View MAX1759_50622.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

19-1600; Rev 0; 1/00
Buck/Boost Regulating Charge Pump in MAX
General Description
The MAX1759 is a buck/boost regulating charge pump that generates a regulated output voltage from a single lithium-ion (Li+) cell, or two or three NiMH or alkaline cells for small hand-held portable equipment. The MAX1759 operates over a wide +1.6V to +5.5V input voltage range and generates a fixed 3.3V or adjustable (2.5V to 5.5V) output (Dual ModeTM). Maxim's unique charge-pump architecture allows the input voltage to be higher or lower than the regulated output voltage. Despite its high 1.5MHz operating frequency, the MAX1759 maintains low 50A quiescent supply current. Designed to be an extremely compact buck/boost converter, this device requires only three small ceramic capacitors to build a complete DC-DC converter capable of generating a guaranteed 100mA (min) output current from a +2.5V input. For added flexibility, the MAX1759 also includes an open-drain power-OK (POK) output that signals when the output voltage is in regulation. The MAX1759 is available in a space-saving 10-pin MAX package that is 1.09mm high and half the size of an 8-pin SO.
Features
o Regulated Output Voltage (Fixed 3.3V or Adjustable 2.5V to 5.5V) o 100mA Guaranteed Output Current o +1.6V to +5.5V Input Voltage Range o Low 50A Quiescent Supply Current o 1A Shutdown Mode o Load Disconnected from Input in Shutdown o High 1.5MHz Operating Frequency o Uses Small Ceramic Capacitors o Short-Circuit Protection and Thermal Shutdown o Small 10-Pin MAX Package
MAX1759
Ordering Information Applications
Li+ Battery-Powered Applications Miniature Equipment Backup Battery Boost Converters Translators
PART MAX1759EUB TEMP. RANGE -40C to +85C PIN-PACKAGE 10 MAX
Typical Operating Circuit
CX IN +1.6V TO +5.5V CIN OUT 3.3V AT 100mA COUT
Pin Configuration
TOP VIEW
CXN IN
CXP OUT
POK 1 SHDN IN IN 2 3 4 5
10 FB 9 OUT CXP CXN PGND
MAX1759
MAX1759
ON OFF SHDN FB GND PGND POK POWER OK
8 7 6
GND
MAX
Dual Mode is a trademark of Maxim Integrated Products. ________________________________________________________________ Maxim Integrated Products 1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. For small orders, phone 1-800-835-8769.
Buck/Boost Regulating Charge Pump in MAX MAX1759
ABSOLUTE MAXIMUM RATINGS
IN, OUT, FB, POK, SHDN to GND............................-0.3V to +6V PGND to GND.....................................................................0.3V CXN to GND ................................................-0.3V to (VIN + 0.3V) CXP to GND..............................................-0.3V to (VOUT + 0.3V) OUT Short to GND .........................................................Indefinite Continuous Power Dissipation (TA = +70C) 10-Pin MAX (derate 5.6mW/C above +70C) .........444mW 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
(Circuit of Figure 1, VIN = V SHDN = 2V, FB = PGND = GND, CIN = 10F, CX = 0.33F, COUT = 10F, TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Input Voltage Range Input Undervoltage Lockout Voltage Output Voltage Adjustment Range Output Voltage Maximum Output Current Transient Load Current Quiescent Supply Current Shutdown Supply Current Leakage Current into OUT in Shutdown SHDN Logic Input Voltage SHDN Input Leakage Current FB Regulation Voltage FB Input Current FB Dual-Mode Threshold POK Trip Voltage POK Output Low Voltage POK Leakage Current Switching Frequency Output Short-Circuit Current Thermal Shutdown Temperature Thermal Shutdown Hysteresis Efficiency VIN = 3.6V, ILOAD = 10mA fOSC VOL VIL VIH I SHDN VFB IQ IQ,SHDN VOUT VIN VUVLO 1.6V VIN 5.5V 2V VIN 5.5V, 1mA ILOAD 50mA 2.5V VIN 5.5V, 1mA ILOAD 100mA ILOAD 100mA (RMS) VIN = V SHDN = 4V, VFB = 0, stepping down VIN = V SHDN = 2V, VFB = 0, stepping up 1.6V VIN 5.5V, V SHDN = 0 VIN = 2V, VOUT = 3.3V, V SHDN = 0 1.6V VIN 5.5V 1.6V VIN 5.5V V SHDN = 5.5V VIN = 1.65V, VOUT = 3.3V VFB = 1.27V Internal feedback External feedback Falling edge at FB ISINK = 0.5mA, VIN = 2V VPOK = 5.5V, VFB = 1.27V 1.6V VIN 5.5V, VFB = 1V VOUT = 0, 2.5V VIN 5.5V, foldback current limit Rising temperature 1.2 200 1.0 0.7 * VIN -1 1.205 1.235 25 100 100 1.1 5 0.01 1.5 110 160 20 90 1.2 100 0.2 1.8 1 1.265 200 50 1.6 0.6 2.5 3.17 3.17 100 200 50 85 1 1 90 180 5 5 0.25 * VIN 3.3 3.3 1.0 5.5 1.4 5.5 3.43 3.43 mA mA A A A V A V nA mV mV V mV A MHz mA C C % V V V V
ILOAD,MAX 2.5V VIN 5.5V
2
_______________________________________________________________________________________
Buck/Boost Regulating Charge Pump in MAX
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, VIN = V SHDN = 2V, FB = PGND = GND, CIN = 10F, CX = 0.33F, COUT = 10F, TA = -40C to +85C, unless otherwise noted.) (Note 1) PARAMETER Input Voltage Range Input Undervoltage Lockout Voltage Output Voltage Output Voltage Adjustment Range Maximum Output Current Quiescent Supply Current Shutdown Supply Current Leakage Current into OUT in Shutdown SHDN Input Logic Voltage SHDN Input Leakage Current FB Regulation Voltage FB Input Bias Current FB Dual Mode Threshold POK Trip Voltage POK Output Low Voltage POK Leakage Current Switching Frequency fOSC VOL VIL VIH I SHDN VFB SYMBOL VIN VUVLO VOUT 2V VIN 5.5V, 0 ILOAD 50mA 2.5V VIN 5.5V, 0 ILOAD 100mA 1.6V VIN 5.5V ILOAD,MAX 2.5V VIN 5.5V IQ IQ,SHDN VIN = V SHDN = 4V, VFB = 0 VIN = V SHDN = 2.5V, VFB = 0 1.6V VIN 5.5V, V SHDN = 0 VIN = 2V, VOUT = 3.3V, V SHDN = 0 1.6V VIN 5.5V 1.6V VIN 5.5V V SHDN = 5.5V VIN = 1.65V, VOUT = 3.3V VFB = 1.27V Internal feedback External feedback Falling edge at FB ISINK = 0.5mA, VIN = 2V VPOK = 5.5V 1.6V VIN 5.5V, VFB = 1V 1.1 200 1.0 1.2 100 0.2 1.9 0.7 * VIN -1 1.205 1 1.265 200 40 CONDITIONS MIN 1.6 0.6 3.15 3.15 2.5 100 90 180 6 5 0.2 * VIN MAX 5.5 1.4 3.45 3.45 5.5 UNITS V V V V V mA A A A V V A V nA mV mV V mV A MHz
MAX1759
Note 1: Specifications to -40C are guaranteed by design and are not production tested.
_______________________________________________________________________________________
3
Buck/Boost Regulating Charge Pump in MAX MAX1759
Typical Operating Characteristics
(Circuit of Figure 1, CIN = 10F, CX = 0.33F, COUT = 10F, VOUT = 3.3V, VIN = 2.5V, TA = +25C, unless otherwise noted.)
OUTPUT VOLTAGE RIPPLE vs. INPUT VOLTAGE
MAX1759 toc01
OUTPUT VOLTAGE vs. LOAD CURRENT
MAX1759 toc02
EFFICIENCY vs. INPUT VOLTAGE
90 80 EFFICIENCY (%) 70 60 50 40 30 IOUT = 100mA IOUT = 50mA IOUT = 10mA
MAX1759 toc03
100 OUTPUT VOLTAGE RIPPLE (mV) IOUT = 100mA
3.40
100
80
60
IOUT = 50mA
OUTPUT VOLTAGE (V)
3.35
3.30
40
3.25 20 IOUT = 10mA 0 1.5 2.5 3.5 INPUT VOLTAGE (V) 4.5 5.5 3.20 0.001
20 10 0 0.01 0.1 1 10 100 1000 1.5 2.5 3.5 INPUT VOLTAGE (V) 4.5 5.5 LOAD CURRENT (mA)
QUIESCENT CURRENT vs. INPUT VOLTAGE
MAX1759 toc04
MAX1759 toc05
RLOAD = 33 3
RLOAD = 33 VIN = 4.2V 1
QUIESCENT CURRENT (A)
OUTPUT VOLTAGE (V)
1000
100
2
2
10 1 0.5 1.5 2.5 3.5 INPUT VOLTAGE (V) NO LOAD 4.5 5.5
1 3 0 0.5 1.5 2.5 3.5 4.5 5.5 5s/div CH1: VOUT, 20mV/div, AC-COUPLED CH2: VCXP, 5V/div CH3: VIN, 50mV/div, AC-COUPLED INPUT VOLTAGE (V)
TYPICAL SWITCHING WAVEFORMS (VOUT > VIN)
MAX1759 toc07
LOAD-TRANSIENT RESPONSE (VOUT < VIN)
MAX1759 toc08
LOAD-TRANSIENT RESPONSE (VOUT > VIN)
MAX1759 toc09
RLOAD = 33 VIN = 2.5V 1
1
1
2
2 3 LOAD STEP: 10mA TO 100mA VIN = 4.2V 5s/div CH1: VOUT, 20mV/div, AC-COUPLED CH2: VCXP, 5V/div CH3: VIN, 50mV/div, AC-COUPLED 100s/div CH1: VOUT, 20mV/div, AC-COUPLED CH2: IOUT, 100mA/div
2 LOAD STEP: 10mA TO 100mA VIN = 2.5V 100s/div CH1: VOUT, 20mV/div, AC-COUPLED CH2: IOUT, 100mA/div
4
_______________________________________________________________________________________
MAX1759 toc06
10,000
STARTUP INPUT VOLTAGE (VOUT < VIN)
4
TYPICAL SWITCHING WAVEFORMS (VOUT < VIN)
Buck/Boost Regulating Charge Pump in MAX
Typical Operating Characteristics (continued)
(Circuit of Figure 1, CIN = 10F, CX = 0.33F, COUT = 10F, VOUT = 3.3V, VIN = 2.5V, TA = +25C, unless otherwise noted.)
MAX1759
LINE-TRANSIENT RESPONSE
MAX1759 toc10
TURN-ON/OFF RESPONSE (VIN = 4.2V)
MAX1759 toc11
TURN-ON/OFF RESPONSE (VIN = 2.5V)
RLOAD = 33 VIN = 2.5V
MAX1759 toc12
RLOAD = 33
RLOAD = 33 VIN = 4.2V
1
1 2 3 -2.5V 100s/div CH1: VOUT, 20mV/div, AC-COUPLED CH2: VIN, 1V/div, AC-COUPLED CH1: VOUT,1V/div CH2: IIN, 200mA/div CH3: VPOK, 5V/div CH4: VSHDN, 5V/div 4 500s/div
1 2 3 4 500s/div CH1: VOUT,1V/div CH2: IIN, 200mA/div CH3: VPOK, 5V/div CH4: VSHDN, 5V/div
-4.2V 2
Pin Description
PIN 1 NAME POK FUNCTION Open-Drain Power-OK Output. POK is high impedance when output voltage is in regulation. POK sinks current when VFB falls below 1.1V. Connect a 10k to 1M pull-up resistor from POK to VOUT for a logic signal. Ground POK or leave unconnected if not used. POK is high impedance in shutdown. Shutdown Input. Drive high for normal operation; drive low for shutdown mode. OUT is high impedance in shutdown. Input Supply. Connect both pins together and bypass to GND with a ceramic capacitor (see Capacitor Selection section). Ground. Connect GND to PGND with a short trace. Power Ground. Charge-pump current flows through this pin. Negative Terminal of the Charge-Pump Transfer Capacitor Positive Terminal of the Charge-Pump Transfer Capacitor Power Output. Bypass to GND with an output filter capacitor. Dual-Mode Feedback. Connect FB to GND for 3.3V output. Connect to an external resistor divider to adjust the output voltage from 2.5V to 5.5V.
2
SHDN
3, 4 5 6 7 8 9 10
IN GND PGND CXN CXP OUT FB
_______________________________________________________________________________________
5
Buck/Boost Regulating Charge Pump in MAX MAX1759
Detailed Description
The MAX1759's unique charge-pump architecture allows the input voltage to be higher or lower than the regulated output voltage. Internal circuitry senses VIN and V OUT and determines whether V IN must be stepped up or stepped down to produce the regulated output. When VIN is lower than VOUT, the charge pump operates as a regulated step-up voltage doubler. When VIN is higher than VOUT, the charge pump operates as a step-down gated switch. In voltage step-down mode (i.e., the input voltage is greater than the output voltage) with a light load, the controller connects CXN to PGND, and shuttles charge to the output by alternately connecting CXP from IN to OUT (see Figures 1 and 2). Although VIN is greater than VOUT, this scheme may not allow the MAX1759 to regulate the output under heavy loads. In this case, the MAX1759 will automatically switch to step-up mode. In step-up mode, the output is kept in regulation by modulating the charge delivered by the transfer capacitor (CX) to the load (see Figure 2). When lightly loaded, the charge pump switches only as necessary to supply the load, resulting in low quiescent current. Output voltage ripple does not increase with light loads.
IN +1.6V TO +5.5V 10F CXN IN 0.33F OUT 3.3V AT 100mA 10F
CXP OUT
MAX1759
ON OFF SHDN FB GND PGND POK
100k
POWER OK
Figure 1. Typical Application Circuit
Thermal Shutdown
The MAX1759 features thermal shutdown with temperature hysteresis. When the die temperature exceeds 160C, the device shuts down. When the die cools by 20C, the MAX1759 turns on again. If high die temperature is caused by output overload and the load is not removed, the device will turn off and on, resulting in a pulsed output.
Shutdown Mode
Driving SHDN low places the MAX1759 in shutdown mode. This disables the charge-pump switches, oscillator, and control logic, reducing quiescent current to 1A. The output is high impedance in shutdown and is disconnected from the input. The POK output is high impedance in shutdown.
Design Procedure
Setting the Output Voltage
The MAX1759 dual-mode feedback controller selects between the internally set 3.3V regulated output or an external resistive divider that allows adjustment of the output voltage from 2.5V to 5.5V. Connect FB to GND for a regulated 3.3V output. For an adjustable output, connect a resistive divider between OUT and GND. To ensure feedback-loop stability and to minimize error due to FB pin bias currents, the resistive divider current should be approximately 15A. In the following equation, choose R2 in the 50k to 100k range, and calculate R1 from the following formula (Figure 3): R1 = R2 [(VOUT / VFB) - 1] and VOUT = VFB (R1 + R2) / R2 where VOUT is the desired output voltage from 2.5V to 5.5V, and VFB is the internal regulation voltage, nominally 1.235V. The circuit of Figure 3 generates a regulated 2.5V, using external standard 1% resistor values. Surface-mount resistors should be placed close to the MAX1759, less than 5mm away from FB (see the PC Board Layout section).
Undervoltage Lockout
The MAX1759 undervoltage lockout feature deactivates the device when the input voltage falls below 1V.
Power-OK Output
POK is an open-drain output that sinks current when the regulator feedback voltage falls below 1.1V. The feedback voltage can be either the internal resistordivider feedback voltage when in fixed output mode (FB tied to GND) or an external feedback voltage from an external resistive divider in adjustable output mode. A 10k to 1M pull-up resistor from POK to OUT may be used to provide a logic output. Connect POK to GND or leave unconnected if not used.
Soft-Start and Short-Circuit Protection
The MAX1759 features foldback short-circuit protection. This circuitry provides soft-start by limiting inrush current during startup and limits the output current to 110mA (typ) if the output is short-circuited to ground.
6
_______________________________________________________________________________________
Buck/Boost Regulating Charge Pump in MAX MAX1759
CXN 7 IN 3, 4
CXP 8
PGND 6
S1
S2
OUT 9 R1
MAX1759
BUCK-BOOST CONTROL
R2
SHDN 2
BIAS
1.5MHz OSC
ENABLE FB 10 1.235V
POK 1
N
OUT-LOW
GND 5
1.1V 0.1V
Figure 2. Functional Diagram
_______________________________________________________________________________________
7
Buck/Boost Regulating Charge Pump in MAX MAX1759
Capacitor Selection
Optimize the charge-pump circuit for physical size, output current, and output ripple by selecting capacitors CIN, CX, and COUT. See Table 1 for suggested capacitor values. Note that capacitors must have low ESR (20m) to maintain low output ripple. Ceramic capacitors are recommended. In cost-sensitive applications where high output current is needed, the output capacitor may be a combination of a 1F ceramic in parallel with a 10F tantalum capacitor. The ceramic capacitor's low ESR will help keep output ripple within acceptable levels.
0.33F
CXN
CXP OUT
VOUT = 2.5V
VIN = 1.6V TO 5.5V IN 10F
10F 100k
MAX1759
POK
Output Voltage Ripple
The MAX1759 proprietary control scheme automatically chooses between voltage doubling and voltage stepdown to maintain output voltage regulation over various load currents and VIN to VOUT voltage differentials. When VIN is lower than VOUT, the charge pump always operates in voltage-doubler mode. It regulates the output voltage by modulating the charge delivered by the transfer capacitor. When VIN is higher than VOUT, the charge pump operates in voltage step-down mode, but may revert to voltage-doubler mode if necessary to maintain regulation under load. While operating in step-down mode, the output voltage ripple is typically much lower than it is in voltage-doubler mode (see Typical Operating Characteristics).
SHDN FB GND PGND
R1 76.8k
R2 75k
Figure 3. Using External Feedback for Regulated 2.5V Output
Table 1. Capacitor Selection
OUTPUT CURRENT (mA) 100 100 50 CAPACITOR VALUE CIN (F) 10 4.7 2.2 CX (F) 0.33 0.22 0.1 COUT (F) 10 4.7 2.2 OUTPUT RIPPLE (mV) VIN = 2.5V 40 80 100 VIN = 4.2V 20 60 80
Output Current
The MAX1759 is guaranteed to deliver a regulated 3.3V at 100mA continuous, from a +2.5V input. Peaks up to 200mA are acceptable as long as the current is 100mA (RMS).
Applications Information
PC Board Layout
The MAX1759 is a high-frequency switched-capacitor voltage regulator. For best circuit performance, use a ground plane and keep CIN, CX, COUT, and feedback resistors (if used) close to the device. If using external feedback, keep the feedback node as small as possible by positioning the feedback resistors very close to FB. Suggested PC component placement and board layout are shown in Figures 4a and 4b.
Chip Information
TRANSISTOR COUNT: 1802
8
_______________________________________________________________________________________
Buck/Boost Regulating Charge Pump in MAX MAX1759
POK
POK
SHDN VIN C1
R3 R2 R1 VOUT U1
SHDN VIN VOUT
C3 C2 GND PLANE
GND PLANE
Figure 4a. MAX1759 Component Placement Guide
Figure 4b. MAX1759 Recommended PC Board Layout
_______________________________________________________________________________________
9
Buck/Boost Regulating Charge Pump in MAX MAX1759
Package Information
10LUMAX EPS
Note: The MAX1759 does not have an exposed pad.
10
______________________________________________________________________________________
Buck/Boost Regulating Charge Pump in MAX MAX1759
NOTES
______________________________________________________________________________________
11
Buck/Boost Regulating Charge Pump in MAX MAX1759
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, 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 MAX1759

	To Download MAX1759 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .