Preliminary Technical Data Precision Switchable Vout Regulator for OTP Applications FCDC 00159 FEATURES Output Voltage Switchable between 2.5V 2% and 7.0V 1% Output Current: 0 to 50 mA Input voltage: 3.2 V to 5.25V Ripple 2% ppk of Output Voltage DESCRIPTION: OTP POWER REFERENCE DESIGN USING ADP1610, ADP1710 AND ADR550 • This OTP Power Reference design is a switchable output voltage regulator. It provides 2.5V during normal operation and 7.0V +/- 1% for One Time Programming. • The 2.5V is regulated by an adjustable ADP1710 LDO with output through a Schottky series blocking diode. • The 7.0V output uses an ADP1610 boost regulator with a DC blocking charge pump to allow the output to drop to 0 volts when the boost is not running. It also uses an ADR550 reference in the feedback path to provide superior set point accuracy. • Input voltage is 3.3V to 5.0V • Output current is 0 to 40 mA. 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Preliminary Technical Data FCDC 00159 TABLE OF CONTENTS Features....................................................................................................................................................................................................... 1 Description: OTP Power reference design using ADP1610, ADP1710 and ADR550..................................................................... 1 Revision History........................................................................................................................................................................................ 2 General Description ................................................................................................................................................................................. 3 ADP1610................................................................................................................................................................................................ 3 ADP1710................................................................................................................................................................................................ 3 ADR550.................................................................................................................................................................................................. 3 Block Diagram........................................................................................................................................................................................... 4 Schematic ................................................................................................................................................................................................... 5 Bill of Materials ......................................................................................................................................................................................... 6 Sample Output Waveforms...................................................................................................................................................................... 7 TABLE OF FIGURES Figure 1. Block Diagram of the Switchable Vout Regulator .......................................................................................................... 4 Figure 2. Schematic Diagram of the Switchable Vout Regulator .................................................................................................. 5 Figure 3. Transition from 2.5V to 7.0V Output with No Load and 5.0 VDC input................................................................... 7 Figure 4. Transition from 7.0V to 2.5V Output with No Load and 5.0 VDC input................................................................... 7 Figure 5. Transition from 2.5V to 7.0V Output with 40 mA Load and 5.0 VDC input ............................................................ 7 Figure 6. Transition from 7.0V to 2.5V Output with 40 mA Load and 5.0 VDC input ............................................................ 7 Figure 7. Transition from 2.5V to 7.0V Output with No Load and 3.3 VDC input................................................................... 8 Figure 8. Transition from 7.0V to 2.5V Output with No Load and 3.3 VDC input................................................................... 8 Figure 9. Transition from 2.5V to 7.0V Output with 40 mA Load and 3.3 VDC input ............................................................ 8 Figure 10. Transition from 7.0V to 2.5V Output with 40 mA and 3.3 VDC input.................................................................. 8 REVISION HISTORY 10/09/2008—Revision 1: Initial Version Rev. 1 | Page 2 of 9 Preliminary Technical Data FCDC 00159 GENERAL DESCRIPTION ADP1610 The ADP1610 is a dc-to-dc step-up switching converter with an integrated 12V 1.2 A, 0.2 Ω power switch. It operates using current mode pulse-width modulation (PWM). The ADP1610 has a Soft Start pin. Typical applications use a capacitor from the soft start pin to ground to slow the rate of rise of the error amplifier output at power up. This limits the regulator inrush current. In this application, the ADR550 reference in the feedback path significantly changes the feedback loop dynamics, and we are most concerned with limiting overshoot of the 7V output on power-up. We control this by limiting the voltage rate-of-rise using a series RC bypass in parallel with the ADR550 reference. This technique works best with no capacitor at the soft start pin. A normal boost regulator has no ability to block current flow from the input through the diode and inductor to the output. In this application, this normal boost "pass-through" is unacceptable. DC blocking is needed so that Vout can be controlled by the LDO when the boost regulator is not working. For that reason, we insert a DC blocking capacitor-diode charge pump ahead of the boost output diode. This causes the Vout to settle to the LDO output voltage when the boost is not running. This modification reduces the output current capability of the boost regulator, however the 40 mA requirement is far below the normal capability of the ADP1610 and the charge pump is appropriate for this application. ADP1710 The ADP1710 is a low dropout linear regulator that operates from 2.5 V to 5.5 V and provides up to 150 mA of output current. It is available in sixteen fixed output voltage options and an adjustable version, which is the one chosen for this application. In this application , the ADP1710 output is isolated from the 7V output using a Schottky series output blocking diode. For extra protection of the LDO we have a second diode added antiparallel from LDO output to input. Using the adjustable version ADP1710 with suitable resistor stuffing options allows the LDO to regulate 2.5V at either the anode or the cathode of the series output blocking diode. ADR550 The ADR520/ADR525/ ADR530/ADR540/ADR550 are high precision shunt voltage references that are set for 2.048 V, 2.5 V, 3.0 V, 4.096 V, and 5.0 V respectively. They are available in either SC70 and SOT-23-3 packages. These references feature low temperature drift of 40 ppm/°C, an initial accuracy of better than ±0.2%, and ultralow output noise of 14 μV peakpeak. The advanced design of the ADR520/ADR525/ ADR530/ADR540/ADR550 eliminates the need for compensation by an external capacitor, but they are stable with any capacitive load. They are specified over an operating current range of 50 μA up to 15 mA. This low operating current and ease of use make these references ideally suited for handheld, battery-powered applications. This application uses the 5.0V ADR550 in the feedback loop divider of the ADP1610 in order to provide 1% output voltage accuracy. We operate the ADR550 at 1.23V / 3.01K ohms, which gives us about 400 uA. This allows a wide margin relative to both the minimum and maximum operating current of the ADR550. Rev. 1 | Page 3 of 9 Preliminary Technical Data FCDC 00159 BLOCK DIAGRAM Figure 1. Block Diagram of the Switchable Vout Regulator Rev. 1 | Page 4 of 9 Preliminary Technical Data FCDC 00159 SCHEMATIC Figure 2. Schematic Diagram of the Switchable Vout Regulator Rev. 1 | Page 5 of 9 Preliminary Technical Data FCDC 00159 BILL OF MATERIALS Table 1. Bill of Materials for the Switchable Vout Regulator design. Description IC Boost Regulator ADP1611 IC Reference ADR550ARTZ IC Adjustable LDO ADP1710AUJZ 2.2 nF X7R 0603 25V Open Capacitor 10 uF X5R 1210 Ceramic Open 2.2 uF 6.3V 0603 X5R 2.2 uF 6.3V 0603 X5R Capacitor 10 uF X5R 1210 Ceramic Capacitor 10 uF X5R 1210 Ceramic Capacitor 10 uF X5R 1210 Ceramic 100 nF 16V 0603 X7R 1 uF 6.3V 0603 X5R Open Open Diode Schottky 1A 30V Diode Schottky 1A 30V Diode Schottky 1A 30V Diode Schottky 1A 30V Inductor shielded 22 uH Inductor unshielded 1 uH Resistor 24K 5% 0603 Resistor 3.01K 0.1% 0603 Open Resistor 140K 1% 0603 Resistor 1.91K 0.1% 0603 Open Resistor 0 Ohms 0603 Resistor 2K 5% 0603 Open Resistor 10.0K 1% 0603 Open Resistor 21.5K 1% 0603 Open Open Designator U1 U3 U4 C2 C3 C4 C5 C6 C7 C8 C9 C10 C12 C13 C15 C18 D1 D2 D3 D4 L1 L2 R2 R8 R9 R10 R11 R13 R14 R15 R16 R17 R18 R19 R23 R25 Manufacturer MFR# Analog Devices, Inc. Analog Devices, Inc. Analog Devices, Inc. Generic ADP1611 ADR550ARTZ ADP1710AUJZ Generic Murata GRM31CR61A106KA01L Generic Generic Murata Murata Murata Generic Generic Generic Generic GRM31CR61A106KA01L GRM31CR61A106KA01L GRM31CR61A106KA01L Generic Generic On Semi On Semi On Semi On Semi Coilcraft Coilcraft Generic Generic MBRS130LSFT1 MBRS130LSFT1 MBRS130LSFT1 MBRS130LSFT1 LPS4012-223 ME3220 1 uH Generic Generic Generic Generic Generic Generic Generic Generic Generic Generic Generic Generic Generic Generic Rev. 1 | Page 6 of 9 Preliminary Technical Data FCDC 00159 SAMPLE OUTPUT WAVEFORMS Figure 3. Figure 5. Figure 4. Transition from 2.5V to 7.0V Output with No Load and 5.0 VDC input Transition from 2.5V to 7.0V Output with 40 mA Load and 5.0 VDC input Figure 6. Rev. 1 | Page 7 of 9 Transition from 7.0V to 2.5V Output with No Load and 5.0 VDC input Transition from 7.0V to 2.5V Output with 40 mA Load and 5.0 VDC input Preliminary Technical Data Figure 7. Figure 9. FCDC 00159 Transition from 2.5V to 7.0V Output with No Load and 3.3 VDC input Figure 8. Transition from 2.5V to 7.0V Output with 40 mA Load and 3.3 VDC input Transition from 7.0V to 2.5V Output with No Load and 3.3 VDC input Figure 10. Transition from 7.0V to 2.5V Output with 40 mA and 3.3 VDC input Rev. 1 | Page 8 of 9 Preliminary Technical Data FCDC 00159 NOTES ©2007 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. EB Rev. 1 | Page 9 of 9