Rainbow Electronics MAX8775 User Manual

General Description

The MAX8775 is a dual, step-down, interleaved, fixedfrequency, switch-mode power-supply (SMPS) controller with synchronous rectification. It is intended for GPU cores and I/O power generation in battery-powered systems. Flexible configuration allows the MAX8775 to operate as two independent single-phase regulators, or as one high-current two-phase regulator.

Configured in separate mode, the MAX8775 provides power to two dynamic voltage rails, one for the GPU core and the other for the I/O power rail. Configured in combined mode, the MAX8775 functions as a twophase, high-current, single-output GPU core regulator, powering the high-performance GPU engines used in gaming machines and media center notebooks.

The REFIN voltage setting allows for multiple dynamic output voltages required by the different GPU operating and sleep states. Automatic fault blanking, forced-PWM operation, and transition control are achieved by detecting the voltage change at REFIN. Fixed-frequency operation with 180° out-of-phase interleaving minimizes input ripple current from the lowest input voltages up to the 26V maximum input. Current-mode control allows the use of low-ESR output capacitors. Internal integrators maintain high output accuracy over the full line-and-load range, in both forced-PWM mode and pulse-skipping mode. True differential current sensing provides accurate output current limit and current balance when operated in combined mode. Independent on/off and skip control allows flexible power sequencing and power management. Voltagecontrolled soft-start reduces inrush current. Soft-stop gradually ramps the output voltage down, preventing negative voltage dips.

Applications

2 to 4 Li+ Cells Battery-Powered Devices

Media Center and Gaming Notebooks

GPU and I/O Power Supplies

Tracking Output Power Supplies

Features

o Dual-Output, Fixed-Frequency, Current-Mode

Control

o Combinable Output for Higher Currents o Dynamic Output Voltages with Automatic Fault

Blanking and Transition Control

o True Out-of-Phase Operation o True Differential Current Sense for Accurate

Current Limit and Current Balance

o 4V to 26V Input Range o 100kHz to 600kHz Switching Frequency o 0.5V to 2.5V Adjustable Outputs o Internal Integrator for High Output Accuracy o Stable with Low-ESR Output Capacitors o Independent Selectable PWM and Skip-Mode

Operation

o Independent Power-Good Outputs o Soft-Start and Soft-Stop o 2.5V Precision Reference o < 1µA Typical Shutdown Current

MAX8775

Dual and Combinable Graphics Core

Controller for Notebook Computers

________________________________________________________________

Maxim Integrated Products

Pin Configuration

Ordering Information

19-0670; Rev 0; 11/06

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

EVALUATION KIT

AVAILABLE

Denotes lead-free package.

PART TEMP RANGE

MAX8775ETJ+ -40°C to +85°C

PINPACKAGE

32 Thin QFN 5mm x 5mm

PKG

CODE

T3255-5

TOP VIEW

PGOOD1

DTRANS

SLEW1

DH1

ON1

CSL1

CSH1

SKIP1

BST1

2324 22 20 19 18

OVP1

LX1

DL1

MAX8775

4567

OSC

REFIN1

THIN QFN

5mm x 5mm

PGND

AGND

DL2

REF

LX2

REFIN2

BST2

OVP2

DH2

ON2

CSL2

CSH2

SKIP2

PGOOD2

CCI2

SLEW2

MAX8775

Dual and Combinable Graphics Core Controller for Notebook Computers

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(Circuit of Figure 1, VIN= 12V, SKIP_ = PGND = AGND, ON_ = VCC= 5V, separate mode, TA= 0°C to +85°C, unless otherwise noted. Typical values are at T

= +25°C.)

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.

DD,VCC

, CSH_, CSL_ to AGND............................-0.3V to +6V

ON_, SKIP_, PGOOD_ to AGND ..............................-0.3V to +6V

OVP_, REFIN_ to AGND ...........................................-0.3V to +6V

DTRANS to AGND ....................................................-0.3V to +6V

REF, OSC, SLEW_, CCI2 to AGND ...........-0.3V to (V

+ 0.3V)

BST1, BST2 to AGND .............................................-0.3V to +36V

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

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

DH1 to LX1 ..............................................-0.3V to (V

BST

+ 0.3V)

DH2 to LX2 ..............................................-0.3V to (V

BST2

+ 0.3V)

DL1, DL2 to PGND .....................................-0.3V to (V

+ 0.3V)

AGND to PGND .....................................................-0.3V to +0.3V

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

REF Current ......................................................................+10mA

Continuous Power Dissipation (T

= +70°C) 32-Pin, 5mm x 5mm, Thin QFN

(derate 21.3mW/°C above +70°C).............................1702mW

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

PARAMETER SYM B O L CONDITIONS MIN TYP MAX UNITS

INPUT SUPPLIES

Input Voltage Range

VCC Undervoltage Lockout Threshold V

Quiescent Supply Current (VCC)ICCCSL_ forced above their regulation points 1.5 2.5 mA

Quiescent Supply Current (VDD)I

Shutdown Supply Current (VCC)I

Shutdown Supply Current (VDD)I

SMPS CONTROLLERS

Output Voltage Accuracy

Output Voltage-Adjust Range V

RE FIN Op er ati ng V ol tag e- Ad j ust Rang eV

REFINOK Threshold Either SMPS 0.1 V

REFIN Transient Detection Threshold 5mV (typ) hysteresis ±25 mV

Combined-Mode Enabled Threshold V

DC Load Regulation Either SMPS, SKIP_ = VCC, zero to full load -0.1 %

Line Regulation Error Either SMPS, 4V < VIN < 26V 0.03 %/V

Switching-Frequency Accuracy (Note 3)

Maximum Duty Factor D

Minimum On-Time t

BIASVCC

UVLO

C C (S H D N)

D D (S H D N)

REFIN_

CSL_

REFIN_

REFIN2

OSC

MAX

ONMIN

, V

Rising edge, 50mV typical hysteresis 4.1 4.25 4.5 V

CSL_ forced above their regulation points, SKIP mode

ON1 = ON2 = GND < 1 5 µA

With respect to REFIN_,

REFIN_ = 0.5V to 2.5V,

SKIP_ = V

Either SMPS (Note 2) 0.5 2.5 V

= 143kΩ (f

OSC

= 71.5kΩ (f

OSC

432kΩ (f

(Note 4) 150 ns

OSC

426

4.5 5.5

< 1 5 µA

-5 0 +5 mV

or GND (Note 1)

-1VCC -

= 300kHz nominal) -10 +10

OSC

= 600kHz nominal) to

OSC

= 99kHz nominal)

-15 +15

91 93 %

0.4

MAX8775

Dual and Combinable Graphics Core

Controller for Notebook Computers

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(Circuit of Figure 1, VIN= 12V, SKIP_ = PGND = AGND, ON_ = VCC= 5V, separate mode, TA= 0°C to +85°C, unless otherwise noted. Typical values are at T

= +25°C.)

Idle Mode is a trademark of Maxim Integrated Products, Inc.

SMPS1 to SMPS2 Phase Shift SMPS2 starts after SMPS1

Slew-Rate Current

CURRENT LIMIT

Current-Limit Threshold V

Current-Limit Threshold (Negative)

Current-Limit Threshold (Zero Crossing)

Idle Mode™ Threshold I

REFERENCE (REF)

Reference Voltage V

Refer ence S our ce Load Reg ul ati on ΔV

Reference Sink Load Regulation I

REF Lockout Voltage V

CURRENT BALANCE

Current-Balance Amplifier (GMI) Offset

Current-Balance Amplifier (GMI) Transconductance

FAULT DETECTION

OVP_ Adjust Range V

Outp ut Over vol tag e Tr i p Thr eshol d

Output Overvoltage Fault Propagation Delay

Output Undervoltage Protection Trip Threshold

Output Undevoltage Fault Propagation Delay

Output Undervoltage Protection Blanking Time

PGOOD_ Lower Trip Threshold

PGOOD_ Propagation Delay t

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

50 %

180 Deg

SLEW_

SLEWSS_

LIMIT

NEG

MIN

REF

R E F ( U V L O)

OVP_

OVP

UVP

BLANK

PGOOD

During transition 4.0 4.75 5.5

Startup and shutdown 0.70 0.95 1.20

_ - V

CSH

_ - V

CSH

REFIREF

_ Falling edge, 50mV overdrive 10 µs

_ - V

CSH

_ - V

CSH

VCC = 4.5V to 5.5V,

= 0

REF

= 0µA to 250µA 0.25 1.5 mV

= -50µA 6 mV

REF

Rising edge, hysteresis = 100mV 2.3 V

[V(CSH1,CSL1) - V(CSH2,CSL2)] at I

/Δ[V(CSH1,CSL1) - V(CSH2,CSL2)],

ΔI

CCI

= V

CCI

V(CSH_,CSL_) = -60.0mV to +60.0mV

Rising edge measured at CSL_, with respect to OVP_ set voltage

50mV overdrive 10 µs

Falling edge measured at CSL_, with respect to error comparator threshold

50mV overdrive 10 µs

From rising edge of ON_ 6144 1/f

Falling edge measured at CSL_, with respect to error comparator threshold, hysteresis = 1%

_ 26 30 34 mV

CSL

_ , SKIP_ = V

CSL

_ , SKIP_ = GND 3 mV

CSL

_ , SKIP_ = GND 3.6 6 8.4 mV

CSL

= 0.5V to 2.5V, and

OUT

TA = +25°C to +85°C 2.482 2.50 2.518

= 0°C to +85°C 2.475 2.50 2.525

= 0 -2 +2 mV

CCI

-43 -36 -29 mV

200 µS

0.5 2.5 V

180 200 220 mV

-325 300 -275 mV

-180 -150 -120 mV

µA

MAX8775

Dual and Combinable Graphics Core Controller for Notebook Computers

4 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS (continued)

(Circuit of Figure 1, VIN= 12V, SKIP_ = PGND = AGND, ON_ = VCC= 5V, separate mode, TA= 0°C to +85°C, unless otherwise noted. Typical values are at T

= +25°C.)

(

)

PGOOD_ Output Low Voltage I

PGOOD_ Leakage Current I

PGOOD_ Transition Blanking Time

Current-Balance Fault Comparator Thresholds

Thermal-Shutdown Threshold T

GATE DRIVERS

DH_ Gate Driver On-Resistance R

DL_ Gate Driver On-Resistance (Note 5)

DH_ Gate Driver Source/ Sink Current

DL_ Gate Driver Source Current

DL_ Gate Driver Sink Current I

Dead Time t

Internal Boost Diode Switch R

LX_, BST_ Leakage Current V

INPUTS AND OUTPUTS

Logic Input Current ON1, ON2, DTRANS, SKIP1, SKIP2 -1 +1 µA

Logic Input-High Threshold

Input Leakage Current CSH_, CSL_, 0V, or V

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

= 4mA 0.4 V

SINK

_ High state, PGOOD_ forced to 5.5V 1 µA

PGOOD

Measured from the time CSL_ reaches the

20 µs

SHDN

SOURCE

DL (SINK

DEAD

target voltage based on the slew rate set by C

SLEW_

Lower threshold,

0.84V

V(CCI2, REF),

0.5V

≤ V

≤ 2.5V

Hysteresis = 15°C +160 °C

BST_ - LX_ forced to 5V (Note 5) 1.5 5 Ω

DL_, high state 1.7 5

DL_, low state 0.6 3

DH_ forced to 2.5V, BST_ - LX_ forced to 5V 2 A

DL_ forced to 2.5V 1.7 A

DL_ forced to 2.5V 3.3 A

DL_ to DH_ 15 35

DH_ to DL_ 10 26

Measure with 10mA of current 6.5 9 Ω

_ = VLX_ = 28V < 2 20 µA

BST

ON1, ON2, DTRANS, SKIP1, SKIP2, hysteresis = 225mV

REF

Upper threshold,

1.2V

REF

2.0 2.2

2.9 3.0

1.2 1.7 2.2 V

-0.15 +0.15 µA

MAX8775

Dual and Combinable Graphics Core

Controller for Notebook Computers

_______________________________________________________________________________________ 5

ELECTRICAL CHARACTERISTICS

(Circuit of Figure 1, VIN= 12V, SKIP_ = 0, ON_ = VCC= 5V, separate mode, TA= -40°C to +85°C, unless otherwise noted.) (Note 6)

INPUT SUPPLIES

Input Voltage Range

VCC Undervoltage Lockout

Quiescent Supply Current (VCC)ICCCSL_ forced above their regulation points 2.5 mA

Quiescent Supply Current (VDD)IDDCSL_ forced above their regulation points 5 µA

Shutdown Supply Current (VCC) ON1 = ON2 = GND 5 µA

Shutdown Supply Current (VDD) ON1 = ON2 = GND 5 µA

MAIN SMPS CONTROLLERS

PWM_ Output Voltage

Output Voltage Adjust Range V

REFIN Operating Voltage Adjust Range

Combined Mode Enabled V

Switching Frequency Accuracy (Note 2)

Maximum Duty Factor D

Slew-Rate Current

CURRENT LIMIT

Current-Limit Threshold V

REFERENCE (REF)

Reference Voltage V

Refer ence S our ce Load Reg ul ati on ΔV

Reference Sink Load Regulation I

CURRENT BALANCE

Current-Balance Amplifier (GMI) Offset

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

BIASVCC

UVLO

REFIN_

CSL_

REFIN_

REFIN2

OSC

MAX

SLEW_

SLEWSS_

LIMITVCSH

REF

REFIREF

, V

Rising edge, 200mV typical hysteresis 4.1 4.5 V

With respect to REFIN_, REFIN_ = 0.5V to 2.5V, SKIP_ = V

Either SMPS (Note 2) 0.5 2.5 V

OSC

432kΩ (f

During transition 3.75 5.50

Startup and shutdown 0.7 1.2

VCC = 4.5V to 5.5V, I

= 0µA to 250µA 2 mV

= -50µA 10 mV

REF

[V(CSH1,CSL1) - V(CSH2,CSL2)] at I

or GND (Note 1)

= 143kΩ (f

= 71.5kΩ (f

= 99kHz nominal)

OSC

_ - V

CSL

= 300kHz nominal) -15 +15

OSC

= 600kHz nominal) to

OSC

_2535mV

= 0 2.462 2.538 V

REF

= 0 -3 +3 mV

CCI

426

4.5 5.5

-7.5 +7.5 mV

-20 +20

90 %

µA

MAX8775

Dual and Combinable Graphics Core Controller for Notebook Computers

6 _______________________________________________________________________________________

Note 1: When the inductor is in continuous conduction, the output voltage has a DC regulation level lower than the error comparator

threshold by 50% of the ripple. In discontinuous conduction, the output voltage has a DC regulation level higher than the error comparator threshold by 50% of the ripple.

Note 2: Operation below 0.5V but above the REFOK threshold is allowed, but the accuracy is not guaranteed. Note 3: The MAX8775 cannot operate over all combinations of frequency, input voltage (V

), and output voltage. For large input-tooutput differentials and high switching-frequency settings, the required on-time might be too short to maintain the regulation specifications. Under these conditions, a lower operating frequency must be selected. The minimum on-time must be greater than 150ns, regardless of the selected switching frequency. On-time and off-time specifications are measured from the 50% point to the 50% point at the DH_ pin with LX_ = GND, VBST_ = 5V, and a 250pF capacitor connected from DH_ to LX_. Actual in-circuit times may differ due to MOSFET switching speeds.

Note 4: Specifications are guaranteed by design, not production tested. Note 5: Production testing limitations due to package handling require relaxed maximum on-resistance specifications for the

thin QFN package.

Note 6: Specifications to T

= -40°C to +85°C are guaranteed by design, not production tested.

ELECTRICAL CHARACTERISTICS (continued)

(Circuit of Figure 1, VIN= 12V, SKIP_ = 0, ON_ = VCC= 5V, separate mode, TA= -40°C to +85°C, unless otherwise noted.) (Note 6)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

FAULT DETECTION

OVP_ Adjust Range V

O utp ut O ver vol tag e Tr i p Thr eshol d

Output Undervoltage Protection Trip Threshold

PGOOD_ Lower Trip Threshold

PGOOD_ Output Low Voltage I

Current-Balance Fault Comparator Thresholds

GATE DRIVERS

DH_ Gate Driver On-Resistance R

DL_ Gate Driver On-Resistance (Note 4)

INPUTS AND OUTPUTS

Logic Input-High Threshold

OVP_

Rising edge measured at CSL_, with respect to OVP_ set voltage

Falling edge measured at CSL_, with respect to error comparator threshold

Falling edge measured at CSL_ with respect to error comparator threshold, hysteresis = 1%

= 4mA 0.4 V

SINK

Lower threshold,

0.84V

V(CCI2, REF),

0.5V ≤ V

BST_ - LX_ forced to 5V (Note 4) 5 Ω

DL_, high state 5

DL_, low state 3

ON1, ON2, DTRANS, SKIP1, SKIP2, hysteresis = 225mV

≤ 2.5V

REF

Upper threshold,

1.2V

REF

0.5 2.5 V

180 220 mV

275 325 mV

-180 -120 mV

2.0 2.2

2.9 3.1

1.2 2.2 V

MAX8775

Dual and Combinable Graphics Core

Controller for Notebook Computers

_______________________________________________________________________________________

Typical Operating Characteristics

(Circuit of Figure 1, V

IN =

12V, VDD= VCC= 5V, SKIP_ = GND, T

A =

+25°C, unless otherwise noted.)

1-PHASE EFFICIENCY

vs. LOAD CURRENT (V

100

EFFICIENCY (%)

0.1 100 LOAD CURRENT (A)

OUTPUT VOLTAGE vs. LOAD CURRENT

1.505

1.503

1.501

1.499

OUTPUT VOLTAGE (V)

1.497

1.495 030

LOAD CURRENT (A)

= 1.5V)

OUT

VIN = 7V, PWM

= 12V, PWM

= 20V, PWM

= 7V, SKIP

= 12V, SKIP

= 20V, SKIP

101

VIN = 12V

= 1.5V

OUT

PWM MODE SKIP MODE

20 2510 155

MAX8775 toc01

MAX8775 toc04

vs. LOAD CURRENT (V

100

EFFICIENCY (%)

0.1 100

vs. LOAD CURRENT (V

100

EFFICIENCY (%)

0.1 100

2-PHASE EFFICIENCY

LOAD CURRENT (A)

EFFICIENCY

LOAD CURRENT (A)

= 1.5V)

OUT

VIN = 7V, PWM V

= 12V, PWM

= 20V, PWM

= 7V, SKIP

= 12V, SKIP

= 20V, SKIP

101

= 1.2V)

OUT

= 12V

= 1.2V

OUT

1-PHASE, PWM 2-PHASE, PWM 1-PHASE, SKIP 2-PHASE, SKIP

101

100

MAX8775 toc02

EFFICIENCY (%)

MAX8775 toc05

0.1

SUPPLY CURRENT (mA)

0.01

0.001

vs. LOAD CURRENT (V

EFFICIENCY

0.1 100 LOAD CURRENT (A)

NO-LOAD SUPPLY CURRENT

vs. INPUT VOLTAGE (SKIP MODE)

024

INPUT VOLTAGE (V)

OUT

= 12V

= 1.5V

OUT

1-PHASE, PWM 2-PHASE, PWM 1-PHASE, SKIP 2-PHASE, SKIP

101

16 208124

= 1.5V)

MAX8775 toc03

MAX8775 toc06

NO-LOAD SUPPLY CURRENT

vs. INPUT VOLTAGE (1-PHASE PWM MODE)

100

SUPPLY CURRENT (mA)

024

INPUT VOLTAGE (V)

16 208124

100

MAX8775 toc07

SUPPLY CURRENT (mA)

NO-LOAD SUPPLY CURRENT

vs. INPUT VOLTAGE (2-PHASE PWM MODE)

024

INPUT VOLTAGE (V)

CURRENT-SENSE OFFSET

vs. LOAD CURRENT (2-PHASE PWM MODE)

1.0

MAX8775 toc08

16 208124

0.5

-0.5

CURRENT BALANCE OFFSET (mV)

-1.0 030

LOAD CURRENT (A)

20 2510 155

MAX8775 toc09

MAX8775

Dual and Combinable Graphics Core Controller for Notebook Computers

8 _______________________________________________________________________________________

Typical Operating Characteristics (continued)

(Circuit of Figure 1, V

IN =

12V, VDD= VCC= 5V, SKIP_ = GND, T

A =

+25°C, unless otherwise noted.)

STARTUP WAVEFORMS

MAX8775 toc10

200μs/div

D: PGOOD1, 5V/div E: I

LX1

, 5A/div

A: ON1, 5V/div B: DL1, 5V/div C: V

OUT1

, 1V/div

SKIP1 = GND, R

LOAD1

= 1Ω, VIN = 12V

SHUTDOWN WAVEFORMS

MAX8775 toc11

1.5V

D: PGOOD1, 5V/div E: I

LX1

, 5A/div

A: ON1, 5V/div B: DL1, 5V/div C: V

OUT1

, 1V/div

SKIP1 = GND, R

LOAD1

= 1Ω, VIN = 12V

200μs/div

STARTUP/SHUTDOWN—

SAME SLEW RATE

D: PGOOD1, 5V/div E: PGOOD2, 5V/div

A: ON1, ON2, 5V/div B: V

OUT1

, 1V/div

C: V

OUT2

, 1V/div

SLEW1

= C

SLEW2

= 470pF

LOAD1

= R

LOAD2

= 1

400μs/div

MAX8775 toc12

STARTUP/SHUTDOWN—

SAME START TIME

MAX8775 toc13

400μs/div

D: PGOOD1, 5V/div E: PGOOD2, 5V/div

A: ON1, ON2, 5V/div B: V

OUT1

, 1V/div

C: V

OUT2

, 1V/div

SLEW1

= 470pF, C

SLEW2

= 600pF

LOAD1

= R

LOAD2

= 1

LOAD TRANSIENT (SEPARATE MODE)

MAX8775 toc14

10A

20μs/div

1.2V

12V

C: LX1, 10V/div D: I

LX1

, 10A/div

A: V

OUT1

, 100mV/div

B: DL1, 5V/div V

= 12V, V

OUT1

= 1.2V SKIP1 = GND I

OUT1

= 1A TO 11A TO 1A

LOAD TRANSIENT (COMBINED MODE)

MAX8775 toc15

10A

1.5V

12V

C: LX1, 10V/div D: LX2, 10V/div

A: V

OUT1

, 100mV/div

B: I

LX1

, 10A/div

VIN = 12V, V

OUT

= 1.5V

OUT1

= 5A TO 25A TO 5A

20μs/div

MAX8775

Dual and Combinable Graphics Core

Controller for Notebook Computers

_______________________________________________________________________________________

Typical Operating Characteristics (continued)

(Circuit of Figure 1, V

IN =

12V, VDD= VCC= 5V, SKIP_ = GND, T

A =

+25°C, unless otherwise noted.)

SWITCHING WAVEFORMS

MAX8775 toc16

12V

1.5V

1.2V

12V

D: V

OUT2

, 50mV/div

E: V

, 50mV/div

A: LX1, 10V/div B: LX2, 10V/div C: V

OUT1

, 50mV/div

VIN = 12V, V

OUT1

= 1.5V, V

OUT2

= 1.2V

OUT1

= 5A, I

OUT2

= 5A

2μs/div

REFIN TRANSITION WAVEFORMS

(DTRANS = V

)

MAX8775 toc17

12V

1.5V

1.2V

10A

C: V

OUT1

, 200mV/div

D: I

LX1

, 10A/div

A: REFIN1, 500mV/div B: LX1, 10A/div

= 12V, V

REFIN1

= 1.2V TO 1.5V TO 1.2V

OUT1

= 1A

SKIP1 = GND

100μs/div

REFIN TRANSITION WAVEFORMS

(DTRANS = GND)

MAX8775 toc18

12V

1.5V

1.2V

C: V

OUT1

, 200mV/div

D: I

LX1

, 10A/div

A: REFIN1, 500mV/div B: LX1, 10A/div

= 12V, V

REFIN1

= 1.2V TO 1.5V TO 1.2V

OUT1

= 1A

SKIP1 = GND

40μs/div

COMBINED-MODE PHASE TRANSITION

MAX8775 toc19

12V

1.2V

C: LX1, 10V/div D: LX2, 10V/div

A: V

OUT

, 50mV/div

B: ON2, 5V/div V

= 12V, V

OUT

= 1.2V

OUT

= 10A

10μs/div

COMBINED-MODE PHASE TRANSITION

MAX8775 toc20

10A

1.2V

C: I

LX2

, 10A/div

D: I

LX1

, 10A/div

A: V

OUT

, 50mV/div

B: ON2, 5V/div V

= 12V, V

OUT

= 1.2V

OUT

= 10A

10μs/div

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