MAXIM MAX1715 User Manual

For price, delivery, and to place orders, please contact Maxim Distribution at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

General Description

The MAX1715 PWM controller provides the high efficiency, excellent transient response, and high DC output accuracy needed for stepping down high-voltage batteries to generate low-voltage CPU core, I/O, and chipset RAM supplies in notebook computers.

Maxim’s proprietary Quick-PWM™ quick-response, constant-on-time PWM control scheme handles wide input/output voltage ratios with ease and provides 100ns “instant-on” response to load transients while maintaining a relatively constant switching frequency.

The MAX1715 achieves high efficiency at a reduced cost by eliminating the current-sense resistor found in traditional current-mode PWMs. Efficiency is further enhanced by its ability to drive very large synchronousrectifier MOSFETs.

Single-stage buck conversion allows this device to directly step down high-voltage batteries for the highest possible efficiency. Alternatively, two-stage conversion (stepping down the +5V system supply instead of the battery) at a higher switching frequency allows the minimum possible physical size.

The MAX1715 is intended for CPU core, chipset, DRAM, or other low-voltage supplies as low as 1V. The MAX1715 is available in a 28-pin QSOP package. For applications requiring VID compliance or DAC control of output voltage, refer to the MAX1710/MAX1711 data sheet. For a single-output version, refer to the MAX1714 data sheet.

Applications

Notebook Computers

CPU Core Supply

Chipset/RAM Supply as Low as 1V

1.8V and 2.5V I/O Supply

Features

♦ Ultra-High Efficiency

♦ No Current-Sense Resistor (lossless I

LIMIT

)

♦ Quick-PWM with 100ns Load-Step Response

♦ 1% V

OUT

Accuracy over Line and Load

♦ Dual-Mode Fixed 1.8V/3.3V/Adj or 2.5V/Adj Outputs

♦ Adjustable 1V to 5.5V Output Range

♦ 2V to 28V Battery Input Range

♦ 200/300/420/540kHz Nominal Switching Frequency

♦ Over/Undervoltage Protection

♦ 1.7ms Digital Soft-Start

♦ Drives Large Synchronous-Rectifier FETs

♦ Power-Good Indicator

MAX1715

Ultra-High Efficiency, Dual Step-Down

Controller for Notebook Computers

________________________________________________________________ Maxim Integrated Products 1

19-1541; Rev 2; 8/05

Pin Configuration appears at end of data sheet.

Quick-PWM is a trademark of Maxim Integrated Products.

Ordering Information

EVALUATION KIT

AVAILABLE

OUTPUT1

1.8V

BATTERY

4.5V TO 28V

ILIM1

ON2

DL1

TON

OUT1

LX1

DH1

FB1 AGND

BST1

ILIM2 ON1

REF

DL2

PGND

OUT2

LX2

DH2

FB2

V+

BST2

SKIP

5V INPUT

PGOOD

OUTPUT2

2.5V

MAX1715

Minimal Operating Circuit

PART TEMP RANGE PIN-PACKAGE

MAX1715EEI -40°C to +85°C 28 QSOP

MAX1715EEI+

-40°C to +85°C 28 QSOP

+ Denotes lead-free package.

MAX1715

Ultra-High Efficiency, Dual Step-Down Controller for Notebook Computers

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

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.

V+ to AGND..............................................................-0.3 to +30V

, VCCto AGND..................................................-0.3V to +6V

PGND to AGND or V

to VDD...........................................±0.3V

PGOOD, OUT_ to AGND..........................................-0.3V to +6V

ILIM_, FB_, REF,

SKIP, TON,

ON_ to AGND...........................................-0.3V to (V

+ 0.3V)

DL_ to PGND..............................................-0.3V to (V

+ 0.3V)

BST_ to AGND........................................................-0.3V to +36V

DH1 to LX1 ...............................................-0.3V to (BST1 + 0.3V)

DH2 to LX2 ...............................................-0.3V to (BST2 + 0.3V)

LX1 to BST1..............................................................-6V to +0.3V

LX2 to BST2..............................................................-6V to +0.3V

REF Short Circuit to AGND.........................................Continuous

Continuous Power Dissipation (T

= +70°C)

28-Pin QSOP (derate 8.0mW/°C above +70°C).....640mW/°C

Operating Temperature Range ..........................-40°C to +85°C

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

Storage Temperature Range ............................-65°C to +150°C

Lead Temperature (soldering, 10s) .................................+300°C

ELECTRICAL CHARACTERISTICS

(Circuit of Figure 1, 4A components from Table 1, V

CC = VDD

= +5V, SKIP = AGND, V+ = 15V, TA= 0°C to +85°C, unless otherwise

noted.) (Note 1)

LOAD

= 0 to 4A, each output %0.4

FB2 = GND

Battery voltage, V+

Input Voltage Range

V+ = 24V, OUT2 = 2V

Load Regulation Error

VCC= 4.5V to 5.5V, V+ = 4.5V to 28V

V+ = 24V, OUT1 = 2V

Adjustable mode, each output

Output 2 Error Comparator Threshold (DC Output Voltage Accuracy) (Note 2)

TON = GND

FB_ Input Bias Current

TON = GND

TON = open

OUT

_ = AGND

210 247 280

CONDITIONS

TON = REF

142 173 205

TON = V

OUT_ Input Resistance

µA

Soft-Start Ramp Time

ΩFB_ = AGND

Rising edge of ON_ to full current limit

2.475 2.5 2.525

V+ = 2V to 28V, SKIP = V

, TA = +25°C

LOAD

= 0 to 4A

V+ = 2V to 28V, SKIP = V

, TA = +25°C

LOAD

= 0 to 4A

154 182 215

On-Time (PWM2)

112 136 160

0.99 1.00 1.01

On-Time (PWM1)

1.7

0.99 1.00 1.01

300 353 407

1.782 1.8 1.818

-0.1 0.1

TON = open

292 336 380

TON = REF

75k

3.267 3.3 3.333

FB1 = V

FB1 = AGND

FB1 = OUT1

228

FB2 = OUT2

1 5.5

Output Voltage Range

%0.2

198 234 270

Line Regulation Error

TON = V

420 484 550

UNITSMIN TYP MAXPARAMETER

Output 1 Error Comparator Threshold (DC Output Voltage Accuracy) (Note 2)

4.5 5.5

DD,VCC

Output 1 Error Comparator Threshold (DC Output Voltage Accuracy) (Note 2)

V+ = 2V to 28V, SKIP = V

, TA = 0°C to +85°C

LOAD

= 0 to 4A

0.985 1.00 1.105

1.773 1.8 1.827

3.250 3.3 3.350

FB1 = V

FB1 = AGND

FB1 = OUT1

FB2 = GND

Output 2 Error Comparator Threshold (DC Output Voltage Accuracy) (Note 2)

2.463 2.5 2.538

V+ = 2V to 28V, SKIP = V

, TA = 0°C to +85°C

LOAD

= 0 to 4A

0.985 1.00 1.105

FB2 = OUT2

MAX1715

Ultra-High Efficiency, Dual Step-Down

Controller for Notebook Computers

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(Circuit of Figure 1, 4A components from Table 1, V

CC = VDD

= +5V, SKIP = AGND, V+ = 15V, TA= 0°C to +85°C, unless otherwise

noted.) (Note 1)

(Note 3) ns400 500Minimum Off-Time

REF

= 0 to 50µA

No external REF load

ON1 = ON2 = 0

V2 0.01Reference Load Regulation

V1.98 2 2.02Reference Voltage

µA<1 5Shutdown Supply Current (V+)

µA<1 5

Shutdown Supply Current (VCC+ VDD)

Falling edge, hysteresis = 40mV V1.6REF Fault Lockout Voltage

PGND - LX_, I

LIM

resistor = 100kΩ

40 50 60

Current-Limit Threshold (Positive Direction, Adjusted)

PGND - LX_, TA= +25°C, I

LIM

= V

mV-145 -120 -95

Current-Limit Threshold (Negative Direction)

PGND - LX_, SKIP = AGND

mV-5 3 10

Current-Limit Threshold, Zero Crossing

Hysteresis = 10°C °C150Thermal Shutdown Threshold

Rising edge, hysteresis = 20mV, PWM disabled below this level

V4.1 4.4

VCCUndervoltage Lockout Threshold

BST - LX forced to 5V Ω1.5 5DH Gate Driver On-Resistance

FB1 and FB2 forced above the regulation point µA1100 1600

Quiescent Supply Current (VCC+ VDD)

µA25 70Quiescent Battery Current (V+)

FB_ forced 2% above trip threshold µs1.5

Overvoltage Fault Propagation Delay

With respect to error comparator threshold %8.5 10.5 13Overvoltage Trip Threshold

With respect to error comparator threshold %60 70 80Output Undervoltage Threshold

From ON_ signal going high ms10 20 30

Output Undervoltage Lockout Time

PGND - LX_, I

LIM

= V

mV75 100 125

Current-Limit Threshold (Positive Direction, Fixed)

ON1 = ON2 = 0

DL, high state Ω1.5 5

DL Gate Driver On-Resistance (pull-up)

0.6 2.5

DH Gate Driver Source/Sink Current

DH forced to 2.5V, BST_ - LX_ forced to 5V 1

ADL Gate Driver Source Current DL forced to 2.5V 1

ADL Gate Driver Sink Current DL forced to 2.5V 3

nsDead Time

DL rising 35

REF in regulationREF Sink Current

DL, low state

DL Gate Driver On-Resistance (pull-down)

µA

CONDITIONS UNITSMIN TYP MAXPARAMETER

PGND - LX_, I

LIM

resistor = 400kΩ 160 200 240

DH rising 26

ON_, SKIP

0.8

VLogic Input High Voltage

ON_, SKIP

2.4 VLogic Input Low Voltage

MAX1715

Ultra-High Efficiency, Dual Step-Down Controller for Notebook Computers

4 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS

(Circuit of Figure 1, 4A components from Table 1, V

CC = VDD

= +5V, SKIP = AGND, V+ = 15V, TA= -40°C to +85°C, unless otherwise

noted.) (Note 1)

ELECTRICAL CHARACTERISTICS (continued)

(Circuit of Figure 1, 4A components from Table 1, V

CC = VDD

= +5V, SKIP = AGND, V+ = 15V, TA= 0°C to +85°C, unless otherwise

noted.) (Note 1)

CONDITIONS

level

VCC- 0.4

TON Threshold

Float level 3.15 3.85

REF level 1.65 2.35

AGND level 0.5

TON (0 or VCC) µA-3 3Logic Input Current

UNITSMIN TYP MAXPARAMETER

On-Time (PWM1)

112 136 160

FB2 = GND

FB2 = OUT2

V+ = 4.5V to 28V, SKIP = V

3.234 3.3 3.372FB1 = V

FB1 = AGND

FB1 = OUT1

1.764 1.8 1.836

Minimum Off-Time 400 500 ns(Note 3)

2.45 2.5 2.55

Output 2 Error Comparator Threshold (DC Output Voltage Accuracy) (Note 2)

0.98 1.00 1.02 V

PARAMETER MIN TYP MAX UNITS

Input Voltage Range

228

4.5 5.5

Output 1 Error Comparator Threshold (DC Output Voltage Accuracy) (Note 2)

0.98 1.00 1.02

CONDITIONS

Battery voltage, V+

DD, VCC

V+ = 2V to 28V, SKIP = V

On-Time (PWM2)

154 182 215

ON_, SKIP (0 or VCC)

µA-1 1Logic Input Current

Falling edge, FB_ forced 2% below PGOOD trip threshold µs1.5PGOOD Propagation Delay

Measured at FB_, with respect to error comparator threshold, no load

%-8 -5.5 -4PGOOD Trip Threshold

SINK

= 1mA V0.1 0.4PGOOD Output Low Voltage

High state, forced to 5.5V µA1PGOOD Leakage Current

SKIP, to deactivate OVP circuitry

mA-5 -1Logic Input Current

210 247 280

142 173 205

300 353 407

292 336 380

198 234 270

V+ = 24V, OUT2 = 2V

420 484 550

TON = GND

TON = REF

TON = open

TON = V

V+ = 24V, OUT1 = 2V

TON = GND

TON = REF

TON = open

TON = V

MAX1715

Ultra-High Efficiency, Dual Step-Down

Controller for Notebook Computers

_______________________________________________________________________________________ 5

0.01 1010.1

100

MAX1715-01

LOAD CURRENT (A)

EFFICIENCY (%)

EFFICIENCY vs. LOAD CURRENT

(1.8V, 4A COMPONENTS, SKIP = GND)

V+ = +7V

V+ = +12V

V+ = +20V

0.01 1010.1

100

MAX1715-02

LOAD CURRENT (A)

EFFICIENCY (%)

EFFICIENCY vs. LOAD CURRENT

(1.8V, 4A COMPONENTS, SKIP = V

)

V+ = +7V

V+ = +20V

V+ = +12V

0.01 1010.1

100

MAX1715-03

LOAD CURRENT (A)

EFFICIENCY (%)

EFFICIENCY vs. LOAD CURRENT

(2.5V, 4A COMPONENTS, SKIP = GND)

V+ = +7V

V+ = +20V

V+ = +12V

Note 1: Specifications to -40°C are guaranteed by design, and not production tested. Note 2: When the inductor is in continuous conduction, the output voltage will have a DC regulation higher than the trip level by

50% of the ripple. In discontinuous conduction (SKIP = AGND, light load) the output voltage will have DC regulation higher than the trip level by approximately 1.5% due to slope compensation.

Note 3: On-time and off-time specifications are measured from the 50% point at the DH pin with LX = PGND, V

BST

= 5V. Actual

in-circuit times may differ due to MOSFET switching speeds.

__________________________________________Typical Operating Characteristics

(Circuit of Figure 1, components from Table 1, VIN= +15V, SKIP = AGND, TON = unconnected, TA= +25°C, unless otherwise noted.)

ELECTRICAL CHARACTERISTICS (continued)

(Circuit of Figure 1, 4A components from Table 1, V

CC = VDD

= +5V, SKIP = AGND, V+ = 15V, TA= -40°C to +85°C, unless otherwise

noted.) (Note 1)

Quiescent Battery Current (V+) 25 70 µA

Reference Voltage 1.97 2 2.03 VNo external REF load

Quiescent Supply Current (VCC+ VDD)

1100 1600 µAFB1 and FB2 forced above the regulation point

PARAMETER MIN TYP MAX UNITSCONDITIONS

Reference Load Regulation 0.01 VI

REF

= 0 to 50µA

Overvoltage Trip Threshold 10 12.5 15 %With respect to error comparator threshold

Output Undervoltage Threshold 60 70 80 %With respect to error comparator threshold

Current-Limit Threshold (positive direction, fixed)

75 100 125 mVPGND - LX_, I

LIM

= V

Current-Limit Threshold (positive direction, adjusted)

32 50 62

PGND - LX_, I

LIM

resistor = 100kΩ

PGND - LX_, I

LIM

resistor = 400kΩ 160 200 240

Thermal Shutdown Threshold 150 °CHysteresis = 10°C

Rising edge, hysteresis = 20mV, PWM disabled below this level

4.1 4.4 V

VCCUndervoltage Lockout Threshold

Logic Input High Voltage 2.4 V

ON_, SKIP ON_, SKIP

0.8 VLogic Input Low Voltage

SKIP, to deactivate OVP circuitry

-5 -1 mALogic Input Current

MAX1715

Ultra-High Efficiency, Dual Step-Down Controller for Notebook Computers

6 _______________________________________________________________________________________

_____________________________Typical Operating Characteristics (continued)

(Circuit of Figure 1, components from Table 1, VIN= +15V, SKIP = AGND, TON = unconnected, TA= +25°C, unless otherwise noted.)

0.01 1010.1

100

MAX1715-9

LOAD CURRENT (A)

EFFICIENCY (%)

EFFICIENCY vs. LOAD CURRENT

(1.3V, 8A COMPONENTS, SKIP = V

)

V+ = +7V

V+ = +20V

V+ = +12V

0.01 1010.1

300

400

200

100

MAX1715-10

LOAD CURRENT (A)

FREQUENCY (kHz)

FREQUENCY vs. LOAD CURRENT

(4A COMPONENTS)

OUT1, SKIP = V

OUT2, SKIP = V

OUT1, SKIP = GND

OUT2, SKIP = GND

400

300

200

100

4128 162024

MAX1715-11

SUPPLY VOLTAGE (V)

FREQUENCY (kHz)

FREQUENCY vs. SUPPLY VOLTAGE

(4A COMPONENTS, SKIP = V

)

OUT1

OUT2

100

0.001 0.1 10.01 10

MAX1715-07

LOAD CURRENT (A)

EFFICIENCY (%)

EFFICIENCY vs. LOAD CURRENT

(3.3V, 1.5A COMPONENTS, V

= 5V)

SKIP = V

SKIP = GND

0.01 1010.1

100

MAX1715-08

LOAD CURRENT (A)

EFFICIENCY (%)

EFFICIENCY vs. LOAD CURRENT

(1.3V, 8A COMPONENTS, SKIP = GND)

V+ = +7V

V+ = +20V

V+ = +12V

0.01 1010.1

100

MAX1715-04

LOAD CURRENT (A)

EFFICIENCY (%)

EFFICIENCY vs. LOAD CURRENT

(2.5V, 4A COMPONENTS, SKIP = V

)

V+ = +7V

V+ = +20V

V+ = +12V

0.01 1010.1

100

MAX1715-05

LOAD CURRENT (A)

EFFICIENCY (%)

EFFICIENCY vs. LOAD CURRENT

(5V, 3A COMPONENTS, SKIP = GND)

V+ = +7V

V+ = +20V

V+ = +12V

0.01 1010.1

100

MAX1715-06

LOAD CURRENT (A)

EFFICIENCY (%)

EFFICIENCY vs. LOAD CURRENT

(5V, 3A COMPONENTS, SKIP = V

)

V+ = +7V

V+ = +20V

V+ = +12V

300

200

250

150

100

-400-20

MAX1715-12

TEMPERATURE (°C)

FREQUENCY (kHz)

FREQUENCY vs. TEMPERATURE

(2.5V, 4A COMPONENTS, SKIP = HIGH)

MAX1715-16

A = V

OUT

, 2V/div B = INDUCTOR CURRENT, 2A/div C = DL, 10V/div

START-UP WAVEFORM

(2.5V, 4A COMPONENTS, ACTIVE LOAD)

700

500

600

400

300

100

200

0105

MAX1715-13

INPUT VOLTAGE (V)

SUPPLY CURRENT (μA)

NO-LOAD SUPPLY CURRENT vs. INPUT VOLTAGE

(OUT1 = 1.8V, 4A COMPONENTS;

OUT2 = 2.5V, 4A COMPONENTS; SKIP = GND)

BATT

0105

MAX1715-14

INPUT VOLTAGE (V)

SUPPLY CURRENT (mA)

NO-LOAD SUPPLY CURRENT vs. INPUT VOLTAGE

(OUT1 = 1.8V, 4A COMPONENTS;

OUT2 = 2.5V, 4A COMPONENTS; SKIP = V

)

MAX1715-17

A = V

OUT

, AC-COUPLED, 100mV/div B = INDUCTOR CURRENT, 5A/div C = DL, 10V/div

LOAD-TRANSIENT RESPONSE

(1.3V, 8A COMPONENTS, SKIP = GND)

MAX1715

Ultra-High Efficiency, Dual Step-Down

Controller for Notebook Computers

_______________________________________________________________________________________ 7

_____________________________Typical Operating Characteristics (continued)

(Circuit of Figure 1, components from Table 1, VIN= +15V, SKIP = AGND, TON = unconnected, TA= +25°C, unless otherwise noted.)

MAX1715-19

A = V

OUT

, 2V/div B = INDUCTOR CURRENT, 5A/div C = DL, 10V/div

SHUTDOWN WAVEFORM

(2.5V, 4A COMPONENTS, SKIP = GND)

MAX1715-18

A = V

OUT

, 2V/div B = INDUCTOR CURRENT, 5A/div C = DL, 10V/div

OUTPUT OVERLOAD WAVEFORM

(2.5V, 4A COMPONENTS, SKIP = GND)

MAX1715-15

A = V

OUT

, AC-COUPLED, 100mV/div B = INDUCTOR CURRENT, 2A/div C = DL, 10V/div

LOAD-TRANSIENT RESPONSE

(2.5V, 4A COMPONENTS, SKIP = GND)

170

MAX1715

Ultra-High Efficiency, Dual Step-Down Controller for Notebook Computers

8 _______________________________________________________________________________________

Pin Description

OUT1 ON/OFF Control Input. Drive to AGND to turn OUT1 off. Drive to VCCto turn OUT1 on.

ON110

Feedback Input for OUT1. Connect to AGND for 1.8V fixed output or to VCCfor 3.3V fixed output, or connect to a resistor-divider from OUT1 for an adjustable output.

FB12

+2.0V Reference Voltage Connection. Bypass to AGND with 0.22µF (min) capacitor. Can supply 50µA for external loads.

REF9

Output Voltage Connection for the OUT1 PWM. Connect directly to the junction of the external inductor and output filter capacitors. OUT1 senses the output voltage to determine the on-time and also serves as the feedback input in fixed-output modes.

OUT11

Pulse-Skipping Control Input. Connect to VCCfor low-noise forced-PWM mode. Connect to AGND to enable pulse-skipping operation.

SKIP

Power-Good Open-Drain Output. PGOOD is low when either FB_ input is more than 5.5% below the normal regulation point (typ).

PGOOD7

Analog GroundAGND8

Current-Limit Threshold Adjustment for OUT1. The LX1-PGND current-limit threshold defaults to +100mV if ILIM1 is connected to VCC. Or, connect an external resistor to AGND to adjust the limit. A precision 5µA pull-up current through R

EXT

sets the threshold from 50mV to 200mV. The voltage on the pin is 10 times the current-

limit voltage. Choose R

EXT

equal to 2kΩ per mV of current-limit threshold (100kΩ to 400kΩ).

ILIM13

Battery Voltage Sense Connection. Connect to the input power source. V+ is used only to set the PWM oneshot timing.

V+4

On-Time Selection Control Input. This is a four-level input used to determine DH_ on-time. The TON table below is for VIN= 24V, V

OUT1

= 1.8V, V

OUT2

= 2.5V condition.

TON5

FUNCTIONNAME

OUT2 ON/OFF Control Input. Drive to AGND to turn OUT2 off. Drive to VCCto turn OUT2 on.

ON211

Current-Limit Threshold Adjustment for OUT2. The LX2-PGND current-limit threshold defaults to +100mV if ILIM2 is connected to VCC. Or, connect an external resistor to AGND to adjust the limit. A precision 5µA pull-up current through R

EXT

sets the threshold from 50mV to 200mV. The voltage on the pin is 10 times the current-

limit voltage. Choose R

EXT

equal to 2kΩ per mV of current-limit threshold (100kΩ to 400kΩ).

ILIM212

Feedback Input for OUT2. Connect to AGND for 2.5V fixed output, or connect to a resistor-divider from OUT2 for an adjustable output.

FB213

Output Voltage Connection for the OUT2 PWM. Connect directly to the junction of the external inductor and output filter capacitors. OUT2 senses the output voltage to determine the on-time and also serves as the feedback input in fixed-output mode.

OUT214

No Connection. These pins are not connected to any internal circuitry. Connect the N.C. pins to the ground plane to enhance thermal conductivity.

N.C.

15, 23,

AGND

TON

Open V

REF

235

345

485

620

Frequency (OUT1) (kHz) Frequency (OUT2) (kHz)

460 355 255 170

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