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.