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General Description

The MAX1714 pulse-width modulation (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 or chip-set/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 MAX1714 achieves high efficiency at a reduced

cost by eliminating the current-sense resistor found in

traditional current-mode PWMs. Efficiency is further

enhanced by an ability to drive very large synchronous-

rectifier MOSFETs.

Single-stage buck conversion allows these devices 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 mini-

mum possible physical size.

The MAX1714 is intended for CPU core, chipset,

DRAM, or other low-voltage supplies as low as 1V. The

MAX1714A is available in a 20-pin QSOP package and

includes overvoltage protection. The MAX1714B is

available in a 16-pin QSOP package with no overvolt-

age protection. For applications requiring VID compli-

ance or DAC control of output voltage, refer to the

MAX1710/MAX1711 data sheet. For a dual output ver-

sion, refer to the MAX1715

†

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

♦ 2.5V/3.3V Fixed or 1V to 5.5V Adjustable Output

Range

♦ 2V to 28V Battery Input Range

♦ 200/300/450/600kHz Switching Frequency

♦ Overvoltage Protection (MAX1714A)

♦ Undervoltage Protection

♦ 1.7ms Digital Soft-Start

♦ Drives Large Synchronous-Rectifier FETs

♦ 2V ±1% Reference Output

♦ Power-Good Indicator

MAX1714

High-Speed Step-Down Controller

for Notebook Computers

________________________________________________________________ Maxim Integrated Products 1

19-1536; Rev 2; 8/05

Pin Configurations appear at end of data sheet.

Quick-PWM is a trademark of Maxim Integrated Products.

†

Future product—contact factory for availability.

-40°C to +85°C

PART

MAX1714AEEP

TEMP RANGE PIN-PACKAGE

20 QSOP

Ordering Information

+5V INPUT

BATTERY

4.5V TO 28V

OUTPUT

1.25V TO 2V

SHDN

ILIM

V+

BST

PGND

(GND)

OUT

SKIP

MAX1714

REF

PGOOD

AGND

(GND)

( ) ARE FOR THE MAX1714B ONLY.

Minimal Operating Circuit

MAX1714AEEP+ -40°C to +85°C 20 QSOP

+Denotes lead-free package.

MAX1714BEEE -40°C to +85°C 16 QSOP

MAX1714BEEE+ -40°C to +85°C 16 QSOP

EVALUATION KIT

AVAILABLE

Summary of content (24 pages)

PAGE 1
9-1536; Rev 2; 8/05 KIT ATION EVALU E L B AVAILA High-Speed Step-Down Controller for Notebook Computers The MAX1714 pulse-width modulation (PWM) controller provides the high efficiency, excellent transient response, and high DC output accuracy needed for stepping down high-voltage batteries to generate lowvoltage CPU core or chip-set/RAM supplies in notebook computers.
PAGE 2
MAX1714 High-Speed Step-Down Controller for Notebook Computers ABSOLUTE MAXIMUM RATINGS V+ to AGND (Note 1)..............................................-0.3V to +30V LX to BST..................................................................-6V to +0.3V VDD, VCC to AGND (Note 1) .....................................-0.3V to +6V REF Short Circuit to AGND.........................................Continuous PGND to AGND (Note 1) ................................................... ±0.
PAGE 3
High-Speed Step-Down Controller for Notebook Computers (Circuit of Figure 1, 4A components from Table 1, V+ = +15V, VCC = VDD = +5V, SKIP = AGND, TA = 0°C to +85°C, unless otherwise noted.) (Note 1) CONDITIONS MIN TYP MAX UNITS Overvoltage Trip Threshold PARAMETER With respect to error comparator threshold (MAX1714A only) 10.5 12.5 14.
PAGE 4
MAX1714 High-Speed Step-Down Controller for Notebook Computers ELECTRICAL CHARACTERISTICS (continued) (Circuit of Figure 1, 4A components from Table 1, V+ = +15V, VCC = VDD = +5V, SKIP = AGND, TA = 0°C to +85°C, unless otherwise noted.) (Note 1) PARAMETER CONDITIONS TON VCC Level MIN TYP MAX VCC - 0.4 UNITS V TON Float Voltage 3.15 3.85 V TON Reference Level 1.65 2.35 V 0.
PAGE 5
High-Speed Step-Down Controller for Notebook Computers (Circuit of Figure 1, 4A components from Table 1, V+ = +15V, VCC = VDD = +5V, SKIP = AGND, TA = -40°C to +85°C, unless otherwise noted.) (Notes 1, 5) PARAMETER CONDITIONS MIN PGOOD Trip Threshold Measured at FB with respect to error comparator threshold, falling edge PGOOD Output Low Voltage ISINK = 1mA PGOOD Leakage Current High state, forced to 5.5V TYP -8 MAX UNIT -4 % 0.
PAGE 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.) 300 330 325 VIN = 7V SKIP MODE 200 150 VIN = 15V SKIP MODE FREQUENCY (kHz) FREQUENCY (kHz) 250 300 320 315 310 290 IOUT = 1A 305 50 280 0 0.01 0.1 1 5 10 15 20 25 30 -40 20 40 60 80 TEMPERATURE (°C) IOUT AT CURRENT LIMIT vs. TEMPERATURE (4A COMPONENTS, VOUT = 2.
PAGE 7
High-Speed Step-Down Controller for Notebook Computers (Circuit of Figure 1, components from Table 1, VIN = +15V, SKIP = AGND, TON = unconnected, TA = +25°C, unless otherwise noted.) A MAX1714B-15 MAX1714B-14 MAX1714B-13 LOAD-TRANSIENT RESPONSE (1.5A COMPONENTS, VIN = 5V, VOUT = 2.5V, 600kHz) LOAD-TRANSIENT RESPONSE (8A COMPONENTS, VOUT = 1.6V, 300kHz) LOAD-TRANSIENT RESPONSE (4A COMPONENTS, VOUT = 2.
PAGE 8
High-Speed Step-Down Controller for Notebook Computers MAX1714 Pin Description PIN PIN NAME 8 FUNCTION MAX1714A MAX1714B 1 1 DH High-Side Gate Driver Output. Swings from LX to BST. 2, 9, 11 – N.C. No Connection. These pins are not connected to any internal circuitry. Connect N.C. pins to the ground plane to enhance thermal conductivity. 3 2 SHDN Shutdown Control Input. Drive SHDN to AGND to force the MAX1714 into shutdown. Drive or connect to VCC for normal operation.
PAGE 9
High-Speed Step-Down Controller for Notebook Computers Detailed Description The standard application circuit (Figure 1) generates a low-voltage rail for general-purpose use in a notebook computer (I/O supply, fixed CPU core supply, DRAM supply). This DC-DC converter steps down a battery or AC adapter voltage to voltages from 1.0V to 5.5V with high efficiency and accuracy. See Table 1 for a list of component selections for common applications. Table 2 lists component manufacturers.
PAGE 10
MAX1714 High-Speed Step-Down Controller for Notebook Computers Table 1. Component Selection for Standard Applications COMPONENT 2.5V AT 4A 1.6V AT 8A 2.5V AT 1.5A Input Range 7V to 20V 7V to 20V 4.5V to 5.
PAGE 11
High-Speed Step-Down Controller for Notebook Computers MAX1714 IN 2V TO 28V V+ ILIM TOFF TON FROM OUT ON-TIME COMPUTE 9R BST R TON S Q TRIG +5V MAX1714 1-SHOT TRIG Q Q R DH CURRENT LIMIT 1-SHOT Σ LX ERROR AMP SKIP ZERO CROSSING VDD REF SHDN OUTPUT +5V DL S Q (MAX1714B ONLY) R PGND (GND) OUT MAX1714A ONLY x2 REF -6% REF +12% +5V REF -30% FEEDBACK MUX (SEE FIGURE 9) PGOOD S1 S2 VCC CHIP SUPPLY 2V REF REF TIMER Q (GND) AGND OVP/UVLO LATCH FB NOTE: IN THE MAX1714B, A
PAGE 12
MAX1714 High-Speed Step-Down Controller for Notebook Computers where K is set by the TON pin-strap connection and 0.075V is an approximation to accommodate for the expected drop across the low-side MOSFET switch. One-shot timing error increases for the shorter on-time settings due to fixed propagation delays; it is approximately ±12.5% at 600kHz and 450kHz, and ±10% at the two slower settings. This translates to reduced switchingfrequency accuracy at higher frequencies (Table 5).
PAGE 13
High-Speed Step-Down Controller for Notebook Computers TIME ILOAD INDUCTOR CURRENT INDUCTOR CURRENT -IPEAK ILOAD = IPEAK/2 0 ON-TIME MAX1714 -IPEAK ∆i VBATT -VOUT = ∆t L ILIMIT 0 TIME Figure 3. Pulse-Skipping/Discontinuous Crossover Point Figure 4. ‘‘Valley’’ Current-Limit Threshold Point multiple-output applications that use a flyback transformer or coupled inductor.
PAGE 14
MAX1714 High-Speed Step-Down Controller for Notebook Computers +5V BST VIN 5Ω DH LX MAX1714 Figure 5. Reducing the Switching-Node Rise Time POR, UVLO, and Soft-Start Power-on reset (POR) occurs when VCC rises above approximately 2V, resetting the fault latch and soft-start counter, and preparing the PWM for operation. VCC undervoltage lockout (UVLO) circuitry inhibits switching and forces the DL gate driver high (to enforce output overvoltage protection) until V CC rises above 4.
PAGE 15
High-Speed Step-Down Controller for Notebook Computers SHDN SKIP DL MODE 0 X High Shutdown 1 1 1 1 Below Switching AGND COMMENTS Low-power shutdown state. DL is forced to VDD, enforcing OVP. ICC < 1µA typ. Test mode with OVP, UVP, and thermal faults disabled and latches cleared. Otherwise normal operation, with automatic PWM/PFM switchover for pulse skipping at light loads (Figure 6). No Fault Switching Run (PWM), Low Noise Low-noise operation with no automatic switchover.
PAGE 16
MAX1714 High-Speed Step-Down Controller for Notebook Computers Inductor Selection The switching frequency and inductor operating point determine the inductor value as follows: VOUT (VIN - VOUT ) L = VIN ⋅ f ⋅ LIR ⋅ I LOAD(MAX) Example: ILOAD(MAX) = 8A, VIN = 7V, VOUT = 1.5V, f = 300kHz, 33% ripple current or LIR = 0.33. 1.5V (7V - 1.5V) = 1.49µH L= 7V ⋅ 300kHz ⋅ 0.33 ⋅ 8A Find a low-loss inductor having the lowest possible DC resistance that fits in the allotted dimensions.
PAGE 17
High-Speed Step-Down Controller for Notebook Computers Output Capacitor Selection The output filter capacitor must have low enough effective series resistance (ESR) to meet output ripple and loadtransient requirements, yet have high enough ESR to satisfy stability requirements. Also, the capacitance value must be high enough to absorb the inductor energy going from a full-load to no-load condition without tripping the overvoltage protection circuit.
PAGE 18
MAX1714 High-Speed Step-Down Controller for Notebook Computers For optimal circuit reliability, choose a capacitor that has less than 10°C temperature rise at the peak ripple current. Power MOSFET Selection Most of the following MOSFET guidelines focus on the challenge of obtaining high load-current capability (>5A) when using high-voltage (>20V) AC adapters. Low-current applications usually require less attention.
PAGE 19
High-Speed Step-Down Controller for Notebook Computers MAX1714 +5V VIN = 7V TO 24V* 1µF 20Ω V+ C1 1µF VDD ILIM VCC 5Ω BST ON/OFF SHDN Q1 DH 0.5µH 0.1µF MAX1714 R1 2.5V AT 7A LX SKIP FB 0.22µF C2 Q2 DL PGND (GND) CPU R2 REF AGND (GND) 1k OUT TON C1 = 2 x 10µF/25V TAIYO YUDEN (1812) (TMK432BJ106AM) C2 = 6 x 47µF/6.3V TAIYO YUDEN (1812) (JMK432BJ476MN) R1 + R2 = 5mΩ MINIMUM OF PCB TRACE RESISTANCE (TOTAL) * FOR HIGHER MINIMUM INPUT VOLTAGE, * LESS OUTPUT CAPACITANCE IS ACCEPTABLE.
PAGE 20
MAX1714 High-Speed Step-Down Controller for Notebook Computers capacitors close to the CPU. Resistance values higher than 5mΩ just improve the stability (which can be observed by examining the load-transient response characteristic as shown in the Typical Operating Characteristics). Avoid adding excess PC board trace resistance, as there’s an efficiency penalty; 5mΩ is sufficient for a 7A circuit. RESR ≥ 1 2FCOUT VSOAR determines the minimum output capacitance requirement.
PAGE 21
High-Speed Step-Down Controller for Notebook Computers DH VOUT MAX1714 DL PGND (GND) OUT R1 FB R2 AGND (GND) ( ) ARE FOR THE MAX1714B ONLY. Figure 9. Setting VOUT with a Resistor-Divider where a single milliohm of excess trace resistance causes a measurable efficiency penalty. • LX and PGND connections to Q2 for current limiting must be made using Kelvin sense connections to guarantee the current-limit accuracy.
PAGE 22
MAX1714 High-Speed Step-Down Controller for Notebook Computers VIN 4.5V TO 5.5V 1µF 20Ω 1µF ILIM VCC C1 4 x 10µF/25V V+ VDD BST SHDN ON/OFF DH IRF7805 0.1µF MAX1714 VOUT 2.5V AT 7A L1 0.5µH C2 3 x 470µF KEMET T510 LX 0.22µF REF DL IRF7805 PGND (GND) FB VCC OUT 100k PGOOD TON AGND (GND) ( ) = ARE FOR THE MAX1714B ONLY. NOTE: IN THE MAX1714B, AGND AND PGND ARE INTERNALLY CONNECTED TO THE GND PIN. SKIP Figure 10.
PAGE 23
High-Speed Step-Down Controller for Notebook Computers MAX1714 VBATT GND IN ALL ANALOG GROUNDS CONNECT TO AGND ONLY VIA TO PGND NEAR Q2 SOURCE MAX1714 VCC REF ILIM AGND CIN ;; GND OUT Q1 D1 VDD Q2 COUT VOUT VIA TO SOURCE OF Q2 CONNECT AGND TO PGND BENEATH IC, 1 POINT ONLY. SPLIT ANALOG GND PLANE AS SHOWN. L1 VIA TO OUT NEAR COUT+ VIA TO LX NOTES: "STAR" GROUND IS USED. D1 IS DIRECTLY ACROSS Q2. INDUCTOR DISCHARGE PATH HAS LOW DC RESISTANCE. Figure 11.
PAGE 24
Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.) QSOP.EPS MAX1714 High-Speed Step-Down Controller for Notebook Computers Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied.