Rainbow Electronics MAX1636 User Manual

General Description

The MAX1636 is a synchronous, buck, switch-mode,
power-supply controller that generates the CPU supply
voltage in battery-powered systems. It achieves ±1%
output voltage accuracy and offers the excellent load­transient response needed by upcoming generations of
dynamic-clock CPUs.

Up to 95% efficiency is achieved through synchronous
rectification and Maxim’s proprietary Idle Mode™ con­trol scheme. Efficiency is greater than 80% over a
1000:1 load-current range, extending battery life in sys­tem-suspend or standby modes. Excellent dynamic
response corrects output load transients caused by the
latest dynamic-clock CPUs within five 300kHz clock
cycles. Strong, 1A, on-board gate drivers ensure fast,
external N-channel MOSFET switching.

The MAX1636 features a logic-controlled and synchro­nizable, fixed-frequency, pulse-width-modulation (PWM)
operating mode that reduces noise and RF interference
in sensitive mobile communications and pen-entry appli­cations. Holding SKIP high forces fixed-frequency mode
for lowest noise under all load conditions.

For a low-cost version that omits the +5V VL linear­regulator block and comes in a smaller 16-pin QSOP
package, refer to the MAX1637 data sheet.

Applications

Notebook Computers

Subnotebook Computers

Desktop Computers

Bus-Termination Supplies

Features

♦ ±1% DC Accuracy (Adjustable Mode)

♦ Output Overvoltage Crowbar Protection

♦ Output Undervoltage Shutdown

♦ Adjustable Switching Frequency to 340kHz

♦ Low-Dropout Operation

♦ Idle Mode Pulse-Skipping Operation

♦ 1.10V to 5.5V Adjustable Output Voltage

♦ 2.5V/3.3V Dual-Mode Fixed-Output Settings

♦ Internal Digital Soft-Start

♦ 1.1V ±1% Reference Output

♦ 3µA (typ) Shutdown Current

♦ Open-Drain Power-Good Output (

RREESSEETT

)

♦ 20-Pin SSOP Package

MAX1636

Low-Voltage, Precision Step-Down

Controller for Portable CPU Power

________________________________________________________________ Maxim Integrated Products 1

19-1268; Rev 2; 2/98

EVALUATION KIT MANUAL

FOLLOW

S DATA SHEET

Idle Mode is a trademark of Maxim Integrated Products.

Pin Configuration

Typical Operating Circuit

Ordering Information

MAX1636

V+ SHDN

GND

V

IN

DL

PGND

LX

DH

VL

V

CC

BST

OVP

CSH

CSL

FB

RESET

TO µP

CC

SKIP

GND

SYNC

REF

PART

MAX1636EAP -40°C to +85°C

TEMP. RANGE PIN-PACKAGE

20 SSOP

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.

TOP VIEW

1

CSH

2

CSL

3

RESET

4

MAX1636

5

OVP

6

CC

7

REF

8

9

GND

10

SSOP

20

SKIP

19

LX

18

DH

17

BSTSHDN

16

PGND

15

DL

14

VL

13

V+SYNC

12

V

CC

11

FBGND

mV

MAX1636

Low-Voltage, Precision Step-Down
Controller for Portable CPU Power

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(Circuit of Figure 1, V+ = 15V, SYNC = VL = VCC, IVL= 0mA, I

REF

= 0mA, TA= 0°C to +85°C, unless otherwise noted. Typical values

are at T

A

= +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.

V+ to GND ...............................................................-0.3V to 36V

GND to PGND........................................................................±2V

SHDN to GND. ......................................................... -0.3V to 36V

LX, BST to GND. ...................................................... -0.3V to 36V

DH, BST to LX .............................................................-0.3V to 6V

VL, V

CC

, CSL, CSH, FB, SKIP to GND ...................... -0.3V to 6V

DL to GND.. ..................................................-0.3V to (VL + 0.3V)

REF, RESET, SYNC, CC, OVP to GND. ..... -0.3V to (V

CC

+ 0.3V)

VL Output Current... ............................................................50mA

VL Short Circuit to GND..............................................Momentary

REF Output Current ............................................................20mA

REF Short Circuit to GND ....... ......................................Indefinite

Continuous Power Dissipation (T

A

= +70°C)

SSOP (derate 8.00mW/°C above +70°C) .....................640mW

Operating Temperature Range

MAX1636EAP. ..................................................-40°C to +85°C

Storage Temperature Range .............................-65°C to +160°C

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

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

Gate-driver supply rail

CSH - CSL

Input source for VL regulator

SHDN to full current limit, five levels

FB forced to REF

Positive direction

SHDN = GND, OVP = GND

VCC= 3.3V, output not switching

VCC= 3.3V, VL = 5V

VCC= VL = 5V

Internal chip supply rail

FB tied to V

OUT

, 0mV < (CSH - CSL) < 80mV, 4.5V

< V+ < 30V (includes line and load regulation)

FB tied to VCC, 0mV < (CSH - CSL) < 80mV, 4.5V
< V+ < 30V (includes line and load regulation)

VCC= 5V, output not switching

FB tied to GND, 0mV < (CSH - CSL) < 80mV, 4.5V
< V+ < 30V (includes line and load regulation)

Negative direction

CONDITIONS

mV20 30 40Idle Mode Switchover Threshold

clks512Soft-Start Ramp Time

nA-50 50FB Input Current

µA310Shutdown Supply Current (V+)

1.5

Power Consumption

2.0

-145 -100 -55

V4.2 5.5Input Voltage Range, VL

V4.5 30Input Voltage Range, V+

mV

80 100 120

Current-Limit Threshold

V

REF

3.6

V

V

REF

5.5

Output Adjustment Range

V3.15 5.5Input Voltage Range, V

CC

V1.090 1.100 1.110Output Voltage, Adj Mode

V2.486 2.55 2.614 Output Voltage, Fixed 2.5V Mode

V3.282 3.366 3.450Output Voltage, Fixed 3.3V Mode

UNITSMIN TYP MAXPARAMETER

mW

SMPS CONTROLLER

MAX1636

Low-Voltage, Precision Step-Down

Controller for Portable CPU Power

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(Circuit of Figure 1, V+ = 15V, SYNC = VL = VCC, IVL= 0mA, I

REF

= 0mA, TA= 0°C to +85°C, unless otherwise noted. Typical values

are at T

A

= +25°C.)

%

FB to DL delay, 22mV overdrive, C

GATE

= 2000pF

SHDN = GND, OVP = V

CC

FB, with respect to regulation point

VCC= 5V, I(VL) = 0, V+ = 4.5V
(includes PNP base current)

VCC= 5V, I(VL) = 0

Guaranteed by design

SYNC = V

CC

SYNC = GND

SYNC = V

CC

I(VL) = 0 to 25mA, 5V < V+ < 30V

I(VL) = 0 to 25mA, 6V < V+ < 30V

Rising edge, hysteresis = 25mV

SYNC = GND

REF load = 0 to 50µA

SYNC = GND

°C

150

µs

1.25

%

4 7 10

kHz

240 340

SYNC Input Frequency Range

ns

200

SYNC Input Rise/Fall Time

ns

200

SYNC Input Pulse Width Low

200

Maximum Duty Factor, Dropout Mode

98 99

93 96

µA

60

Standby Supply Current (V+)

µA

500

Regulator Supply Current (V+)

60

91 94

170 200 230

270 300 330

kHz

V

4.5 5.0 5.3

4.7 5.0 5.3

VL Output Voltage

V

3.15

VL/ VCCSwitchover Threshold

mV

10

REF Load Regulation

Hysteresis = 10°C

Rising edge, hysteresis = 25mV V

3.45 3.60 3.75

VL Undervoltage Lockout Threshold

No REF load V

1.090 1.100 1.110

REF Output Voltage

VCC= 3.3V to 5.5V mV

3

REF Line Regulation

Oscillator Frequency

%

nsSYNC Input Pulse Width High

Maximum Duty Factor

Overvoltage Trip Threshold

Thermal Shutdown Threshold

Overvoltage Fault Propagation Delay

%

Pin at GND or VCC; SKIP, OVP, SYNC

SHDN, SKIP, OVP, SYNC

SHDN, SKIP, OVP, SYNC

Falling edge (hysteresis = 1%)

From shutdown or power-on-reset state

% of nominal output

V

0.4

RESET Output Voltage Low

µA

-1 1

V

0.8

V

2.4

Logic Input Voltage High

clks

Catastrophic Output Undervoltage
Lockout Delay

Logic Input Voltage Low

Logic Input Bias Current

clks

32768

RESET Delay Time

%

-6 -3

RESET Trip Threshold

6144

Catastrophic Output Undervoltage
Lockout Threshold

60 70 80

I

SINK

= 4mA

+5.5V stress voltage applied µA

1

RESET Output Leakage Current

CONDITIONS UNITSMIN TYP MAXPARAMETER

SHDN = GND or V+

µA

-3 3

SHDN Input Bias Current

INTERNAL VL REGULATOR AND REFERENCE

OSCILLATOR

OVERVOLTAGE PROTECTION

INPUTS AND OUTPUTS

MAX1636

Low-Voltage, Precision Step-Down
Controller for Portable CPU Power

4 _______________________________________________________________________________________

Gate-driver supply rail

Input source for VL regulator

VCC= 3.3V, VL = 5V

VCC= VL = 5V

Internal chip supply rail

FB tied to V

OUT

, 0mV < (CSH - CSL) < 80mV, 4.5V

< V+ < 30V (includes line and load regulation)

FB tied to VCC, 0mV < (CSH - CSL) < 80mV, 4.5V
< V+ < 30V (includes line and load regulation)

FB tied to GND, 0mV < (CSH - CSL) < 80mV, 4.5V
< V+ < 30V (includes line and load regulation)

CONDITIONS

V4.2 5.5Input Voltage Range, VL

V4.5 30Input Voltage Range, V+

V

REF

3.6

V

V

REF

5.5

Output Adjustment Range

V3.15 5.5Input Voltage Range, V

CC

V1.086 1.114Output Voltage, Adj Mode

V2.432 2.635 Output Voltage, Fixed 2.5V Mode

V3.195 3.497Output Voltage, Fixed 3.3V Mode

UNITSMIN TYP MAXPARAMETER

High or low, DH or DL

DH or DL forced to 2V

CSH = CSL = 5V, V+ = VL = VCC=
GND, either CSH or CSL input

CONDITIONS

Ω7Gate-Driver On-Resistance

A1Gate-Driver Sink/Source Current

µA10

Current-Sense Input
Leakage Current

UNITSMIN TYP MAXPARAMETER

ELECTRICAL CHARACTERISTICS (continued)

(Circuit of Figure 1, V+ = 15V, SYNC = VL = VCC, IVL= 0mA, I

REF

= 0mA, TA= 0°C to +85°C, unless otherwise noted. Typical values

are at T

A

= +25°C.)

ELECTRICAL CHARACTERISTICS

(Circuit of Figure 1, V+ = 15V, SYNC = VL = VCC, IVL= 0mA, I

REF

= 0mA, TA=-40°C to +85°C, unless otherwise noted.) (Note 1)

VCC= 5V, I(VL) = 0

µA

60

Regulator Supply Current (V+)

VCC= 5V, I(VL) = 0, V+ = 4.5V
(includes PNP base current)

SHDN = GND, OVP = V

CC

µA60Standby Supply Current (V+)

I(VL) = 0 to 25mA, 6V < V+ < 30V

V

4.7 5.3

I(VL) = 0 to 25mA, 5V < V+ < 30V

VL Output Voltage

Rising edge, hysteresis = 25mV V3.45 3.91

4.5 5.3

VL Undervoltage Lockout
Threshold

500

VCC= 5V, output not switching

Positive direction

2.0

mV70 130Current-Limit Threshold

VCC= 3.3V, output not switching 1.5

Power Consumption mW

SMPS CONTROLLER

INTERNAL VL REGULATOR AND REFERENCE

MAX1636

Low-Voltage, Precision Step-Down

Controller for Portable CPU Power

_______________________________________________________________________________________ 5

ELECTRICAL CHARACTERISTICS (continued)

(Circuit of Figure 1, V+ = 15V, SYNC = VL = VCC, IVL= 0mA, I

REF

= 0mA, TA= -40°C to +85°C, unless otherwise noted.) (Note 1)

FB, with respect to regulation point

Guaranteed by design

SYNC = GND

SYNC = V

CC

%

3.5 10

Oscillator Frequency

nsSYNC Input Pulse Width High

Overvoltage Trip Threshold

kHz

240 340

SYNC Input Frequency Range

%

ns

200

SYNC Input Rise/Fall Time

ns

200

SYNC Input Pulse Width Low

SHDN, SKIP, OVP, SYNC

SHDN, SKIP, OVP, SYNC

200

Falling edge (hysteresis = 1%)

% of nominal output

V

0.4

RESET Output Voltage Low

V

0.8

V

170 230

2.4

270 330

Logic Input Voltage High

kHz

Logic Input Voltage Low

%

-7 -1.5

RESET Trip Threshold

Catastrophic Output Undervoltage
Lockout Threshold

60 80

I

SINK

= 4mA

High or low, DH or DL Ω

7

Gate-Driver On-Resistance

CONDITIONS UNITSMIN TYP MAXPARAMETER

OSCILLATOR

OVERVOLTAGE PROTECTION

INPUTS AND OUTPUTS

__________________________________________Typical Operating Characteristics

(Circuit of Figure 1, VIN= 7V, TA= +25°C, unless otherwise noted.)

100

50

1m 100m 110m 10

EFFICIENCY vs. LOAD CURRENT

(3.3V/3A CIRCUIT)

60

MAX1636 TOC01

LOAD CURRENT (A)

EFFICIENCY (%)

70

80

90

VIN = 22V

VIN = 30V

VIN = 7V

VIN = 15V

100

50

1m 100m 110m 10

EFFICIENCY vs. LOAD CURRENT

(5V/3A CIRCUIT)

60

MAX1636 TOC02

LOAD CURRENT (A)

EFFICIENCY (%)

70

80

90

VIN = 22V

VIN = 7V

VIN = 15V

VIN = 30V

100

50

1m 100m 110m 10

EFFICIENCY vs. LOAD CURRENT

(1.8V/1A CIRCUIT)

60

MAX1636 TOC03

LOAD CURRENT (A)

EFFICIENCY (%)

70

80

90

VIN = 15V

VIN = 7V

VIN = 22V

Note 1: Specifications to -40°C are guaranteed by design and not production tested.

50

100

75

150

125

225

200

175

250

150 250200 300 350 400 450 500

MAX1636 TOC11

F

OSC

(kHz)

RESET TIME DELAY (ms)

RESET TIME DELAY

vs. OSC FREQUENCY

V

OUT

50mV/div

LOAD
CURRENT

0A

2A

4A

LOAD-TRANSIENT RESPONSE

(3.3V/3A, PWM MODE)

MAX1636 TOC12

100µs/div)

50

150

100

250

200

350

300

400

0 1.0 1.50.5 2.0 2.5 3.0 3.5

DROPOUT VOLTAGE

vs. LOAD CURRENT

MAX1636 TOC10

LOAD CURRENT (A)

V

IN

- V

OUT

(mV)

V

OUT

FORCED TO 4.95V

MAX1636

Low-Voltage, Precision Step-Down
Controller for Portable CPU Power

6 _______________________________________________________________________________________

_____________________________Typical Operating Characteristics (continued)

(Circuit of Figure 1, VIN= 7V, TA = +25°C, unless otherwise noted.)

100

50

1m 100m 110m 10

EFFICIENCY vs. LOAD CURRENT

(1.8V/4A CIRCUIT)

60

MAX1636 TOC04

LOAD CURRENT (A)

EFFICIENCY (%)

70

80

90

VIN = 7V

VIN = 22V

VIN = 15V

100

50

1m 100m 110m 10

EFFICIENCY vs. LOAD CURRENT

(1.8V/7A CIRCUIT)

60

MAX1636 TOC05

LOAD CURRENT (A)

EFFICIENCY (%)

70

80

90

VIN = 15V

VIN = 7V

VIN = 22V

1000

0.01
015202510530

QUIESCENT SUPPLY CURRENT

vs. INPUT VOLTAGE

0.10

MAX1636 TOC06

INPUT VOLTAGE (V)

QUIESCENT SUPPLY CURRENT (mA)

1

10

100

V

OUT

= 3.3V

0

10

5

15

30

35

25

20

40

0 101520255 3035404550

VL LOAD-REGULATION ERROR

vs. VL LOAD CURRENT

MAX1636 TOC08

VL LOAD CURRENT (mA)

LOAD REGULATION ∆V (mV)

0

0.3

0.2

0.1

0.4

0.5

0.6

0403010 20 50 60 70 80 90 100

REF LOAD-REGULATION ERROR

vs. REF LOAD CURRENT

MAX1636 TOC09

REF LOAD CURRENT (µA)

LOAD REGULATION ∆V (mV)

LOAD REGULATION

PWM MODE

= 5V

V

OUT

vs. LOAD CURRENT

MAX1636 TOC07

LOAD CURRENT (A)

5

4

3

(mV)

2

OUT

1

0

-1

-2

LOAD REGULATION ∆ V

-3

-4

-5
1m 100m 110m 10

MAX1636

Low-Voltage, Precision Step-Down

Controller for Portable CPU Power

_______________________________________________________________________________________ 7

_____________________________Typical Operating Characteristics (continued)

(Circuit of Figure 1, VIN= 7V, TA = +25°C, unless otherwise noted.)

V

OUT

50mV/div

5A LOAD CURRENT

0A

10A

LOAD-TRANSIENT RESPONSE

(1.8V, PWM MODE)

MAX1636 TOC13

100µs/div

V

OUT

20mV/div

V

LX

INDUCTOR
CURRENT

1A

0V

5V

0A

SWITCHING WAVEFORMS

(PWM MODE)

MAX1636 TOC14

1µs/div

V

OUT

50mV/div

V

LX

INDUCTOR
CURRENT

1A

0V

5V

0A

SWITCHING WAVEFORMS

(PFM MODE)

MAX1636 TOC15

20µs/div

V

OUT

= 1.8V

V

OUT

1V/div

V

SHDN

5V/div

STANDBY AND STARTUP RESPONSE

(V

OUT

= 1.8V, NO LOAD)

MAX1636 TOC17

1ms/div

V

OUT

20mV/div

V

LX

INDUCTOR
CURRENT

4A

0

5V

2A

0A

SWITCHING WAVEFORMS

(DROPOUT OPERATION)

MAX1636 TOC16

5µs/div

V

OUT

= 5V

V

OUT

100mV/div

V

DL

INDUCTOR
CURRENT

-5A

0

0

5V

-10A

OVERVOLTAGE-PROTECTION WAVEFORMS

(V

IN

SHORTED TO V

OUT

THROUGH a 0.5Ω RESISTOR)

MAX1636 TOC18

10µs/div