MPS MP1591 User Manual

MP1591

The Future of Analog IC Technology

DESCRIPTION

The MP1591 is a high voltage step-down converter ideal for automotive power adapter battery chargers. Its wide 6.5V to 32V input voltage range covers the automotive battery’s requirements and it achieves 2A continuous output for quick charge capability.

Current mode operation provides fast transient response and eases loop stabilization. Fault protection includes cycle-by-cycle current limiting and thermal shutdown. In shutdown mode, the converter draws only 20A of supply current.

The MP1591 requires a minimum number of readily available external components to complete a 2A step-down DC to DC converter solution.

EVALUATION BOARD REFERENCE

Board Number Dimensions

EV0020 2.1”X x 1.4”Y x 0.5”Z

2A, 32V, 330KHz

Step-Down Converter

FEATURES

• Wide 6.5V to 32V Input Operating Range

• 34V Absolute Maximum Input

• 2A Output Current

• 120m Internal Power MOSFET Switch

• Stable with Low ESR Output Ceramic

Capacitors

• Up to 95% Efficiency

• 20A Shutdown Mode

• Fixed 330KHz Frequency

• Thermal Shutdown

• Cycle-by-Cycle Over Current Protection

• Output Adjustable From 1.23V to 21V

• Under Voltage Lockout

• Reference Voltage Output

• Available in 8-Pin SOIC Packages

APPLICATIONS

• Automotive Power Adapters

• PDA and Cellular Phone Battery Chargers

• Distributed Power Systems

• Automotive Aftermarket Electronics

TYPICAL APPLICATION

INPUT

6.5V to 32V

OFF ON

OPEN

NOT USED

MP1591

REF

GND COMP

OPEN

BSIN

4.7nF

10nF

“MPS” and “The Future of Analog IC Technology” are Registered Trademarks of Monolithic Power Systems, Inc.

Efficiency vs Load Current

100

=5V

OUT

=3.3V

OUTPUT

2.5V 2A

EFFICIENCY (%)

0 0.5 1 1.5 2

OUT

VIN=12V

LOAD CURRENT (A)

MP1591 – 2A, 32V, 330KHz STEP-DOWN CONVERTER

PACKAGE REFERENCE

TOP VIEW

GND

EXPOSED PAD

ON BACKSIDE

(SOIC8N ONLY)

CONNECT TO PIN 4

Part Number* Package Temperature

MP1591DN SOIC8E

MP1591DS SOIC8

For Tape & Reel, add suffix –Z (eg. MP1591DN–Z)

For RoHS Compliant Packaging, add suffix –LF (eg. MP1591DN–LF–Z)

REF

COMP

–40°C to +85°C –40°C to +85°C

ABSOLUTE MAXIMUM RATINGS

(1)

IN Supply Voltage........................ –0.3V to +34V

SW Voltage............................. –1V to V

BS Voltage

....................VSW – 0.3V to VSW + 6V

+ 0.3V

All Other Pins................................. –0.3V to +6V

Junction Temperature............................... 150°C

Lead Temperature .................................... 260°C

Storage Temperature ..............–65°C to +150°C

Recommended Operating Conditions

(2)

Input Voltage ................................... 6.5V to 32V

Operating Temperature .............–40°C to +85°C

Thermal Resistance

(3)

θJC

SOIC8 (w/ Exposed Pad) ....... 50 ...... 10... °C/W

SOIC8..................................... 90 ...... 45... °C/W

Notes:

1) Exceeding these ratings may damage the device.

2) The device is not guaranteed to function outside of its operating conditions.

3) Measured on approximately 1” square of 1 oz copper.

ELECTRICAL CHARACTERISTICS

VIN = 12V, TA = +25°C, unless otherwise noted.

Parameter Symbol Condition Min Typ Max Units

Shutdown Supply Current VEN = 0V 20 35 A

Supply Current VEN = 5V, VFB = 1.4V 1.0 1.2 mA

Feedback Voltage

6.5V ≤ V

≤ 32V, V

COMP

< 2V

Error Amplifier Voltage Gain 400 V/V

Error Amplifier Transconductance

High-Side Switch On Resistance

Low-Side Switch On Resistance

(4)

120

(4)

8.5

ΔI

= ±10A

High-Side Switch Leakage Current VEN = 0V, VSW = 0V 0 10 A

Current Limit

Current Sense to COMP Transconductance

(5)

2.5 3.6 4.9 A

3.5 A/V

Oscillation Frequency 280 330 380 KHz

Short Circuit Oscillation Frequency VFB = 0V 35 KHz

Maximum Duty Cycle

Minimum Duty Cycle

(4)

= 1.0V 90 %

= 1.5V 0 %

EN Shutdown Threshold Voltage 0.8 1.2 1.6 V

Enable Pull-Up Current VEN = 0V 1.8 A

EN UVLO Threshold VEN Rising 2.4 2.6 2.8 V

EN UVLO Threshold Hysteresis 250 mV

1.202 1.230 1.258 V

500 700 1100 A/V

mΩ

Ω

MP1591 – 2A, 32V, 330KHz STEP-DOWN CONVERTER

ELECTRICAL CHARACTERISTICS (continued)

VIN = 12V, TA = +25°C, unless otherwise noted.

Parameter Symbol Condition Min Typ Max Units

Thermal Shutdown

REF Voltage I

REF Load Regulation

REF Line Regulation

Notes:

4) These parameters are guaranteed by design, not production tested.

5) Equivalent output current = 1.5A  50% Duty Cycle

2.0A  50% Duty Cycle Assumes ripple current = 30% of load current. Slope compensation changes current limit.

(4)

160

= 0 5.0 V

(4)

I

(4)

REF

= 0 to 1mA 100 mV

REF

= 100A, VIN = 6.5 to 32V 30 mV

REF

°C

PIN FUNCTIONS

Pin # Name Description

1 BS High-Side Gate Drive Boost Input. BS supplies the drive for the high-side N-Channel MOSFET

switch. Connect a 10nF or greater capacitor from SW to BS to power the high-side switch.

2 IN Power Input. IN supplies the power to the IC, as well as the step-down converter switches.

Drive IN with a 6.5V to 32V power source. Bypass IN to GND with a suitably large capacitor to

eliminate noise on the input to the IC. See Input Capacitor.

3 SW Power Switching Output. SW is the switching node that supplies power to the output. Connect

the output LC filter from SW to the output load. Note that a capacitor is required from SW to BS to power the high-side switch.

4 GND Ground. For the MP1591DN, connect the Exposed Pad to pin 4.

5 FB Feedback Input. FB senses the output voltage to regulate that voltage. Drive FB with a resistive

voltage divider from the output voltage. The feedback threshold is 1.230V. See Setting the Output Voltage.

6 COMP Compensation Node. COMP is used to compensate the regulation control loop. Connect a

series RC network from COMP to GND to compensate the regulation control loop. In some

cases, an additional capacitor from COMP to GND is required. See Compensation.

7 EN Enable/UVLO. A voltage greater than 2.8V enables operation. For complete low current

shutdown the EN pin voltage needs to be less than 800mV.

8 REF Reference Output. REF is the 5V reference voltage output. It can supply up to 1mA to external

circuitry. If used, bypass REF to GND with 10nF or greater capacitor. Leave REF unconnected if not used.

MP1591 – 2A, 32V, 330KHz STEP-DOWN CONVERTER

OPERATION

The MP1591 is a current mode step-down regulator. It regulates input voltages from 6.5V to 32V down to an output voltage as low as

1.230V and is able to supply up to 2A of load current.

The MP1591 uses current-mode control to regulate the output voltage. The output voltage is measured at FB through a resistive voltage divider and amplified through the internal error amplifier. The output current of the transconductance error amplifier is presented at COMP where a network compensates the regulation control system.

REF

1.2V

2.60V/

2.35V

INTERNAL

REGULATORS

SHUTDOWN

COMPARATOR

LOCKOUT

COMPARATOR

OSCILLATOR

35/330KHz

SLOPE

COMP

CLK

The voltage at COMP is compared to the switch current measured internally to control the output voltage. The converter uses an internal N-Channel MOSFET switch to step-down the input voltage to the regulated output voltage. Since the MOSFET requires a gate voltage greater than the input voltage, a boost capacitor connected between SW and BS drives the gate. The capacitor is internally charged while SW is low. An internal 10 switch from SW to GND is used to insure that SW is pulled to GND when the switch is off to fully charge the BS capacitor

CURRENT

SENSE

AMPLIFIER

CURRENT

-COMPARATOR

SRQ

1.8V

GND

THERMAL

PROTECTION

ERROR

AMPLIFIER

COMP

FREQUENCY

FOLDBACK

COMPARATOR

1.230V0.7V

Figure 1—Functional Block Diagram

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MPS MP1591 User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual