)
-3.27
OUTPUT RIPPLE (mV)
-3.26
OUTPUT VOLTAGE (V)
40
MAX889 toc01
-3.25
MAX889S
OUTPUT RIPPLE
vs. LOAD CURRENT vs. COUT
MAX889R
OUTPUT RIPPLE
vs. LOAD CURRENT vs. COUT
OUTPUT VOLTAGE
vs. LOAD CURRENT
800
0
50
100
150
200
250
LOAD CURRENT (mA)
300
350
0
50
100
150
200
250
300
350
LOAD CURRENT (mA)
_______________________________________________________________________________________
3
MAX889
ELECTRICAL CHARACTERISTICS
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VIN = V SHDN = +5V, capacitors from Table 1, TA = +25°C, unless otherwise noted.)
30
COUT = 4.7µF
20
10
MAX889R
COUT = 10µF
0
70
60
50
MAX889T
MAX889S
40
90
50
100
150
200
250
300
70
60
40
30
20
20
10
10
350
MAX889T
MAX889S
50
30
0
0
0
100
200
300
400
0
500
50
100
150
200
350
FREE-RUN OUTPUT RESISTANCE
vs. INPUT VOLTAGE
FREE-RUN OUTPUT RESISTANCE
vs. TEMPERATURE
QUIESCENT SUPPLY CURRENT
vs. INPUT VOLTAGE (REGULATED MODE)
2.5
ROUT (Ω)
2.50
2.25
12
10
QUIESCENT CURRENT (mA)
MAX889 toc07
3.0
2.0
2.00
1.5
1.75
MAX889T
8
MAX889S
6
4
MAX889R
2
1.0
3.0
3.5
4.0
4.5
5.0
VOUT = -2.5V
0
-40
5.5
-20
0
20
40
60
80
2.5
TEMPERATURE (°C)
INPUT VOLTAGE (V)
4.0
0
A
A
A
B
B
B
0
C
40µs/div
20 TO 200mA LOAD STEP
CIRCUIT OF FIGURE 4
A: IOUT, 100mA/div
B: VOUT, 20mV/div, AC-COUPLED
40µs/div
IOUT = 200mA
CIRCUIT OF FIGURE 4
A: VIN, 2V/div
B: VOUT, 10mV/div, AC-COUPLED
4.5
5.0
5.5
MAX889S
STARTUP AND SHUTDOWN
MAX889 toc11
MAX889 toc10
3.5
INPUT VOLTAGE (V)
MAX889S
LINE-TRANSIENT RESPONSE
MAX889S
LOAD-TRANSIENT RESPONSE
3.0
MAX889 toc12
1.50
MAX889 toc09
LOAD CURRENT (mA)
2.75
4
300
LOAD CURRENT (mA)
3.00
2.5
250
LOAD CURRENT (mA)
MAX889 toc08
0
MAX889R
80
EFFICENCY (%)
EFFICIENCY (%)
COUT = 2.2µF
90
80
100
MAX889 toc05
40
OUTPUT RIPPLE (mV)
100
MAX889 toc04
50
EFFICIENCY vs. LOAD CURRENT
(VIN = 3.3V, VOUT = -2.5V)
EFFICIENCY vs. LOAD CURRENT
(VIN = 5V, VOUT = -3.3V)
MAX889 toc06
MAX889T
OUTPUT RIPPLE
vs. LOAD CURRENT vs. COUT
ROUT (Ω)
MAX889
High-Frequency, Regulated,
200mA, Inverting Charge Pump
2ms/div
IOUT = 200mA
A: VOUT, 1V/div
B: IIN, 100mA/div
C: VSHDN, 10V/div
_______________________________________________________________________________________
High-Frequency, Regulated,
200mA, Inverting Charge Pump
PIN
NAME
FUNCTION
1
IN
Power-Supply Positive Voltage Input
2
CAP+
Positive Terminal of Flying Capacitor
3
GND
Power Ground
4
CAP-
Negative Terminal of Flying Capacitor
5
OUT
Inverting Charge-Pump Output
6
SHDN
Shutdown Control Input. Drive SHDN low to shut down the MAX889. Connect SHDN to IN for
normal operation.
7
FB
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.
8
AGND
Analog Ground
Detailed Description
The MAX889 high-current regulated charge-pump DCDC inverter provides up to 200mA. It features the highest available output current while using small
capacitors (Table 1). The three versions available differ
in their switching frequencies (f OSC ) — MAX889R/
MAX889S/MAX889T with fOSC = 500kHz/1MHz/2MHz,
respectively. Higher frequencies allow the use of smaller 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 current. 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-circuit, 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 (CFLY) to the
input voltage (CAP- = GND, CAP+ = IN). During the
other half cycle, switches S3 and S4 close (Figure 3),
transferring the charge on CFLY to the output capacitor
(CAP+ = GND, CAP- = OUT).
Voltage Regulation
Voltage regulation is achieved by controlling the flyingcapacitor charging rate. The MAX889 controls the
charge on CFLY by modulating the gate drive to S1
(Figure 2) to supply the charge necessary to maintain
output regulation. When the output voltage droops,
CFLY charges higher due to increased gate drive. Since
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 supply voltage (VOUT = -(VIN - IOUT x RO)). Output resistance is typically 2Ω and can be approximated by the
following equation:
RO ≅ [1 / (fOSC x CFLY) ] + 2RSW +
4ESRCFLY + ESRCOUT
The first term is the effective resistance of an ideal
switched-capacitor circuit (Figures 2 and 3), and RSW
is the sum of the charge pump’s internal switch resistances (typically 0.8Ω at VIN = 5V). The last two terms
take into consideration the equivalent series resistance
_______________________________________________________________________________________
5
MAX889
Pin Description
MAX889
High-Frequency, Regulated,
200mA, Inverting Charge Pump
(ESR) of the flying and output capacitors. The typical
output impedance is more accurately determined from
the Typical Operating Characteristics.
pump switching halts. Connect SHDN to IN or drive
high for normal operation.
Current Limit and Soft-Start
The MAX889 features thermal shutdown with hysteresis
for added protection against fault conditions. When the
die temperature exceeds 160°C, the internal oscillator
stops, suspending device operation. The MAX889
resumes operation when the die temperature falls 15°C.
This prevents the device from rapidly oscillating around
the temperature trip point.
The MAX889 features a foldback current-limit/soft-start
scheme that allows it to limit inrush currents during
startup, overload, and output short-circuit conditions.
Additionally, it permits a safe, timed recovery from fault
conditions. This protects the MAX889 and prevents
low-current or higher output impedance input supplies
(such as alkaline cells) from being overloaded at startup or short-circuit conditions.
The MAX889 features two current-limit/soft-start levels
with corresponding response to rising and falling output voltage thresholds of -0.6V and -1.5V. When the
falling output voltage crosses -1.5V, such as during an
overload condition, the input current is immediately limited to 400mA by weakening the charge-pump switches. When the falling output voltage crosses -0.6V, such
as during a short-circuit condition, the MAX889 further
weakens the charge-pump switches, immediately limiting input current to 200mA.
During startup or short-circuit recovery, the MAX889
limits input current to 200mA with charge-pump switches at their weakest level. Rising output voltage crossing
-0.6V initiates a 2ms timer, after which the MAX889
increases switch strength to the next level. The rising
output voltage crossing -1.5V initiates a 2ms timer, after
which the MAX889 provides full-strength operation.
Thermal Shutdown
Applications Information
Resistor Selection
(Setting the Output Voltage)
The accuracy of VOUT depends on the accuracy of the
voltage biasing R1 in Figure 1. Use a separate reference voltage if greater accuracy than provided by VIN
is desired (Figure 4). Keep the feedback node as small
as possible, with resistors mounted close to the FB pin.
S1
CAP+
S3
IN
S2
CFLY
S4
COUT
OUT
CAPFOSC
Shutdown
When SHDN (a CMOS-compatible input) is driven low,
the MAX889 enters 0.1µA shutdown mode. Charge-
INPUT
5.0V
CIN
4.7µF
ON
6
SHDN
2
CFLY
1µF
R1
100k
1
OFF
IN
FB
S1
7
5
COUT
4.7µF
CAP-
CAP+
S3
IN
R1
66.5k
CAP+ MAX889T
OUT
4
Figure 2. Charging CFLY
S2
CFLY
S4
COUT
OUT
OUTPUT
-3.3V
CAPFOSC
GND
8
Figure 1. Typical Application Circuit.
6
3
Figure 3. Transferring Charge on CFLY to COUT
_______________________________________________________________________________________
High-Frequency, Regulated,
200mA, Inverting Charge Pump
Capacitor Selection
The appropriate capacitors used with the MAX889
depend on the switching frequency. Table 1 provides
suggested values for CIN, CFLY, and COUT.
Surface-mount ceramic capacitors are preferred for
CIN, COUT, and CFLY due to their small size, low cost,
and low ESR. To ensure proper operation over the
entire temperature range, choose ceramic capacitors
with X7R (or equivalent) low-temperature-coefficient
(tempco) dielectrics. See Table 2 for a list of suggested
capacitor suppliers.
The output capacitor stores the charge transferred from
the flying capacitor and services the load between
oscillator cycles. A good general rule is to make the
output capacitance at least five-times greater than the
flying capacitor.
Output voltage ripple is largely dependent on COUT.
Choosing a low-ESR capacitor of sufficient value is important in minimizing the peak-to-peak output voltage ripple,
which is approximated by the following equation:
IOUT
+
2 x fOSC COUT
2 x IOUT ESRCOUT
VRIPPLE =
where COUT is the output capacitor value, ESRCOUT is
the output capacitor’s ESR, and fOSC is the MAX889
switching frequency. Ceramic capacitors have the lowest
ESR and are recommended for COUT. Where larger
capacitance at low cost is desired, a low-ESR tantalum
capacitor may be used for COUT. See Table 2 for a list of
suggested capacitor suppliers.
To ensure stability over the entire operating temperature
range, choose a low-ESR output capacitor using the following equation:
15.5
R1
COUT ≥
fMIN R1 + R2
IOUT
where COUT is the output capacitor value, and fMIN is the
minimum oscillator frequency in the Electrical
Characteristics table.
To ensure stability for regulated output mode, suitable
output capacitor ESR should be determined by the following equation:
19.2 x 10-3
R2
RESR ≤
1 +
R1
IOUT
Power Dissipation
The power dissipated in the MAX889 depends on the
input voltage, output voltage, and output current. Device
power dissipation is accurately described by:
PDISS = IOUT (VIN - (-VOUT)) + (IQ ✕ VIN)
where IQ is the device quiescent current. PDISS must be
less than the package dissipation rating (see Absolute
Maximum Ratings). Pay particular attention to power dissipation limits when generating small negative voltages
from large positive input voltages.
Layout Considerations
The MAX889’s high oscillator frequencies demand
good layout techniques that ensure stability and help
maintain the output voltage under heavy loads. Take
the following steps to ensure optimum layout:
1) Mount all components as close together as possible.
2) Place the feedback resistors R1 and R2 close to the
FB pin, and minimize the PC trace length at the FB
circuit node.
3) Keep traces short to minimize parasitic inductance
and capacitance.
4) Use a ground plane with CIN and COUT placed in a
star ground configuration (see the MAX889SEVKIT
layout).
_______________________________________________________________________________________
7
MAX889
Adjust the output voltage to a negative voltage from
-2.5V to -V IN with external resistors R1 and R2 as
shown in Figures 1 and 4. FB servos to GND. Choose
R1 to be 100kΩ or less. Calculate R2 for the desired
output voltage:
VOUT = -VREF (R2 / R1)
R2 = R1 (VOUT / -VREF)
where VREF can be either VIN or a positive reference
source.
Typically, choose a voltage-divider current of at least
30µA to minimize the effect of FB input current and
capacitance:
R1 ≤ VREF / 30µA
R2 < -VOUT / 30µA
Table 1. Capacitor Selection Table
PART
FREQUENCY
CFLY
COUT
CIN
REGULATED
CIN
FREE-RUN
MAX889R
0.5MHz
4.7µF
22µF
22µF
4.7µF
MAX889S
1MHz
2.2µF
10µF
10µF
2.2µF
MAX889T
2MHz
1µF
4.7µF
4.7µF
1µF
Table 2. Low-ESR Capacitor Manufacturers
PRODUCTION
METHOD
MANUFACTURER
Surface-Mount
Tantalum
Surface-Mount Polymer
Surface-Mount Ceramic
SERIES
FAX
AVX
TPS series
803-946-0690
803-626-3123
Kemet
494 series
864-963-6300
864-963-6521
Matsuo
267 series
714-969-2491
714-960-6492
Sprague
593D, 595D series
603-224-1961
603-224-1430
Sanyo
POSCAP-APA
619-661-6835
619-661-1055
AVX
X7R
803-946-0690
803-626-3123
Kemet
X7R
864-963-6300
864-963-6521
Matsuo
X7R
714-969-2491
714-960-6492
Murata
GRM X7R
814-237-1431
814-238-0490
Chip Information
TRANSISTOR COUNT: 1840
PROCESS: BiCMOS
INPUT
5.0V
PHONE
Package Information
SOICN.EPS
MAX889
High-Frequency, Regulated,
200mA, Inverting Charge Pump
VREF
5V
CIN
4.7µF
ON
6
SHDN
OFF
2
CFLY
1µF
R1
100k
1
IN
FB
R2
66.5k
CAP+ MAX889T
OUT
4
7
5
CAPAGND
GND
8
COUT
4.7µF
OUTPUT
-3.3V
VOUT = -VREF × R2
R1
3
Figure 4. Separate VREF for Voltage Divider
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
8 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2000 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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