PART MAX682ESA MAX684EUA TOP VIEW SKIP. OUTPUT 5V/250mA CXN SKIP

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1 19-177; Rev 1; 8/98 3.3V-Input to Regulated 5V-Output General Description The charge-pump regulators generate 5V from a 2.7V to 5.5V input. They are specifically designed to serve as high-efficiency auxiliary supplies in applications that demand a compact design. The,, and deliver 25mA, ma, and 5mA output current, respectively. These complete 5V regulators require only one resistor and three external capacitors no inductors are needed. High switching frequencies (externally adjustable up to 2MHz) and a unique regulation scheme allow the use of capacitors as small as 1µF per ma of output current. The / are offered in a spacesaving 8-pin µmax package that is only 1.1mm high, while the is available in an 8-pin SO. Applications Flash Memory Supplies Battery-Powered Applications Miniature Equipment PCMCIA Cards 3.3V to 5V Local Conversion Applications Backup-Battery Boost Converters 3V to 5V GSM SIMM Cards Features Ultra-Small: 1µF Capacitors per ma of Output Current No Inductors Required 1.1mm Height in µmax Package (/) Up to 25mA Output Current () Regulated ±4% Output Voltage 5kHz to 2MHz Adjustable Switching Frequency 2.7V to 5.5V Input Voltage µa Quiescent Current in Pulse-Skipping Mode.1µA Shutdown Current PART ESA EUA EUA Ordering Information TEMP. RANGE -4 C to +85 C -4 C to +85 C -4 C to +85 C P-PACKAGE 8 SO 8 µmax 8 µmax Typical Operating Circuit Pin Configurations TOP VIEW PUT 2.7V TO 5.5V R EXT PUT 5V/25mA GND 4 5 GND 4 5 GND SO µmax Maxim Integrated Products 1 For free samples & the latest literature: or phone For small orders, phone ext

2 ABSOLUTE MAXIMUM RATGS,,, to GND...-.3V to +6V to GND...±.3V to GND...-.3V to (V +.3V) to GND...-.3V to (V +.3V) Continuous Output Current...3mA...15mA...75mA Output Short-Circuit Duration...5sec 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 Continuous Power Dissipation (T A = +7 C) 8-Pin SO (derate 5.9mW/ C above +7 C)...471mW 8-Pin µmax (derate 4.1mW/ C above +7 C)...33mW Operating Temperature Range MAX68_E_A...-4 C to +85 C Junction Temperature C Storage Temperature Range C to +16 C Lead Temperature (soldering, sec)...+3 C (V = 3V, V = V, C = 1µF, C X =.47µF, C = 2µF, I = 22µA; I MAX = 25mA for, I MAX = ma for, I MAX = 5mA for ; T A = T M to T MAX, unless otherwise noted. Typical values are at T A = +25 C.) (Note 1) PARAMETER Input Voltage Range Input Undervoltage Lockout Threshold Input Undervoltage Lockout Hysteresis SYMBOL V CONDITIONS Regulation with V > 3.6V requires = high M TYP MAX UNITS V V mv Output Voltage Maximum Output Current No-Load Input Current Load Regulation Logic Low Input On Bias Voltage Input Current Range Switching Frequency (Note 2) Shutdown Supply Current Shutdown Exit Time V I MAX I Q V LDR V L, V ON, I I Q, t START < I 3.V LOAD I 3.6V MAX ; for, 3.V 3.6V for =, 3.V 5.5V for = =, V = 3.6V = high, I LOAD I MAX T A = +25 C (Note 2) I = 22µA I =4.4µA C < T A < +85 C -4 C < T A < +85 C C < T A < +85 C =, V = 5.5V, V =.1 5 µa R L = 5V/I MAX 5 µs 25 5 = V = 3.6V -4 C < T A < +85 C V ma ma % V mv µa khz 2

3 ELECTRICAL CHARACTERISTICS (continued) (V = 3V, V = V, C = 1µF, C X =.47µF, C = 2µF, I = 22µA; I MAX = 25mA for, I MAX = ma for, I MAX = 5mA for ; T A = T M to T MAX, unless otherwise noted. Typical values are at T A = +25 C.) (Note 1) PARAMETER Input Voltage Low Input Voltage High Input Leakage Current SYMBOL V L, V H, I V = 5.5V CONDITIONS V = 5.5V, V = V or 5.5V Note 1: Specifications to -4 C are guaranteed by design and not production tested. Note 2: Current into determines oscillator frequency: R EXT (kω) = 45 (V -.69V) / f OSC (khz) M TYP MAX UNITS Typical Operating Characteristics (Circuit of Figure 5, V = 3.3V, component values from Tables 2 and 3, T A = +25 C, unless otherwise noted.) SUPPLY CURRENT (ma) NO-LOAD SUPPLY CURRENT vs. SUPPLY VOLTAGE = HIGH I = 22µA TOC1 PUT VOLTAGE (V) PUT VOLTAGE vs. LOAD CURRENT ( = LOW) TOC3 PUT VOLTAGE (V) V µa PUT VOLTAGE vs. LOAD CURRENT ( = HIGH) = HIGH I = 22µA TOC SUPPLY VOLTAGE (V) PUT VOLTAGE (V) = LOW PUT VOLTAGE vs. SUPPLY VOLTAGE = HIGH TOC6 OSCILLATOR FREQUENCY (Hz) M 1M k OSCILLATOR FREQUENCY vs. SHUTDOWN P PUT CURRENT TOC8 NO-LOAD SUPPLY CURRENT (ma) 1 NO-LOAD SUPPLY CURRENT vs. SHUTDOWN P PUT CURRENT = HIGH TOC SUPPLY VOLTAGE (V) k.1 1 PUT CURRENT (µa) PUT CURRENT (µa) 3

4 Typical Operating Characteristics (continued) (Circuit of Figure 5, V = 3.3V, component values from Tables 2 and 3, T A = +25 C, unless otherwise noted.) EFFICIENCY (%) EFFICIENCY (%) EFFICIENCY vs. LOAD CURRENT ( = LOW) V = 3.V V = 3.3V.1 1 EFFICIENCY vs. LOAD CURRENT ( = HIGH) V = 3.V V = 3.3V V = 5.V V = 3.6V I = 22µA 1 TOC TOC13 EFFICIENCY (%) EFFICIENCY (%) EFFICIENCY vs. LOAD CURRENT ( = LOW) V = 3.V V = 3.3V.1 1 EFFICIENCY vs. LOAD CURRENT ( = HIGH) V = 3.V V = 3.3V V = 5.V V = 3.6V I = 22µA 1 TOC11 TOC14 EFFICIENCY (%) EFFICIENCY (%) EFFICIENCY vs. LOAD CURRENT ( = LOW) EFFICIENCY vs. LOAD CURRENT ( = HIGH) V = 3.V V = 3.V V = 3.3V.1 1 V = 3.3V V = 5.V V = 3.6V I = 22µA 1 TOC12 TOC15 PUT WAVEFORM ( = HIGH) TOC16 PUT WAVEFORM ( = LOW) TOC17 5mV/div 5mV/div 2ns/div = HIGH, I = 22µA, I LOAD = 25mA, 2ns/div = LOW, I LOAD = 25mA, 4

5 Typical Operating Characteristics (continued) (Circuit of Figure 5, V = 3.3V, component values from Tables 2 and 3, T A = +25 C, unless otherwise noted.) SHUTDOWN TIMG µs/div TOC18 A: PUT VOLTAGE: = HIGH, R L = 5V / I MAX, 2V/div B: VOLTAGE: 1V/div A B LE-TRANSIENT RESPONSE 2ms/div TOC2 A: PUT VOLTAGE: V = 3.1V TO 3.6V, 5mV/div B: PUT VOLTAGE: = HIGH, I = 22µA, I LOAD = 25mA, 5mV/div, A B LOAD-TRANSIENT RESPONSE 2ms/div TOC19 A: LOAD CURRENT: I LOAD = 5mA TO 25mA, 5mA/div B: PUT VOLTAGE: = HIGH, I = 22µA, mv/div, Pin Description A B P NAME FUNCTION When = low, the regulator operates in low-quiescent-current skip mode. When = high, the regulator operates in constant-frequency mode, minimizing output ripple and noise. must be tied high for input voltages above 3.6V. Shutdown Input. Drive through an external resistor. When = low, the device turns off. When current is sourced into through R EXT, the device activates, and the pin input current sets the oscillator s switching frequency. R EXT (kω) = 45 (V -.69V) / f OSC (khz). Input Supply Pin. Can range from 2.7V to 5.5V for = high, and 2.7V to 3.6V for = low. Bypass to with a suitable value capacitor (see Capacitor Selection section). 4 GND Ground Pin. Connect to through a short trace. 5 Power Ground Pin 6 Negative Terminal of the Charge-Pump Transfer Capacitor 7 Positive Terminal of the Charge-Pump Transfer Capacitor 8 Fixed 5V Power Output. Bypass to with output filter capacitor. 5

6 Detailed Description The charge pumps provide a regulated 5V output from a 2.7V to 5.5V input. They deliver a maximum of 25mA, ma, or 5mA load current, respectively. Designed specifically for compact applications, a complete regulator circuit requires only three small external capacitors and one resistor. An externally adjustable switching frequency and innovative control scheme allow the circuit to be optimized for efficiency, size, or output noise. The devices also contain a shutdown feature. The consist of an error amplifier, a 1.23V bandgap reference, an internal resistive feedback network, an oscillator, high-current MOS- FET switches, and shutdown and control logic (Figure 1). Figure 2 shows an idealized unregulated chargepump voltage doubler. The oscillator runs at a 5% duty cycle. During one half of the period, the transfer capacitor (C X ) charges to the input voltage. During the other half, the doubler stacks the voltage across C X and the input voltage, and transfers the sum of the two voltages to the output filter capacitor (C ). Rather than simply doubling the input voltage, the provide a regulated fixed output voltage (5V) using either skip mode or constantfrequency mode. Skip mode and constant-frequency mode are externally selected via the input pin. S2 C S1 X C OSC Figure 2. Unregulated Voltage Doubler S2 C X S1 C EN OSCILLATOR C Figure 3. Skip-Mode Regulation CONTROL LOGIC EN OSC Figure 1. Functional Block Diagram 1.23V SWITCHES Skip Mode In skip mode ( = low), the error amplifier disables switching when it detects an output higher than 5V. The device then skips switching cycles until the output voltage drops. Then the error amplifier reactivates the oscillator. Figure 3 illustrates the regulation scheme. This regulation method minimizes operating current because the device does not switch continuously. is a logic input and should not remain floating. Constant-Frequency Mode When is high, the charge pump runs continuously at the selected frequency. Figure 4 shows a block diagram of the device in constant-frequency mode. The error amplifier controls the charge on C X by driving the gate of the N-channel FET. When the output voltage falls, the gate drive increases, resulting in a larger voltage across C X. This regulation scheme minimizes output ripple. Since the device switches continuously, the 6

7 C S1 N-CHANNEL C X S2 OSC Figure 4. Constant-Frequency-Mode Regulation Table 1. Tradeoffs Between Operating Modes FEATURE Best Light-Load Efficiency Smallest External Component Size Output Ripple Amplitude and Frequency MODE ( = LOW) Relatively large amplitude, variable frequency output noise contains well-defined frequency components, and the circuit requires much smaller external capacitors for a given output ripple. However, constantfrequency mode, due to higher operating current, is less efficient at light loads than skip mode. Note: For input voltages above 3.6V, the devices must operate in constant-frequency mode. Table 1 summarizes the tradeoffs between the two operating modes. Frequency Selection and Shutdown The pin on the performs a dual function: it shuts down the device and determines the oscillator frequency. The input looks like a diode to ground and should be driven through a resistor. Driving low places the device in shutdown mode. This disables all switches, the oscillator, and control logic. The device typically draws.1µa (5µA C CONSTANT- FREQUENCY MODE ( = HIGH) Relatively small amplitude, constant frequency Load Regulation Very Good Good max) of supply current in this mode and the output presents a 5kΩ impedance to ground. The device exits shutdown once is forward biased (minimum of 1µA of current). The typical no-load shutdown exit time is 5µs. When is pulled high through an external resistor to V, the bias current into determines the charge-pump frequency. To select the frequency, calculate the external resistor value, R EXT, using the following formula: R EXT = 45 (V -.69V) / f OSC where R EXT is in kω and f OSC is in khz. Program the frequency in the 5kHz to 2MHz range. This frequency range corresponds to input currents between 1µA and 5µA. Proper operation of the oscillator is not guaranteed beyond these limits. Currents lower than 1µA may shut down the device. The forward-biased diode voltage from the input to GND has a temperature coefficient of -2mV/ C. Undervoltage Lockout The have an undervoltagelockout feature that deactivates the devices when the input voltage falls below 2.25V. Regulation at low input voltages cannot be maintained. This safety feature ensures that the device shuts down before the output voltage falls out of regulation by a considerable amount (typically % with no load). Once deactivated, hysteresis holds the device in shutdown until the input voltage rises mv above the lockout threshold. Applications Information Capacitor Selection The require only three external capacitors (Figure 5). Their values are closely linked to the output current capacity, oscillator frequency, output noise content, and mode of operation. Generally, the transfer capacitor (C X ) will be the smallest, and the input capacitor (C ) is twice as large as C X. Higher switching frequencies allow the use of smaller C X and C. The output capacitor (C ) can be anywhere from 5-times to 5-times larger than C X, depending on the mode of operation and ripple tolerance. In continuous switching mode, smaller output ripple allows smaller C. In skip mode, a larger C is required to maintain low output ripple. Tables 2 and 3 show capacitor values recommended for lowest supply-current operation (skip mode) and smallest size operation (constant-frequency mode), respectively. 7

8 Table 2. Recommended Capacitor Values for Quiescent Current (Skip Mode) PART PUT (ma) C (µf) C X (µf) V RIPPLE (mv) Table 3. Recommended Capacitor Values for Smallest Size (Constant-Frequency Mode, I = 22µA, 1MHz) PART PUT (ma) C (µf) C X (µf) C (µf) TANTALUM CERAMIC CERAMIC C (µf) V RIPPLE (mv) 3.3V 1µF ON OFF k V ON C R EXT GND 4 5 Figure 5. Standard Operating Circuit k 1µF C X C 5V/5mA 4.7µF µF.47µF GND GND Table 4. Recommended Capacitor Manufacturers VALUE 47µF to µf 47µF to µf.1µf to 2.2µF DESCRIPTION 595D-series tantalum surface mount TPS-series surface mount Ceramic surface mount MANUFACTURER PHONE NUMBER Sprague (63) AVX (3) TDK (847) In addition, the following two equations approximate output ripple for each mode. In skip mode, output ripple is dominated by ESR, and is approximately: V RIPPLE() (2V - V )ESR C / R TX Figure 6. Paralleling Two s where ESR C is the ESR of the output filter capacitance, and RTX is the open-loop output transfer resistance of the IC. RTX is typically.8ω for the, 1.6Ω for the, and 3Ω for the. In constant-frequency mode, output ripple is dominated by C and is approximately: V RIPPLE(const-freq) I / (2 x f OSC x C ) All capacitors must maintain a low (<mω) equivalent series resistance (ESR). Table 4 lists the manufacturers of recommended capacitors. Surface-mount tantalum capacitors will work well for most applications. Ceramic capacitors will provide the lowest ripple due to their typically lower ESR. If the source impedance or inductance of the input supply is large, additional input bypassing (2.2µF to 22µF) may be needed. This additional capacitance need not be a low-esr type. 8

9 Power Dissipation The power dissipated in the depends on output current and is accurately described by: P DISS = I (2V - V ) P DISS must be less than that allowed by the package rating. See the Absolute Maximum Ratings for 8-pin µmax (/) and SO () powerdissipation limits and deratings. Layout Considerations All capacitors should be soldered in close proximity to the IC. Connect ground and power ground through a short, low-impedance trace. If a high-value resistor is driving the shutdown input and is picking up noise (i.e., frequency jitter at and ), bypass to GND with a small capacitor (.1µF). Paralleling Devices The can be paralleled to yield higher load currents. The circuit of Figure 6 can deliver 5mA at 5V. It uses two s in parallel. The devices can share the output capacitors, but each one requires its own transfer capacitor (C X ) and input capacitor. For best performance, the paralleled devices should operate in the same mode (skip or constant frequency). TRANSISTOR COUNT: 659 SUBSTRATE CONNECTED TO GND Chip Information Package Information 8LUMAXD.EPS 9

10 Package Information SOICN.EPS

11 NOTES 11

12 NOTES 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. 12 Maxim Integrated Products, 12 San Gabriel Drive, Sunnyvale, CA Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.