View MAX889_133515.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

19-1774; Rev 0; 7/00
KIT ATION EVALU E AILABL AV
High-Frequency, Regulated, 200mA, Inverting Charge Pump
General Description Features
o 200mA Output Current o Up to 2MHz Switching Frequency o Small Capacitors (1F) o +2.7V to +5.5V Input Voltage Range o Adjustable Regulated Negative Output (-2.5V to -VIN) o 0.1A Logic-Controlled Shutdown o Low 0.05 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 -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 0.1A logic-controlled shutdown mode and is available in an 8-pin SO package. 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 -40C to +85C -40C to +85C -40C to +85C PINSWITCHING 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 CAPAGND GND
REGULATED NEGATIVE OUTPUT (UP TO -1 x VIN, 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 (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 = +70C) 8-Pin SO (derate 5.88mW/C above +70C)...............471mW Operating Temperature Range...........................-40C to +85C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) ................................+300C
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 = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER Supply Voltage Range Output Voltage Range Maximum Output Current Quiescent Supply Current (Free-Run Mode) SYMBOL VIN VOUT IOUT(MAX)1 IOUT(MAX)2 IQ(FREE-RUN) CONDITIONS RLOAD = 100 R LOAD = 100 VIN = 5V, VOUT = -3.3V VIN = 3.3V, VOUT = -2.5V MAX889R No load, VFB = VIN 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 VIH VIL fOSC ILOAD = 0 IOUT = 0 to 200mA VIN rising (30mV hysteresis) VIN = +2.7V to +5.5V MAX889R MAX889S MAX889T Thermal Shutdown Threshold Junction temperature rising (15C hysteresis) 2.3 0.7 x VIN 0.375 0.75 1.5 0.5 1 2 160 0.3 x VIN 0.62 1.25 2.5 C 3 10 2.6 IQ(REGULATED) I SHDN RO RO(REG1) No load, VOUT regulated to -3.3V V SHDN = 0 VFB = VIN VOUT 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 A A mV mV V V mA mA TYP MAX 5.5 -VIN UNITS V V mA
MHz
2
_______________________________________________________________________________________
High-Frequency, Regulated, 200mA, Inverting Charge Pump
ELECTRICAL CHARACTERISTICS
(VIN = V SHDN = +5V, capacitors from Table 1, TA = -40C to +85C, unless otherwise noted.) (Note 1)
PARAMETER Supply Voltage Range Output Voltage Range Maximum Output Current Quiescent Supply Current (Free-Run Mode) SYMBOL VIN VOUT IOUT(MAX)1 IOUT(MAX)2 IQ(FREE-RUN) CONDITIONS RLOAD = 100 R LOAD = 100 VIN = 5V, VOUT = -3.3V VIN = 3.3V, VOUT = -2.5V MAX889R No load, VFB = VIN 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 VIH VIL fOSC ILOAD = 0 VIN rising (30mV hysteresis) VIN = +2.7V to +5.5V MAX889R MAX889S MAX889T 2.3 0.7 x V IN 0.375 0.75 1.5 0.3 x VIN 0.62 1.25 2.5 IQ(REGULATED) I SHDN RO No load, VOUT regulated to -3.3V V SHDN = 0 VFB = VIN MAX889S MAX889T MIN 2.7 -2.5 200 145 12 24 48 7 12 22 50 4.5 1 35 2.6 A A mV V V mA mA MAX 5.5 -VIN UNITS V V mA
MAX889
MHz
Note 1: Specifications to -40C are guaranteed by design, not production tested.
Typical Operating Characteristics
(Circuit of Figure 1, VIN = V SHDN = +5V, capacitors from Table 1, TA = +25C, unless otherwise noted.)
OUTPUT VOLTAGE vs. LOAD CURRENT
MAX889 toc01
MAX889R OUTPUT RIPPLE vs. LOAD CURRENT vs. COUT
MAX889 toc02
MAX889S OUTPUT RIPPLE vs. LOAD CURRENT vs. COUT
COUT = 4.7F OUTPUT RIPPLE (mV) 30 COUT = 10F 20 COUT = 22F 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 COUT = 10F 20 COUT = 22F
10 COUT = 47F 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, VIN = V SHDN = +5V, capacitors from Table 1, TA = +25C, unless otherwise noted.)
MAX889T OUTPUT RIPPLE vs. LOAD CURRENT vs. COUT
MAX889 toc04
EFFICIENCY vs. LOAD CURRENT (VIN = 5V, VOUT = -3.3V)
90 80 EFFICIENCY (%) 70 60 50 40 30 MAX889S MAX889T MAX889R
MAX889 toc05
EFFICIENCY vs. LOAD CURRENT (VIN = 3.3V, VOUT = -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) COUT = 2.2F 30 COUT = 4.7F
20
10
COUT = 10F
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 ROUT ()
3.0
12 10 QUIESCENT CURRENT (mA) 8 6 4 2 MAX889R VOUT = -2.5V 2.5 3.0 3.5 4.0 4.5 5.0 MAX889S MAX889T
2.5 ROUT ()
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
_______________________________________________________________________________________
40s/div 20 TO 200mA LOAD STEP CIRCUIT OF FIGURE 4 A: IOUT, 100mA/div B: VOUT, 20mV/div, AC-COUPLED
40s/div IOUT = 200mA CIRCUIT OF FIGURE 4 A: VIN, 2V/div B: VOUT, 10mV/div, AC-COUPLED
2ms/div IOUT = 200mA A: VOUT, 1V/div B: IIN, 100mA/div C: VSHDN, 10V/div
High-Frequency, Regulated, 200mA, Inverting Charge Pump
Pin Description
PIN 1 2 3 4 5 6 7 8 NAME IN CAP+ GND CAPOUT 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 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).
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 0.05. 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 2 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 0.8 at VIN = 5V). The last two terms take into consideration the equivalent series resistance
5
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
_______________________________________________________________________________________
High-Frequency, Regulated, 200mA, Inverting Charge Pump MAX889
(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.
Thermal Shutdown
The MAX889 features thermal shutdown with hysteresis for added protection against fault conditions. When the die temperature exceeds 160C, the internal oscillator stops, suspending device operation. The MAX889 resumes operation when the die temperature falls 15C. This prevents the device from rapidly oscillating around the temperature trip point.
Current Limit and Soft-Start
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.
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 IN S2 CFLY
CAP+
S3 COUT OUT
S4 CAP-
FOSC
Shutdown
When SHDN (a CMOS-compatible input) is driven low, the MAX889 enters 0.1A shutdown mode. ChargeFigure 2. Charging CFLY
INPUT 5.0V
CIN 4.7F ON 6 2 CFLY 1F SHDN
1 IN FB 7
R1 100k S1 IN R1 66.5k OUT 5 COUT 4.7F GND OUTPUT -3.3V FOSC S2 CFLY CAPS4 COUT OUT CAP+ S3
OFF
CAP+ MAX889T
4
CAP-
8
3
Figure 1. Typical Application Circuit.
Figure 3. Transferring Charge on CFLY to COUT
6
_______________________________________________________________________________________
High-Frequency, Regulated, 200mA, Inverting Charge Pump
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 100k 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 30A to minimize the effect of FB input current and capacitance: R1 VREF / 30A R2 < -VOUT / 30A
MAX889
15.5 R1 COUT R1 + R2 fMIN
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
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:
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
High-Frequency, Regulated, 200mA, Inverting Charge Pump MAX889
Table 1. Capacitor Selection Table
PART MAX889R MAX889S MAX889T FREQUENCY 0.5MHz 1MHz 2MHz CFLY 4.7F 2.2F 1F COUT 22F 10F 4.7F CIN REGULATED 22F 10F 4.7F CIN FREE-RUN 4.7F 2.2F 1F
Table 2. Low-ESR Capacitor Manufacturers
PRODUCTION METHOD MANUFACTURER AVX Surface-Mount Tantalum Surface-Mount Polymer Kemet Matsuo Sprague Sanyo AVX Surface-Mount Ceramic Kemet Matsuo Murata SERIES TPS series 494 series 267 series 593D, 595D series POSCAP-APA X7R X7R X7R GRM X7R PHONE 803-946-0690 864-963-6300 714-969-2491 603-224-1961 619-661-6835 803-946-0690 864-963-6300 714-969-2491 814-237-1431 FAX 803-626-3123 864-963-6521 714-960-6492 603-224-1430 619-661-1055 803-626-3123 864-963-6521 714-960-6492 814-238-0490
Chip Information
TRANSISTOR COUNT: 1840 PROCESS: BiCMOS
Package Information
SOICN.EPS
INPUT 5.0V
VREF 5V CIN 4.7F ON 6 2 CFLY 1F SHDN R1 100k FB 7 R2 66.5k OUT 4 CAPAGND 8 GND 3 5 COUT 4.7F OUTPUT -3.3V VOUT = -VREF x R2 R1
1 IN
OFF
CAP+ MAX889T
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 (c) 2000 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

▲Up To Search▲

Price & Availability of MAX889

	To Download MAX889 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .