19-0211; Rev 4; 5/96 NUAL KIT MA ATION SHEET A EVALU T A D WS FOLLO 3.3V/5V or Adjustable-Output, Step-Up DC-DC Converters ________________________Applications 3.3V to 5V Step-Up Conversion Palmtop Computers Portable Data-Collection Equipment Personal Data Communicators/Computers Medical Instrumentation 2-Cell & 3-Cell Battery-Operated Equipment Glucose Meters __________Typical Operating Circuit ____________________________Features ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ 0.8V to 6.0V Input Supply Voltage 0.8V Typ Start-Up Supply Voltage 85% Efficiency at 100mA 25µA Quiescent Current 1µA Shutdown Mode 125mA and 500mA Switch-Current Limits Permit Use of Low-Cost Inductors Up to 500kHz Switching Frequency ±1.5% Reference Tolerance Over Temperature Low-Battery Detector (LBI/LBO) 8-Pin SO and µMAX Packages ______________Ordering Information PART TEMP. RANGE MAX856CSA 0°C to +70°C MAX856CUA MAX856C/D MAX856ESA MAX856MJA MAX857CSA MAX857CUA MAX857C/D MAX857ESA MAX857MJA 0°C to +70°C 0°C to +70°C -40°C to +85°C -55°C to +125°C 0°C to +70°C 0°C to +70°C 0°C to +70°C -40°C to +85°C -55°C to +125°C PIN-PACKAGE 8 SO 8 µMAX Dice* 8 SO 8 CERDIP† 8 SO 8 µMAX Dice* 8 SO 8 CERDIP† Ordering Information continued at end of data sheet. * Dice are tested at TA = +25°C only. † Contact factory for availability. __________________Pin Configuration INPUT 0.8V TO VOUT TOP VIEW 47µH ON/OFF SHDN OUTPUT 5V AT 100mA OR 3.3V AT 125mA LX 1N5817 68µF SHDN 1 8 LX 3/5 2 7 GND 6 OUT 5 LBI REF 3 LBO 4 MAX856 3V/5V SELECT LOW-BATTERY DETECTOR INPUT 3/5 SO/µMAX OUT LBI REF GND LBO MAX856 MAX858 LOW-BATTERY DETECTOR OUTPUT SHDN 1 8 LX FB 2 7 GND 6 OUT 5 LBI REF 3 MAX857 MAX859 LBO 4 SO/µMAX ________________________________________________________________ Maxim Integrated Products 1 For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800 MAX856–MAX859 _______________General Description The MAX856–MAX859 are high-efficiency, CMOS, stepup, DC-DC switching regulators for small, low input voltage or battery-powered systems. The MAX856/MAX858 accept a positive input voltage between 0.8V and VOUT and convert it to a higher, pin-selectable output voltage of 3.3V or 5V. The MAX857/MAX859 adjustable versions accept 0.8V to 6.0V input voltages and generate higher adjustable output voltages in the 2.7V to 6.0V range. Typical efficiencies are greater than 85%. Typical quiescent supply current is 25µA (1µA in shutdown). The MAX856–MAX859 combine ultra-low quiescent supply current and high efficiency to give maximum battery life. An internal MOSFET power transistor permits high switching frequencies. This benefit, combined with internally set peak inductor current limits, permits the use of small, low-cost inductors. The MAX856/MAX857 have a 500mA peak inductor current limit. The MAX858/MAX859 have a 125mA peak inductor current limit. MAX856–MAX859 3.3V/5V or Adjustable-Output, Step-Up DC-DC Converters ABSOLUTE MAXIMUM RATINGS Supply Voltage (OUT to GND) ...................................-0.3V, +7V Switch Voltage (LX to GND) .......................................-0.3V, +7V ———– SHDN , LBO to GND ....................................................-0.3V, +7V –– LBI, REF, 3/ 5, FB to GND .........................-0.3V, (VOUT + 0.3V) Reference Current (IREF) ..................................................2.5mA Continuous Power Dissipation (TA = +70°C) SO (derate 5.88mW/°C above +70°C) .........................471mW µMAX (derate 4.1mW/°C above +70°C) ......................330mW CERDIP (derate 8.00mW/°C above +70°C) .................640mW Reverse Battery Current (TA ≤ +45°C, Note 1) .................750mA Operating Temperature Ranges MAX85_C_ _ ......................................................0°C to +70°C MAX85_E_ _ ....................................................-40°C to +85°C MAX85_MJA .................................................-55°C to +125°C Junction Temperature .....................................................+150°C Storage Temperature Range ............................-65°C to +160°C Lead Temperature (soldering, 10sec) ............................+300°C Note 1: Reverse battery current is measured from the Typical Operating Circuit’s battery input terminal to GND when the battery is connected backwards. A reverse current of 750mA will not exceed the SO or CERDIP package dissipation limits but, if left for an extended time (more than ten minutes), may degrade performance. 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 (Circuits of Figure 2, VIN = 2.5V, ILOAD = 0mA, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER Output Voltage Minimum Start-Up Supply Voltage CONDITIONS –– MAX856, 3/ 5 = 0V, 0mA ≤ ILOAD ≤ 100mA –– MAX856, 3/ 5 = 3V, 0mA ≤ ILOAD ≤ 150mA 2V ≤ VIN ≤ 3V MIN TYP MAX UNITS 4.80 5.0 5.20 3.17 3.3 3.43 MAX857, VOUT = 5V, 0mA ≤ ILOAD ≤100mA –– MAX858, 3/ 5 = 0V, 0mA ≤ ILOAD ≤ 25mA –– MAX858, 3/ 5 = 3V, 0mA ≤ ILOAD ≤ 35mA 4.80 5.0 5.20 4.80 5.0 5.20 3.17 3.3 3.43 MAX859, VOUT = 5V, 0mA ≤ ILOAD ≤ 25mA 4.80 5.0 5.20 0.8 1.8 ILOAD = 0mA Minimum Operating Voltage 0.8 Quiescent Supply Current in 3.3V Mode (Note 2) –– ILOAD = 0mA, 3/ 5 = 3V, LBI = 1.5V, VOUT = 3.47V, (FB = 1.5V, MAX857/MAX859 only) 25 No Load Battery Current Output set for 3.3V, measured at VIN in Figure 2, R3 omitted. 60 Shutdown Quiescent Current (Note 2) ———– –– SHDN = 0V, 3/ 5 = 3V, LBI = 1.5V, VOUT = 3.47V, (FB = 1.5V, MAX857/MAX859 only) 1 Peak Inductor Current Limit MAX85_C MAX856/MAX857 500 MAX858/MAX859 125 Reference Voltage No REF load –– Reference-Voltage Regulation 3/ 5 = 3V, -20µA ≤ REF load ≤ 250µA, CREF = 0.22µF 1.23 LBI Input Threshold 1.22 With falling edge LBI Input Hysteresis ISINK = 2mA LBO Output Leakage Current LBO = 5V 2 60 _______________________________________________________________________________________ µA µA 5 µA mA 1.25 1.27 V 0.8 2.0 % 1.25 1.28 V 25 LBO Output Voltage Low V V 1 MAX85_E/M V mV 0.4 V 1 µA 3.3V/5V or Adjustable-Output, Step-Up DC-DC Converters (Circuits of Figure 2, VIN = 2.5V, ILOAD = 0mA, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) –———– –– SHDN , 3/ 5 Input Voltage Low ———– –– SHDN , 3/ 5 Input Voltage High ———– –– SHDN , 3/ 5, FB, LBI Input Current –———– –– LBI = 1.5V, FB = 1.5V, SHDN = 0V or 3V, 3/ 5 = 0V or 3V FB Voltage MAX857/MAX859 1.22 Output Voltage Range MAX857/MAX859, ILOAD = 0mA (Note 3) 2.7 0.4 V ±100 nA 1.28 V 6.0 V 1.6 V 1.25 Note 2: Supply current from the 3.3V output is measured with an ammeter between the 3.3V output and OUT pin. This current correlates directly with actual battery supply current, but is reduced in value according to the step-up ratio and efficiency. VOUT = 3.47V to keep the internal switch open when measuring the current into the device. Note 3: Minimum value is production tested. Maximum value is guaranteed by design and is not production tested. __________________________________________Typical Operating Characteristics (Circuits of Figure 2, TA = +25°C, unless otherwise noted.) MAX858/MAX859 EFFICIENCY vs. OUTPUT CURRENT VOUT = 5V MAX858/MAX859 EFFICIENCY vs. OUTPUT CURRENT VOUT = 3.3V VIN = 2.5V 100 90 70 EFFICIENCY (%) VIN = 2.0V VIN = 1.5V 60 50 40 70 60 VIN = 1.5V VIN = 2.5V 50 40 30 30 20 20 10 10 0 0 0.001 0.01 1 0.1 100 10 LOAD CURRENT (mA) 0.001 1000 1 0.1 100 10 LOAD CURRENT (mA) 1000 MAX856/MAX857 EFFICIENCY vs. OUTPUT CURRENT VOUT = 3.3V MAX856/MAX857 EFFICIENCY vs. OUTPUT CURRENT VOUT = 5V 100 MAX856-03 100 VIN = 3.3V 90 0.01 90 VIN = 2.5V MAX856-04 EFFICIENCY (%) VIN = 3.3V 80 80 80 70 VIN = 2.0V 60 50 40 VIN = 1.5V 30 EFFICIENCY (%) 80 EFFICIENCY (%) MAX856-02 90 MAX856-01 100 70 VIN = 1.5V 60 50 VIN = 2.0V 40 30 20 20 10 10 0 0 0.001 0.01 100 1 0.1 10 LOAD CURRENT (mA) 1000 0.001 0.01 100 1 0.1 10 LOAD CURRENT (mA) 1000 _______________________________________________________________________________________ 3 MAX856–MAX859 ELECTRICAL CHARACTERISTICS (continued) _____________________________Typical Operating Characteristics (continued) (Circuits of Figure 2, TA = +25°C, unless otherwise noted.) MAX856/MAX857 NO LOAD BATTERY CURRENT vs. INPUT VOLTAGE 7 6 5 4 3 2 200 100 1.0 0.8 0.6 0.4 3.5 3.0 3.0 3.5 TA = +25°C TA = -40°C 1.5 1.05 VOUT = 3.3V 0.95 0.90 0.85 3.5 1.4 0.80 1.3 1.2 VOUT = 5V 1.1 1.0 0.9 10 1 100 0.1 10 1 100 INPUT VOLTAGE (V) LOAD CURRENT (mA) LOAD CURRENT (mA) SHUTDOWN CURRENT vs. INPUT VOLTAGE MAX856/MAX857 MAXIMUM OUTPUT CURRENT vs. INPUT VOLTAGE MAX858/MAX859 MAXIMUM OUTPUT CURRENT vs. INPUT VOLTAGE 0.9 350 100 MAX856-12 400 MAX856-11 1.0 4.0 0.8 0.1 4.0 3.0 MAX856-07 1.10 1.00 2.5 2.0 MAX858/MAX859 MINIMUM START-UP INPUT VOLTAGE vs. LOAD CURRENT 0.75 2.5 0.4 INPUT VOLTAGE (V) VOUT = 5V TA = -40°C 2.0 0.6 4.0 1.15 TA = +85°C 1.5 2.5 2.0 START-UP INPUT VOLTAGE (V) 1.2 0.2 0.8 MAX856/MAX857 MINIMUM START-UP INPUT VOLTAGE vs. LOAD CURRENT START-UP INPUT VOLTAGE (V) SEE NOTE 2 IN THE ELECTRICAL CHARACTERISTICS 1.4 1.0 INPUT VOLTAGE (V) MAX856-10 1.6 INCLUDES ALL EXTERNAL COMPONENT LEAKAGES. CAPACITOR LEAKAGE DOMINATES AT TA = +85°C. CAPS ARE SPRAGUE 595D 1.2 0 1.5 250 TA = +85°C 0.2 MAX856-06 100 200 50 150 REFERENCE LOAD CURRENT (µA) QUIESCENT CURRENT vs. INPUT VOLTAGE 90 80 0.8 0.7 0.6 TA = +85°C 0.5 TA = +25°C 0.4 0.3 300 LOAD CURRENT (mA) LOAD CURRENT (mA) QUIESCENT CURRENT (mA) TA = -40°C MAX856-13 0 250 VOUT = 3.3V 200 VOUT = 5.0V 150 100 0.2 0 2.0 2.5 3.0 INPUT VOLTAGE (V) 3.5 4.0 VOUT = 3.3V 60 VOUT = 5.0V 50 40 30 10 0 0 1.5 70 20 50 TA = -40°C 0.1 4 TA = +25°C 0 0 0 MAX856-08 250 50 1 INCLUDES ALL EXTERNAL COMPONENT LEAKAGES. CAPACITOR LEAKAGE DOMINATES AT TA = +85°C. CAPS ARE SPRAGUE 595 D 300 150 1.6 1.4 QUIESCENT CURRENT (mA) 8 TA = +85°C 350 QUIESCENT CURRENT (µA) 9 VREF LOAD REGULATION (mV) 400 MAX856-05 10 MAX858/MAX859 NO LOAD BATTERY CURRENT vs. INPUT VOLTAGE MAX856-09 REFERENCE VOLTAGE vs. CURRENT SHUTDOWN CURRENT (µA) MAX856–MAX859 3.3V/5V or Adjustable-Output, Step-Up DC-DC Converters 1.0 1.5 2.0 2.5 3.0 INPUT VOLTAGE (V) 3.5 4.0 1.0 1.5 2.0 2.5 3.0 INPUT VOLTAGE (V) _______________________________________________________________________________________ 3.5 4.0 3.3V/5V or Adjustable-Output, Step-Up DC-DC Converters MAX856/MAX857 LOAD-TRANSIENT RESPONSE (5V MODE) MAX856/MAX857 LINE-TRANSIENT RESPONSE (5V MODE) VOUT 50mV/div VOUT 50mV/div 3V VIN 2V ILOAD 0mA to 100mA VIN = 2.5V 2ms/div VOUT 50mV/div 50µs/div MAX858/MAX859 LOAD-TRANSIENT RESPONSE MAX859 LINE-TRANSIENT RESPONSE VOUT 50mV/div ILOAD 3V 0 0mA to 25mA VIN 2V 1V/div 25 VIN = 2.5V 1ms/div MAX856 START-UP DELAY (5V MODE) VOUT 2V/div 2ms/div MAX858/MAX859 START-UP DELAY (5V MODE) VOUT 2V/div VSHDN 5V/div VSHDN 5V/div VIN = 2.5V, ILOAD = 100mA 5ms/div VIN = 2.5V, ILOAD = 25mA 5ms/div _______________________________________________________________________________________ 5 MAX856–MAX859 _____________________________Typical Operating Characteristics (continued) (Circuits of Figure 2, TA = +25°C, unless otherwise noted.) MAX856–MAX859 3.3V/5V or Adjustable-Output, Step-Up DC-DC Converters ______________________________________________________________Pin Description PIN NAME FUNCTION MAX856 MAX858 MAX857 MAX859 1 1 –———– SHDN 2 — –– 3/ 5 Selects the output voltage; connect to GND for 5V output, and to OUT for 3.3V output. — 2 FB Feedback Input for adjustable-output operation. Connect to an external resistor voltage divider between OUT and GND. 3 3 REF 1.25V Reference Voltage Output. Bypass with 0.22µF to GND (0.1µF if there is no external reference load). Maximum load capability is 250µA source, 20µA sink. 4 4 LBO Low-Battery Output. An open-drain N-channel MOSFET sinks current when the voltage at LBI drops below 1.25V. 5 5 LBI Low-Battery Input. When the voltage on LBI drops below 1.25V, LBO sinks current. If not used, connect to VIN. 6 6 OUT Connect OUT to the regulator output. OUT provides bootstrap power to the IC. 7 7 GND Power Ground. Must be low impedance; solder directly to ground plane. 8 8 LX Shutdown Input. When low, the entire circuit is off and VOUT = VIN - VD, where VD is the forward voltage drop of the external Schottky rectifier. N-Channel Power-MOSFET Drain _______________Detailed Description Operating Principle The MAX856–MAX859 combine a switch-mode regulator, N-channel power MOSFET, precision voltage reference, and power-fail detector in a single monolithic device. The MOSFET is a “sense-FET” type for best efficiency, and has a very low gate threshold voltage to ensure start-up with low battery voltages (0.8V typ). PFM Control Scheme A unique minimum-off-time, current-limited pulse-frequency modulation (PFM) control scheme is a key feature of the MAX856 series (Figure 1). This scheme combines the high output power and efficiency of a pulse-width modulation (PWM) device with the ultra-low quiescent current of a traditional PFM pulse-skipper. There is no oscillator; at heavy loads, switching is accomplished through a constant-peak-current limit in the switch, which allows the inductor current to vary between this peak limit and some lesser value. At light loads, switching frequency is governed by a pair of one-shots, which set a minimum off-time (1µs) and a maximum on-time (4µs). The switching frequency depends upon the load and the input voltage, and can range up to 500kHz. 6 The peak switch current of the internal MOSFET power switch is fixed at 500mA ±100mA (MAX856/MAX857) or 125mA ±25mA (MAX858/MAX859). The switch’s onresistance is typically 1Ω (MAX856/MAX857) or 4Ω (MAX858/MAX859), resulting in a switch voltage drop (VSW) of about 500mV under high output loads. The value of VSW will decrease with light current loads. Conventional PWM converters generate constant-frequency switching noise, whereas the unique architecture of the MAX856–MAX859 produces variable-frequency switching noise. However, unlike conventional pulse-skippers (where noise amplitude varies with input voltage), noise in the MAX856 series does not exceed the switch current limit times the filter-capacitor equivalent series resistance (ESR). Voltage Reference The precision voltage reference is suitable for driving external loads, such as an analog-to-digital converter. The voltage-reference output changes less than ±2% when sourcing up to 250µA and sinking up to 20µA. If the reference drives an external load, bypass it with 0.22µF to GND. If the reference is unloaded, bypass it with at least 0.1µF. _______________________________________________________________________________________ 3.3V/5V or Adjustable-Output, Step-Up DC-DC Converters MAX856–MAX859 MINIMUM OFF-TIME ONE-SHOT VIN TRIG Q ONE-SHOT SHDN LX VOUT F/F S N Q R 3/5* MAXIMUM ON-TIME ONE-SHOT GND Q TRIG ONE-SHOT CURRENT-LIMIT COMPARATOR OUT MAX856–MAX859 ** * FB** ** * ERROR COMPARATOR LBO REF N LBI COMPARATOR LBI REFERENCE *MAX856/MAX858 ONLY **MAX857/MAX859 ONLY Figure 1. Block Diagram _______________________________________________________________________________________ 7 MAX856–MAX859 3.3V/5V or Adjustable-Output, Step-Up DC-DC Converters Logic Inputs and Outputs The 3/5 input is internally diode clamped to GND and OUT, and should not be connected to signals outside this range. The SHDN input and LBO output (opendrain) are not clamped to V+ and can be pulled as high as 7V regardless of the voltage at OUT. Do not leave control inputs (3/5, LBI, or SHDN) floating. put will follow the battery voltage. This is acceptable in many systems; however, the input or output voltage must not be forced above 7V. The MAX857/MAX859’s output voltage is set by two resistors, R1 and R2 (Figure 2b), which form a voltage divider between the output and FB. Use the following equation to determine the output voltage: __________________Design Procedure R1 + R2 ) VOUT = VREF ( _________ R2 Output Voltage Selection For the MAX856/MAX858,you can select a 3.3V or– 5V output voltage under logic control, or by tying 3/ 5 to GND or OUT. Efficiency is typically better than 80% over a 2mA to 100mA (MAX856/MAX857) load range. The device is internally bootstrapped, with power derived from the output voltage (via OUT). When the output is in 5V mode, the higher internal supply voltage results in lower switch-transistor on-resistance, slightly greater output power, and higher efficiency. Bootstrapping allows the battery voltage to sag to 0.8V once the system is started. Therefore, the battery voltage ranges from (VOUT + VD) to 0.8V (where VD is the forward drop of the Schottky rectifier). If the battery voltage exceeds the programmed output voltage, the out- where VREF = 1.25V. To simplify resistor selection: VOUT - 1) R1 = R2 ( _______ VREF Since the input bias current at FB has a maximum value of 100nA, large values (10kΩ to 300kΩ) can be used for R1 and R2 with no significant accuracy loss. For 1% error, the current through R1 should be at least 100 times FB’s bias current. VIN C1* L1 5 LX LBI MAX856/MAX858 R4 OUT 1 3 3/5 SHDN LBO REF 8 D1 1N5817 VOUT C2* 6 2 47µH L1 R3 R1 5 1 *C1 = C2 = 68µF FOR MAX856 C1 = C2 = 22µF FOR MAX858 Figure 2a. Standard Application Circuit—Preset Output Voltage 3 C3 0.1µF FB SHDN LBO REF 8 D1 1N5817 VOUT C2* OUT 4 GND LX LBI MAX857/MAX859 R4 OUTPUT SELECT 7 8 C1* 47µH R3 C3 0.1µF VIN 6 R1 2 4 R2 GND 7 *C1 = C2 = 68µF FOR MAX857 C1 = C2 = 22µF FOR MAX859 Figure 2b. Standard Application Circuit—Adjustable Output Voltage _______________________________________________________________________________________ 3.3V/5V or Adjustable-Output, Step-Up DC-DC Converters Capacitor Selection A 68µF, 10V, 0.85Ω, surface-mount tantalum (SMT) output filter capacitor typically provides 50mV output ripple when stepping up from 2V to 5V at 100mA (MAX856/ MAX857). Smaller capacitors (down to 10µF with higher ESRs) are acceptable for light loads or in applications that can tolerate higher output ripple. Values in the 10µF to 47µF range are recommended for the MAX858/MAX859. The equivalent series resistance (ESR) of both bypass and filter capacitors affects efficiency and output ripple. The output voltage ripple is the product of the peak inductor current and the output capacitor’s ESR. Use low-ESR capacitors for best performance, or connect two or more filter capacitors in parallel. Low-ESR, SMT tantalum capacitors are currently available from Sprague (595D series) and AVX (TPS series). Sanyo OS-CON organic-semiconductor through-hole capacitors also exhibit very low ESR, and are especially useful for operation at cold temperatures. See Table 1 for a list of suggested capacitor suppliers. VLBI - 1) R3 = R4 ( ______ VREF where VLBI is the desired threshold of the low-battery detector and VREF is the internal 1.25V reference. Since the LBI current is less than 100nA, large resistor values (typically 10kΩ to 300kΩ) can be used for R3 and R4 to minimize loading of the input supply. When the voltage at LBI is below the internal threshold, LBO sinks current to GND. Connect a pull-up resistor of 10kΩ or more from LBO to OUT when driving CMOS circuits. When LBI is above the threshold, the LBO output is off. If the low-battery comparator is not used, connect LBI to VIN and leave LBO open. Inductor Selection An inductor value of 47µH performs well in most MAX856–MAX859 applications. However, the inductance value is not critical, and the MAX856–MAX859 will work with inductors in the 10µH to 100µH range. Smaller inductance values typically offer a smaller physical size for a given series resistance, allowing the smallest overall circuit dimensions. However, due to higher peak inductor currents, the output voltage ripple (I PEAK x output filter capacitor ESR) also tends to be higher. Circuits using larger inductance values exhibit higher output current capability and larger physical dimensions for a given series resistance. The inductor’s incremental saturation current rating should be greater than the peak switch-current limit, which is 500mA for the MAX856/MAX857, and 125mA for the MAX858/MAX859. However, it is generally acceptable to bias the inductor into saturation by as much as 20%, although this will slightly reduce efficiency. The inductor’s DC resistance significantly affects efficiency. See the Efficiency vs. Load Current for Various Inductors graph in the Typical Operating Characteristics. See Tables 1 and 2 for a list of suggested inductor suppliers. Rectifier Diode For optimum performance, a switching Schottky diode (such as the 1N5817) is recommended. Refer to Table 1 for a list of component suppliers. For low output power applications, a PN-junction switching diode (such as the 1N4148) will also work well, although its greater forward voltage drop will reduce efficiency. PC Layout and Grounding The MAX856 series’ high-frequency operation makes PC layout important for minimizing ground bounce and noise. Keep the IC’s GND pin and the ground leads of C1 and C2 (Figure 1) less than 0.2in (5mm) apart. Also keep all connections to the FB and LX pins as short as possible. To maximize output power and efficiency and minimize output ripple voltage, use a ground plane and solder the IC’s GND (pin 7) directly to the ground plane. _______________________________________________________________________________________ 9 MAX856–MAX859 Low-Battery Detection The MAX856 series contains an on-chip comparator for low-battery detection. If the voltage at LBI falls below the regulator’s internal reference voltage (1.25V), LBO (an open-drain output) sinks current to GND. The lowbattery monitor’s threshold is set by two resistors, R3 and R4 (Figure 2). Set the threshold voltage using the following equation: MAX856–MAX859 3.3V/5V or Adjustable-Output, Step-Up DC-DC Converters Table 1. Component Suppliers PRODUCTION METHOD INDUCTORS Surface Mount See Table 2 Miniature Through Hole Sumida RCH654-220 Low-Cost Through Hole CAPACITORS RECTIFIERS Matsuo 267 series Sprague 595D series AVX TPS series Motorola MBR 0530 Nihon EC15QS02L Sanyo OS-CON series low-ESR organic semiconductor Maxim MAXC001 150µF, low-ESR electrolytic Renco RL 1284-22 Nichicon PL series low-ESR electrolytic CoilCraft PCH-27-223 Motorola 1N5817 United Chemi-Con LXF series COMPANY PHONE FAX AVX USA: (207) 282-5111 (207) 283-1941 CoilCraft USA: (708) 639-6400 (708) 639-1469 Coiltronics USA: (407) 241-7876 (407) 241-9339 Matsuo USA: (714) 969-2491 (714) 960-6492 Motorola USA: (408) 749-0510 (800) 521-6274 Murata-Erie USA: (800) 831-9172 (404) 684-1541 Nichicon USA: (708) 843-7500 (708) 843-2798 Nihon USA: (805) 867-2555 Japan: 81-3-3494-7411 (805) 867-2556 81-3-3494-7414 Renco USA: (516) 586-5566 (516) 586-5562 Sanyo USA: (619) 661-6835 Japan: 81-7-2070-6306 USA: (708) 956-0666 Japan: 81-3-3607-5111 USA: (708) 803-6100 Japan: 03-3278-5111 (619) 661-1055 81-7-2070-1174 (708) 956-0702 81-3-3607-5144 (708) 803-6294 03-3278-5358 USA: (714) 255-9500 (714) 255-9400 Sumida TDK United Chemi-Con 10 ______________________________________________________________________________________ 3.3V/5V or Adjustable-Output, Step-Up DC-DC Converters MAX856–MAX859 Table 2. Surface-Mount Inductor Information INDUCTANCE (mH) RESISTANCE (W) RATED CURRENT (A) HEIGHT (mm) Sumida CDR105B-470 47 0.14 1.0 5.0 Sumida CDR74B-470 47 0.27 0.8 4.5 Sumida CD43-470 47 0.85 0.540 3.2 Sumida CD43-220 22 0.38 0.760 3.2 Murata-Erie LQH4N220 22 0.94 0.320 2.6 Murata-Erie LQH4N470 47 1.5 0.220 2.6 Murata-Erie LQH1N220 22 3.1 0.85 1.8 TDK NLC322522T-220K 22 1.15 0.210 2.2 TDK NLC322522T-470K 47 2.25 0.150 2.2 Coiltronics CTX20-1 20 0.175 1.15 4.2 Coilcraft DT1608-223 22 0.16 0.500 3.2 MANUFACTURER PART __Ordering Information (continued) PART TEMP. RANGE MAX858CSA 0°C to +70°C MAX858CUA MAX858C/D MAX858ESA MAX858MJA MAX859CSA MAX859CUA MAX859C/D MAX859ESA MAX859MJA 0°C to +70°C 0°C to +70°C -40°C to +85°C -55°C to +125°C 0°C to +70°C 0°C to +70°C 0°C to +70°C -40°C to +85°C -55°C to +125°C * Dice are tested at TA = +25°C only. † Contact factory for availability. ___________________Chip Topography PIN-PACKAGE 8 SO 8 µMAX Dice* 8 SO 8 CERDIP† 8 SO 8 µMAX Dice* 8 SO 8 CERDIP† LX SHDN 3/5 OR FB* GND 0.084" (2.1336mm) REF OUT LBI LBO 0.058" (1.4732mm) *3/5 FOR MAX856/MAX858; FB FOR MAX857/MAX859. TRANSISTOR COUNT: 357; SUBSTRATE CONNECTED TO OUT. ______________________________________________________________________________________ 11 MAX856–MAX859 3.3V/5V or Adjustable-Output, Step-Up DC-DC Converters ________________________________________________________Package Information DIM C α A 0.101mm 0.004 in e B A1 L E A A1 B C D E e H L α INCHES MAX MIN 0.044 0.036 0.008 0.004 0.014 0.010 0.007 0.005 0.120 0.116 0.120 0.116 0.0256 0.198 0.188 0.026 0.016 6° 0° MILLIMETERS MIN MAX 0.91 1.11 0.10 0.20 0.25 0.36 0.13 0.18 2.95 3.05 2.95 3.05 0.65 4.78 5.03 0.41 0.66 0° 6° INCHES MAX MIN 0.069 0.053 0.010 0.004 0.019 0.014 0.010 0.007 0.157 0.150 0.050 0.244 0.228 0.050 0.016 MILLIMETERS MIN MAX 1.35 1.75 0.10 0.25 0.35 0.49 0.19 0.25 3.80 4.00 1.27 5.80 6.20 0.40 1.27 H 8-PIN µMAX MICROMAX SMALL OUTLINE PACKAGE D DIM D 0°-8° A 0.101mm 0.004in. e B A1 E 12 C H L Narrow SO SMALL-OUTLINE PACKAGE (0.150 in.) A A1 B C E e H L DIM PINS D D D 8 14 16 INCHES MILLIMETERS MIN MAX MIN MAX 0.189 0.197 4.80 5.00 0.337 0.344 8.55 8.75 0.386 0.394 9.80 10.00 ______________________________________________________________________________________ 21-0041A