Rainbow Electronics MAX15010 User Manual

Page 1

General Description

The MAX15008 features a 300mA LDO regulator, a voltage tracker, and an overvoltage protection (OVP) controller to protect downstream circuits from high-voltage load dump. The MAX15010 includes only the 300mA LDO voltage regulator and voltage tracker. Both devices operate over a wide 5V to 40V supply voltage range and are able to withstand load-dump transients up to 45V. The MAX15008/MAX15010 feature short-circuit and thermalshutdown protection. These devices offer highly integrated power-management solutions for automotive applications such as instrument clusters, climate control, and a variety of automotive power-supply circuits.

The 300mA LDO regulator consumes less than 67µA quiescent current at light loads and is well suited to power always-on circuits during “key off” conditions. The LDO features independent enable and hold inputs as well as a microprocessor (µP) reset output with an adjustable reset timeout period.

The voltage tracker accurately (±3mV) tracks a voltage applied to its input from either the LDO output or an external source. It can supply up to 50mA of current to a remote sensor, allowing for precise ratiometric tracking in automotive applications. A separate enable input turns the tracker on or off, reducing supply current when the tracker is unused. The voltage tracker also features protection against battery reversal, an output short circuit to the battery, or an output-voltage excursion below ground potential to as much as -5V.

The MAX15008 OVP controller operates with an external enhancement mode n-channel MOSFET. While the monitored voltage remains below the adjustable threshold, the MOSFET stays on. When the monitored voltage exceeds the OVP threshold, the OVP controller quickly turns off the external MOSFET. The OVP controller is configurable as a load-disconnect switch or a voltage limiter.

The MAX15008/MAX15010 are available in a thermally enhanced, 32-pin (5mm x 5mm) TQFN package and are fully specified over the -40°C to +125°C automotive operating temperature range.

Applications

Instrument Clusters

Climate Control

AM/FM Radio Power Supply

Multimedia Power Supply

Telematics Power Supply

Features

o 300mA LDO Regulator, Voltage Tracker, and OVP

Controller (MAX15008)

o 300mA LDO Regulator and Voltage Tracker

(MAX15010)

o 50mA Voltage Tracker with ±3mV Tracking Accuracy

o 5V to 40V Wide Operating Supply Voltage Range

o 45V Load Dump Protection

o 67µA Quiescent Current LDO Regulator

o OVP Controller Disconnects or Limits Output from

Battery Overvoltage Conditions (MAX15008)

o LDO Regulator with Enable, Hold, and Reset

Features

MAX15008/MAX15010

Automotive 300mA LDO Voltage Regulators

with Tracker Output and Overvoltage Protector

________________________________________________________________

Maxim Integrated Products

Pin Configurations

19-0996; Rev 1; 2/08

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

Typical Operating Circuits appear at end of data sheet.

Pin Configurations continued at end of data sheet.

Ordering Information

Denotes a lead-free package.

EP = Exposed pad.

PART LDO

TRACKER

OVP

CONTROLLER

MAX15008 √√ √ MAX15010 √√ —

Selector Guide

EVALUATION KIT

AVAILABLE

PART

TEMP RANGE

PINPACKAGE

PKG

CODE

MAX15008ATJ+

T3255-4

MAX15010ATJ+

T3255-4

-40°C to +125°C 32 TQFN-EP*

TOP VIEW

N.C.

OUT_LDO

MAX15008

4567

ADJ

SGND

OUT_TRK

TQFN

(5mm x 5mm)

*EP

PGND

EN_PROT

EN_TRK

N.C.

RESET

EN_LDO

FB_LDO

REF

SOURCE

GATE

N.C.

FB_PROT

HOLD

N.C.

FB_TRK

TRACK

N.C.

*EP = EXPOSED PAD

N.C.

2324 22 20 19 18

N.C.

Page 2

MAX15008/MAX15010

Automotive 300mA LDO Voltage Regulators with Tracker Output and Overvoltage Protector

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VIN= V

TRACK

= +14V, V

SGND

= V

PGND

= 0V, C

GATE

= 6000pF, CIN= 10µF (ESR ≤ 1.5Ω), C

OUT_LDO

= 22µF (ceramic), C

TRACK

3.3µF (ceramic) (ESR ≤ 1.5Ω), C

OUT_TRK

= 10µF (ESR ≤ 1.5Ω), C

REF

= 1000pF, V

OUT_LDO

= 5V, TA= TJ= -40°C to +125°C, unless

otherwise noted. Typical values are at T

= +25°C.) (Note 1)

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.

(All pins referenced to SGND, unless otherwise noted.)

IN, GATE.................................................................-0.3V to +45V

TRACK.....................................................................-20V to +45V

EN_LDO, EN_PROT, EN_TRK .....................-0.3V to (V

+ 0.3V)

SOURCE ......................................................-0.3V to (V

+ 0.3V)

TRACK to OUT_TRK................................................-40V to +40V

OUT_TRK, FB_TRK, ADJ...........................................-5V to +45V

OUT_LDO, FB_LDO, FB_PROT, RESET.................-0.3V to +12V

GATE to SOURCE ..................................................-0.3V to +12V

HOLD................................................-0.3V to (V

OUT_LDO

+ 0.3V)

REF to SGND............................................................-0.3V to +6V

CT to SGND............................................................-0.3V to +12V

SGND to PGND .....................................................-0.3V to +0.3V

IN, OUT_LDO Current .......................................................700mA

TRACK, OUT_TRK Current ...............................................350mA

Current Sink/Source (all remaining pins) ............................50mA

Continuous Power Dissipation (T

= +70°C)

32-Pin TQFN (derate 34.5mW/°C above +70°C).............2.7W*

Thermal Resistance

..............................................................................29.0°C/W

................................................................................1.7°C/W

Operating Temperature Range .........................-40°C to +125°C

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

Storage Temperature Range .............................-60°C to +150°C

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

As per JEDEC51 Standard, Multilayer Board (PCB).

Supply Voltage Range V

Supply Current I

Shutdown Supply Current I

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

SHDN

MAX15008

MAX15010

E N _LD O = E N _P ROT = EN_TRK = 0V, measured from SGND

EN_LDO = IN, EN_TRK = EN_PROT = 0V, I = 0µA, LDO on, tracker off, protector off, measured from SGND

EN_LDO = EN_TRK = IN, EN_PROT = 0V, LDO on, I

OUT_LDO

on, I protector off, V V

OUT_TRK

measured from SGND

EN_LDO = EN_TRK = EN_PROT = IN, LDO on, I

OUT_LDO

on, I protector on, V V

OUT_TRK; VADJ

measured from SGND

EN_LDO = EN_TRK = IN, LDO on, I 100µA, tracker on, I

OUT_TRK

measured from SGND

TA = -40°C to +85°C 16 30

= 100µA, tracker

OUT_TRK

, V

= 100µA, tracker

OUT_TRK

OUT_LDO

= 0µA,

= -40°C to +125°C 40

OUT_LDO

= 0µA,

FB_TRK

= V

ADJ

= 0µA,

FB_TRK

= V

REF,

540V

67 85

120 180

190 280

115 160

µA

Page 3

MAX15008/MAX15010

Automotive 300mA LDO Voltage Regulators

with Tracker Output and Overvoltage Protector

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(VIN= V

TRACK

= +14V, V

SGND

= V

PGND

= 0V, C

GATE

= 6000pF, CIN= 10µF (ESR ≤ 1.5Ω), C

OUT_LDO

= 22µF (ceramic), C

TRACK

3.3µF (ceramic) (ESR ≤ 1.5Ω), C

OUT_TRK

= 10µF (ESR ≤ 1.5Ω), C

REF

= 1000pF, V

OUT_LDO

= 5V, TA= TJ= -40°C to +125°C, unless

otherwise noted. Typical values are at T

= +25°C.) (Note 1)

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

IN Undervoltage Lockout V

IN Undervoltage Lockout Hysteresis

Internal Voltage Reference REF I

Internal Voltage Reference Maximum Current

Thermal-Shutdown Temperature

Thermal Hysteresis T

LDO

Output Voltage V

FB_LDO Set-Point Voltage V

Dual Mode™ FB_LDO Threshold

FB_LDO Input Current I

LDO Output Voltage Range V

LDO Dropout Voltage (Note 3)

LDO Output Current I

LDO Output Current Limit I

OUT_LDO Line Regulation

OUT_LDO Load Regulation

OUT_LDO Power-Supply Rejection Ratio

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

UVLO_HYST

OUT_LDO

UVLO

REF

SHDN

HYST

VIN falling, GATE disabled 4.10 4.27 4.45 V

= 0µA 1.21 1.235 1.26 V

REF

ΔV

REF

= 1mA, FB_LDO = SGND 4.92 5 5.09

LOAD

= ±200mV -6 +6 µA

= 300mA, VIN = 8V,

FB_LDO = SGND

FB_LDO

FB_LDO_TH

FB_LDO

LDO_ADJ

OUT_LDO

LIM_LDO

ΔV

OUT

ΔV

With respect to SGND, I V

OU T _L D O

= 5V ( ad j ustab l e outp ut op ti on)

FB_LDO rising 0.125

FB_LDO falling 0.064

= 1V -100 +100 nA

FB_LDO

Adjustable output option (Note 2) 1.8 11.0 V

= 300mA 775 1500

LOAD

= 200mA 520 1000

LOAD

(Note 4) 300 mA

OUT_LDO = GND, VIN = 6V 330 500 700 mA

6V ≤ VIN ≤ 40V, I V

6V ≤ VIN ≤ 40V, I

OUT_LDO

LOAD

= 5V

LOAD

= 3.3V

LOAD

FB_LDO = SGND, V

6V ≤ VIN ≤ 40V, I V

OUT_LDO

LOAD

= 3.3V

1mA to 300mA, VIN = 8V,

ΔV

ΔI

PSRR

OUT

FB_LDO = SGND, V

1mA to 300mA, VIN = 6.3V, V

OUT_LDO

LOAD

OUT_LDO

= 3.3V

= 10mA, f = 100Hz, 500mV

= 22µF, V

= 1mA,

LOAD

= 1mA,

= 20mA,

OUT_LDO

= 5V

= 20mA,

OUT_LDO

= 5V

P-P

260 mV

+160 °C

20 °C

4.80 5 5.11

1.21 1.235 1.26 V

0.03 0.2

0.03 0.1

mV/V

0.27 1

0.27 0.5

0.054 0.15

mV/mA

0.038 0.1

60 dB

Page 4

MAX15008/MAX15010

Automotive 300mA LDO Voltage Regulators with Tracker Output and Overvoltage Protector

4 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS (continued)

(VIN= V

TRACK

= +14V, V

SGND

= V

PGND

= 0V, C

GATE

= 6000pF, CIN= 10µF (ESR ≤ 1.5Ω), C

OUT_LDO

= 22µF (ceramic), C

TRACK

3.3µF (ceramic) (ESR ≤ 1.5Ω), C

OUT_TRK

= 10µF (ESR ≤ 1.5Ω), C

REF

= 1000pF, V

OUT_LDO

= 5V, TA= TJ= -40°C to +125°C, unless

otherwise noted. Typical values are at T

= +25°C.) (Note 1)

OUT_LDO Startup Delay Time

OUT_LDO Overvoltage Protection Threshold

OUT_LDO Overvoltage Protection Sink Current

ENABLE/HOLD INPUTS

EN_LDO, EN_PROT, EN_TRK Input Threshold Voltage

EN_LDO, EN_PROT, EN_TRK Input Pulldown Current

HOLD Input Threshold Voltage

HOLD Input Pullup I

RESET

RESET Voltage Threshold High

RESET Voltage Threshold Low

OUT_LDO

CT Ramp Current I

CT Ramp Threshold V

RESET Output-Voltage Low V RESET Open-Drain

Leakage Current

LOAD DUMP PROTECTOR (MAX15008 only)

FB_P ROT Thr eshol d V ol tag eV

FB_PROT Threshold Hysteresis

FB_PROT Input Current I

Startup Response Time t

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

STARTUP_DELAY

OUT_LDO

to 10% of V

= 0mA, from EN_LDO rising

OUT_LDO

(nominal),

30 µs

FB_LDO = SGND

OV_TH

EN_PD

HOLD_PU

1mA sink from OUT_LDO 105 110 %V

OUT_LDO

= V

(nominal) x 1.15 8 19 mA

OUT

0.7

EN_ is internally pulled low to SGND 1 µA

1.4

0.4

HOLD is internally pulled high to OUT_LDO

0.6 µA

RESET goes HIGH when rising

90.0 92.5 95.0 %V

RESET_H

OUT_LDO

crosses this threshold,

FB_LDO = SGND RESET goes HIGH when rising

OUT_LDO

crosses this threshold

RESET goes LOW when falling

88 90 92 %V

4%V

20 µs

to RESET Delay t

R ES ET _L

RESET_FALL

CT_TH

LEAK_RESET

TH_PROT

HYST

FB_PROT

START

OUT_LDO

crosses this threshold,

FB_LDO = SGND RESET goes LOW when falling

OUT_LDO

crosses this threshold

falling, 0.1V/µs 19 µs

VCT = 0V 1.50 2.0 2.35 µA

VCT rising 1.19 1.235 1.27 V

= 1mA, output asserted 0.1 V

SINK

Output not asserted 150 nA

FB_PROT rising 1.20 1.235 1.27 V

FB_PROT

= 1.4V -100 +100 nA

EN_PROT rising, EN_LDO = IN, to

= 0.5V

GATE

OUT_LDO

FB_LDO

OUT_LDO

FB_LDO

TH_PROT

Page 5

MAX15008/MAX15010

Automotive 300mA LDO Voltage Regulators

with Tracker Output and Overvoltage Protector

_______________________________________________________________________________________ 5

ELECTRICAL CHARACTERISTICS (continued)

(VIN= V

TRACK

= +14V, V

SGND

= V

PGND

= 0V, C

GATE

= 6000pF, CIN= 10µF (ESR ≤ 1.5Ω), C

OUT_LDO

= 22µF (ceramic), C

TRACK

3.3µF (ceramic) (ESR ≤ 1.5Ω), C

OUT_TRK

= 10µF (ESR ≤ 1.5Ω), C

REF

= 1000pF, V

OUT_LDO

= 5V, TA= TJ= -40°C to +125°C, unless

otherwise noted. Typical values are at T

= +25°C.) (Note 1)

Note 1: Limits to -40°C are guaranteed by design. Note 2: 1.8V is the minimum limit for proper HOLD functionality. Note 3: Dropout is defined as V

- V

OUT_LDO

when V

OUT_LDO

is 98% of the value of V

OUT_LDO

for VIN= V

OUT_LDO

+ 1.5V.

Note 4: Maximum output current may be limited by the power dissipation of the package.

GATE Rise Time t

FB_PROT to GATE Turn-Off Propagation Delay

GATE Output High Voltage V

GATE Output Pulldown Current

GATE C har g e- P um p C ur r ent I

GATE-to-SOURCE Clamp Voltage

TRACKER

Tracker Supply Voltage Range

ADJ, FB_TRK Input Voltage V

Tracker Output CommonMode Range

Tracking Accuracy Over Line

Tracking Accuracy Over Load

ADJ, FB_TRK Input Current I

Dropout Voltage V

Tracker Output Current I

Output Current Limit I

Current Consumption I

OUT_TRK Power-Supply Rejection Ratio

OUT_TRK Reverse Current I

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

GATE

GATEPD

GATE

CLMP

TRACK

ADJ, VFB_TRK

ΔV

Q_LINE

ΔV

Q_LOAD

FB_TRK, IADJ

OUT_TRK

OUT_TRK_LIM

GATE rising to +8V, V

FB_P ROT step fr om V to V

TH_PROT

SOURCE

GATE

SOURCE

GATE

+ 250mV

= VIN = 5.5V,

to IN = 1MΩ

= VIN; VIN ≥ 14V,

to IN = 1MΩ

= 5V, V

EN_PROT

GATE = SGND 45 µA

OUT_LDO

OUT_TRK

ΔV

TRACK

50mA, V ΔV

FB_TRK

OUT_TRK

ADJ

OUT_TRK

IQ = I 50mA, V

= 20mA, V

= 5V, V

= V

FB_TRK

- V

= 6V, 0.1mA ≤ I

= V

ADJ

FB_TRK

= V

ADJ

- V

= V

= 5V, I

= V

OUT_TRK

= 0V 85 100 115 mA

- I

TRACK

ADJ

OUT_TRK

= V

= EN_PROT = SGND, EN_TRK = IN

PSRR

OUT_TRK_REVERSE

OUT_LDO

500mV V

ADJ

TRACK

40V, V

= 10mA, f = 100Hz,

, V

OUT_TRK

P-P

= 5V

= 14V, V

= 5V

ADJ

SOURCE

T H _ P R OT

= 0V 1 ms

- 250m V

IN +

3.2

IN +

7.0

0.6 µs

IN +

3.5

IN +

8.1

IN +

3.8

IN +

9.5

= 0V 63 100 mA

12 16 18 V

540V

TRACK

- 0.5

TRACK

- 0.5

FB_TRK

TRACK

ADJ

OUT_TRK

ADJ

= 6V to 28V,

OUT_TRK

≤

= 5V,

1.1

-3 +3 mV

= 5V 0.03 0.2 µA

OUT_TRK

= 50mA 0.28 0.5 V

= 5V 50 mA

FB_TRK

= V

OUT_TRK

, I

OUT_TRK

= 5V, EN_LDO

FB_TRK

= V

FB_TRK

2.7 6 mA

60 dB

10 µA

Page 6

MAX15008/MAX15010

Automotive 300mA LDO Voltage Regulators with Tracker Output and Overvoltage Protector

6 _______________________________________________________________________________________

Typical Operating Characteristics

(VIN= V

EN_

= +14V, CIN= 10µF, C

OUT_LDO

= 22µF, C

TRACK

= C

OUT_TRK

= 10µF, V

OUT_LDO

= 5V, FB_LDO = SGND, TA= +25°C,

unless otherwise specified.)

LDO GROUND CURRENT

vs. LOAD CURRENT

MAX15008 toc01

LOAD CURRENT (mA)

0 0.3 0.6 0.90.1 0.4 0.70.2 0.5 0.8 1.0

58 56

GROUND CURRENT (μA)

TA = -40°C

TA = +25°C

TA = +85°C

TA = +125°C

LDO GROUND CURRENT

vs. LOAD CURRENT

MAX15008 toc02

LOAD CURRENT (mA)

0 75 150 22525 100 17550 125 200 250 275 300

100

110

GROUND CURRENT (μA)

TA = +25°C

TA = -40°C

TA = +85°C

TA = +125°C

SHUTDOWN SUPPLY CURRENT

vs. TEMPERATURE

MAX15008 toc03

TEMPERATURE (°C)

20 40-40 100-60 12080060-20 140

SHDN

(μA)

LDO POWER-SUPPLY REJECTION RATIO

MAX15008 toc04

FREQUENCY (Hz)

0.01 1010.1 100 1000

-10

-20

-30

-40

-50

-60

-70

PSRR (dB)

OUT_LDO

= 10mA

TRACKER POWER-SUPPLY REJECTION RATIO

MAX15008 toc05

FREQUENCY (kHz)

0.1 101 100 1000

-10

-20

-30

-40

-50

-60

-70

TRACKER PSRR (dB)

OUT_LDO

= 10mA

VIN UVLO HYSTERESIS

vs. TEMPERATURE

MAX15008 toc06

TEMPERATURE (°C)

-50 7525-25 125500 100 150

400

350

300

250

200

150

100

UVLO HYSTERESIS (mV)

REF VOLTAGE

vs. TEMPERATURE

MAX15008 toc07

TEMPERATURE (°C)

-50 7525-25 125500 100 150

1.245

1.240

1.235

1.230

1.225

1.220

REF

(V)

LDO OUTPUT VOLTAGE

vs. INPUT VOLTAGE

MAX15008 toc08

VIN (V)

02010 30 40

OUT_LDO

(V)

OUT_LDO

= 10mA

OUT_LDO

= 300mA

(PULSED)

Page 7

MAX15008/MAX15010

Automotive 300mA LDO Voltage Regulators

with Tracker Output and Overvoltage Protector

_______________________________________________________________________________________

Typical Operating Characteristics (continued)

(VIN= V

EN_

= +14V, CIN= 10µF, C

OUT_LDO

= 22µF, C

TRACK

= C

OUT_TRK

= 10µF, V

OUT_LDO

= 5V, FB_LDO = SGND, TA= +25°C,

unless otherwise specified.)

LDO LOAD-TRANSIENT RESPONSE

2ms/div

TRACKER LOAD-TRANSIENT RESPONSE

400μs/div

MAX15008 toc09

MAX15008 toc12

OUT_LDO

100mA/div 0A

OUT_LDO

5V, AC-COUPLED 20mV/div

OUT_TRK

50mA/div 0A

OUT_TRK

5V, AC-COUPLED 20mV/div

LDO LOAD-TRANSIENT RESPONSE

-0.5

-1.0

(mV)

-1.5

OUT_TRK

- V

ADJ

-2.0

-2.5

-3.0

400μs/div

TRACKER ACCURACY

vs. LOAD CURRENT

ADJ = OUT_LDO FB_TRK = OUT_TRK

(mA)

OUT_TRK

MAX15008 toc10

50100204030 60 70

OUT_LDO

100mA/div

OUT_LDO

5V, AC-COUPLED 100mV/div

MAX15008 toc13

LDO OUTPUT VOLTAGE

vs. TEMPERATURE

5.10

OUT_LDO

= 100μA I

= 100mA

OUT_LDO

TEMPERATURE (°C)

OUT_LDO

5.05

5.00

(V)

4.95

OUT_LDO

4.90

4.85

4.80

-50 7525-25 125500 100 150

TRACKER ACCURACY (V

vs. TEMPERATURE

= 100μA

OUT_TRK

-1

-2

TRACKER ACCURACY (mV)

= 1mA

OUT_TRK

-3

-4 0 125-75 100755025-25-50 150

TEMPERATURE (°C)

= 300mA

FB_TRK

OUT_TRK

= 10mA

VIN = 8V

= V

= 70mA

MAX15008 toc11

)

ADJ

MAX15008 toc14

20V/div

OUT_LDO

3.3V, AC-COUPLED 50mV/div

OUT_TRK

3.3V, AC-COUPLED

50mV/div

OUT_PROT

20V/div

LINE-TRANSIENT RESPONSE

40ms/div

MAX15008 toc15

10V/div

OUT_LDO

3.3V, AC-COUPLED 20mV/div

OUT_TRK

3.3V, AC-COUPLED

20mV/div

OUT_PROT

10V/div

LINE-TRANSIENT RESPONSE

MAX15008 toc16

40ms/div

Page 8

MAX15008/MAX15010

Automotive 300mA LDO Voltage Regulators with Tracker Output and Overvoltage Protector

8 _______________________________________________________________________________________

Typical Operating Characteristics (continued)

(VIN= V

EN_

= +14V, CIN= 10µF, C

OUT_LDO

= 22µF, C

TRACK

= C

OUT_TRK

= 10µF, V

OUT_LDO

= 5V, FB_LDO = SGND, TA= +25°C,

unless otherwise specified.)

1000

900

800

700

600

500

400

300

LDO DROPOUT VOLTAGE (mV)

200

100

LDO DROPOUT VOLTAGE

vs. LOAD CURRENT

0 200100 300

(mA)

OUT_LDO

MAX15008 toc17

10V/div

RESET

5V/div

OUT_LDO

5V/div

OUT_TRK

5V/div

STARTUP RESPONSE THROUGH V

= 100mA

OUT_LDO

= 100mA

OUT_TRK

EN_LDO = EN_TRK = IN

20ms/div

MAX15008 toc18

STARTUP RESPONSE THROUGH EN

20V/div

EN_LDO

5V/div

RESET

5V/div

OUT_LDO

5V/div

OUT_TRK

5V/div

OUT_LDO

OUT_TRK

EN_TRK

= 100mA

= V

EN_LDO

20ms/div

MAX15008 toc19

SHUTDOWN RESPONSE THROUGH V

10V/div

= 100mA

OUT_LDO

= 70mA

OUT_TRK

= V

EN_TRK

RESET

5V/div

OUT_LDO

5V/div

OUT_TRK

5V/div

EN_LDO

= V

20ms/div

MAX15008 toc20

OUT_LDO

OUT_TRK

SHUTDOWN RESPONSE THROUGH EN

20V/div

EN_LDO

5V/div

RESET

5V/div

GROUND CURRENT DISTRIBUTION

HISTOGRAM (T

NUMBER OF PARTS

696765

GROUND CURRENT (μA)

= -40°C)

7371

77 79

EN_LDO = EN_TRK

= 100mA

OUT_LDO

= 70mA

OUT_TRK

400μs/div

MAX15008 toc23

MAX15008 toc21

EN_LDO

5V/div

OUT_LDO

5V/div

HOLD

5V/div

RESET 5V/div

GROUND CURRENT DISTRIBUTION

HISTOGRAM (T

NUMBER OF PARTS

59 63 67 71 75

51 55

GROUND CURRENT (μA)

LDO, EN_LDO, AND HOLD TIMING

HOLD PULLED UP TO OUT_LDO

200ms/div

= +125°C)

MAX15008 toc24

73 77

6557

MAX15008 toc22

Page 9

MAX15008/MAX15010

Automotive 300mA LDO Voltage Regulators

with Tracker Output and Overvoltage Protector

_______________________________________________________________________________________

Typical Operating Characteristics (continued)

(VIN= V

EN_

= +14V, CIN= 10µF, C

OUT_LDO

= 22µF, C

TRACK

= C

OUT_TRK

= 10µF, V

OUT_LDO

= 5V, FB_LDO = SGND, TA= +25°C,

unless otherwise specified.)

PROTECTOR GATE VOLTAGE

vs. INPUT VOLTAGE (MAX15008 ONLY)

GATE

GATE VOLTAGE (V)

20 2515 30 4010 3550

VIN (V)

OVERVOLTAGE LIMIT FAULT

(MAX15008 ONLY)

20V/div

GATE

20V/div

= 1A

OUT_PROT

OV THRESHOLD = 35V

OUT_PROT

20V/div

40ms/div

MAX15008 toc28

10V/div

MAX15008 toc25

GATE

10V/div

OUT_PROT

10V/div

RESET TIMEOUT DELAY (ms)

PROTECTOR STARTUP RESPONSE

(MAX15008 ONLY)

10ms/div

OUT_PROT

MAX15008 toc26

RESET TIMEOUT DELAY

vs. C

RESET

8621040

(nF)

RESET

= 1A

OVERVOLTAGE SWITCH FAULT

(MAX15008 ONLY)

10V/div

20V/div

OUT_PROT

20V/div

GATE

OUT_PROT

= 25V

= 1A

400μs/div

RESET TIMEOUT DELAY

vs. TEMPERATURE

2.0

1.8

1.6

MAX15008 toc29

RESET TIMEOUT DELAY (ms)

= 2.2nF

RESET

1.4

1.2

1.0

0.8

0.6

0.4

= 220pF

RESET

0.2

-25 250 100 12550 15075-50 TEMPERATURE (°C)

MAX15008 toc27

MAX15008 toc30

Page 10

MAX15008/MAX15010

Automotive 300mA LDO Voltage Regulators with Tracker Output and Overvoltage Protector

10 ______________________________________________________________________________________

Pin Description

MAX15008 MAX15010

1, 2, 8, 11, 23, 24, 26, 27, 28, 31,

3 3 OUT_TRK

4 4 ADJ

5 5 SGND Signal Ground

6 6 PGND

1, 2, 8, 10–13, 18, 23, 24, 26, 27, 28, 31,

NAME FUNCTION

N.C. No Connection. Not internally connected.

Tracker Output. Bypass OUT_TRK to SGND with a 10µF (min) capacitor with low ESR (≤ 1.5Ω).

Tracker Amplifier Input. Connect ADJ to OUT_LDO or to an external source to track. Alternatively, connect ADJ to REF to provide the reference voltage to the tracker.

Ground. PGND is also the return path for the overvoltage protector pulldown current for the MAX15008. In this case, connect PGND to SGND at the negative terminal of the bypass capacitor connected to the source of the external MOSFET. For the MAX15010, connect PGND to SGND together to the local ground plane.

77RESET

99CT

10 — FB_PROT

12 — GATE

13 — SOURCE

14 14 REF 1.235V Voltage Reference Output. Bypass REF to SGND with a 1nF or larger capacitor.

Active-Low Open-Drain Reset Output. RESET is low while OUT_LDO is below the reset threshold. Once OUT_LDO has exceeded the reset threshold, RESET remains low for the duration of the reset timeout period before going high.

Reset Timeout Adjust Input. Connect a capacitor (C the reset timeout period. See the Setting the

Overvoltage Threshold Adjustment Input. Connect FB_PROT to an external resistive voltage-divider network to adjust the desired overvoltage threshold. Use FB_PROT to monitor a system input or output voltage. See the Setting the Overvoltage Threshold (MAX15008 Only) section.

P r otector Gate D r i ve O utp ut. C onnect GATE to the g ate of an exter nal n- channel M OS FE T. G ATE i s the outp ut of a char g e p um p w i th a 45µA p ul l up cur r ent to 7.1V ( typ ) ab ove IN d ur i ng nor m al op er ati on. GATE i s q ui ckl y tur ned off thr oug h a 63m A i nter nal p ul l d ow n d ur i ng an over vol tag e cond i ti on. G ATE then r em ai ns l ow unti l FB_P RO T has d ecr eased 96% b el ow the thr

Output-Voltage Sense Input. Connect SOURCE to the source of the external n-channel MOSFET.

) from CT to ground to adjust

RESET

Timeout Period section.

eshol d . GATE p ul l s l ow w hen E N _P RO T i s l ow .

Page 11

MAX15008/MAX15010

Automotive 300mA LDO Voltage Regulators

with Tracker Output and Overvoltage Protector

______________________________________________________________________________________ 11

Pin Description (continued)

MAX15008 MAX15010

15 15 FB_LDO

16 16 EN_LDO

17 17 EN_TRK

18 — EN_PROT

19, 20 19, 20 IN Regulator Input. Bypass IN to SGND with a 10µF capacitor (ESR ≤ 1.5Ω).

21, 22 21, 22 OUT_LDO

25 25 HOLD

NAME FUNCTION

LDO Voltage Feedback Input. Connect FB_LDO to SGND to select the preset +5V output voltage. Connect FB_LDO to an external resistive voltage-divider for adjustable output operation. See the Setting the Output Voltage section.

Active-High LDO Enable Input. Connect EN_LDO to IN or to a logic-high voltage to turn on the regulator. To place the LDO in shutdown, pull EN_LDO low or leave unconnected and leave HOLD unconnected. EN_LDO is internally pulled to SGND through a 1µA current sink. See the Control Logic section.

Active-High Tracker Enable Input. Connect EN_TRK to IN or to a logic-high voltage to turn on the tracker. Pull EN_TRK low or leave unconnected to place tracker in shutdown. EN_TRK is internally pulled to SGND through a 1µA current sink.

Protector Enable Input. Drive EN_PROT low to force GATE low and turn off the external n-channel MOSFET. EN_PROT is internally pulled to SGND by a 1µA sink. Connect EN_PROT to IN for normal operation.

LDO Regulator Output. Bypass OUT_LDO to SGND with a low-ESR capacitor with a minimum value of 22µF. Fixed +5V or adjustable output (+1.8V to +11V). See the Setting the Output Voltage section.

Active-Low Hold Input. If EN_LDO is high when HOLD is forced low, the regulator latches the state of the EN_LDO input and allows the regulator to remain turned on when EN_LDO is subsequently pulled low. To shut down the regulator, release HOLD after EN_LDO is pulled low. If HOLD functionality is unused, connect HOLD to OUT_LDO or leave unconnected. HOLD is internally pulled up to OUT_LDO through a

0.6µA current source. See the Control Logic section.

29 29 FB_TRK

30 30 TRACK Tracker Input. Bypass TRACK to the SGND with a 3.3µF ceramic capacitor.

EP EP EP

Tracker Amplifier Feedback. Connect FB_TRK directly to OUT_TRK or through an external resistive voltage-divider.

Exposed Pad. Connect EP to SGND plane. EP also functions as a heatsink to maximize thermal dissipation. Do not use as the main ground connection.

Page 12

MAX15008/MAX15010

Automotive 300mA LDO Voltage Regulators with Tracker Output and Overvoltage Protector

12 ______________________________________________________________________________________

Functional Diagram

ENABLE LDO

HOLD

-20V TO +40V

5V TO 40V

EN_LDO

HOLD

REF

TRACK

CONTROL

LOGIC

BIAS AND VOLTAGE

REFERENCE

REF

0.92 x V

REF

REVERSE-BATTERY

ADJ

PROTECTION

LDO

2μA

REF

1.235V

TRACKER

REF

5V LDO

OUT_LDO

M U

FB_LDO

0.125V

RESET

OUT_TRK

OUTPUT

RESET OUTPUT

TRACKER OUTPUT

ENABLE

TRACKER

ENABLE

PROTECTOR

EN_TRK

EN_PROT

GATE UVLO

4.75V

REF

OVERVOLTAGE PROTECTOR

(MAX15008 ONLY)

EP SGND PGND

FB_TRK

GATE

SOURCE

FB_PROT

PROTECTOR OUTPUT

Page 13

Detailed Description

The MAX15008/MAX15010 integrate a 300mA LDO voltage regulator, a voltage tracker, and an OVP controller. These devices operate over a wide 5V to 40V supply voltage range and are able to withstand loaddump transients up to 45V.

The MAX15008/MAX15010 feature a 300mA LDO regulator that consumes less than 70µA of current under light-load conditions and feature a fixed 5V or an adjustable output voltage (1.8V to 11V). Connect FB_LDO to ground to select a fixed 5V output voltage or select the LDO output voltage by connecting an external resistive voltage-divider at FB_LDO. The regulator sources at least 300mA of current and includes a current limit of 330mA (min). Enable the LDO by pulling EN_LDO high.

The tracker can be powered from the LDO input supply voltage or an independent voltage source. It is designed to supply power to a remote sensor and is able to handle the severe conditions in automotive applications. Set the tracker output voltage by connecting a resistive voltage-divider to OUT_TRK and connecting ADJ to the tracking source. The tracker feedback, FB_TRK, and a separate tracker reference voltage input, ADJ, offer the flexibility of setting the tracker output to be lower, equal to, or higher than the main (LDO) output. Pull EN_TRK to SGND to turn the tracker off and keep the device in always-on, lowquiescent-current operation.

The OVP controller (MAX15008 only) relies on an external MOSFET with adequate voltage rating (V

DSS

) to protect downstream circuitry from overvoltage transients. The OVP controller drives the gate of the external n-channel MOSFET, and is configurable to operate as an overvoltage protection switch or as a closed-loop voltage limiter.

GATE Voltage (MAX15008 Only)

The MAX15008 uses a high-efficiency charge pump to generate the GATE voltage for the external n-channel MOSFET. Once the input voltage, VIN, exceeds the undervoltage lockout (UVLO) threshold, the internal charge pump fully enhances the external n-channel MOSFET. An overvoltage condition occurs when the voltage at FB_PROT goes above the threshold voltage, V

TH_PROT

. After V

TH_PROT

is exceeded, GATE is quickly pulled to PGND with a 63mA pulldown current. The MAX15008 includes an internal clamp from GATE to SOURCE that ensures that the voltage at GATE never exceeds one diode drop below SOURCE during gate

discharge. The voltage clamp also prevents the GATEto-SOURCE voltage from exceeding the absolute maximum rating for the V

of the external MOSFET in case

the source terminal is accidentally shorted to 0V.

Overvoltage Monitoring (MAX15008 Only)

The OVP controller monitors the voltage at FB_PROT and controls an external n-channel MOSFET, isolating, or limiting the load during an overvoltage condition. Operation in OVP switch mode or limiter mode depends on the connection between FB_PROT and the external MOSFET.

Overvoltage Switch Mode

When operating in OVP switch mode, the FB_PROT divider is connected to the drain of the external MOSFET. The feedback path consists of the voltagedivider tapped at FB_PROT, FB_PROT’s internal comparator, the internal gate charge pump/gate pulldown, and the external n-channel MOSFET (Figure

1). When the programmed overvoltage threshold is exceeded, the internal comparator quickly pulls GATE to ground and turns off the external MOSFET, disconnecting the power source from the load. In this configuration, the voltage at the source of the MOSFET is not monitored. When the voltage at FB_PROT decreases below the overvoltage threshold, the MAX15008 raises the voltage at GATE, reconnecting the load to the power source.

MAX15008/MAX15010

Automotive 300mA LDO Voltage Regulators

with Tracker Output and Overvoltage Protector

______________________________________________________________________________________ 13

Figure 1. Overvoltage Switch Configuration (MAX15008)

FB_PROT

MAX15008

SGND

GATE

PROTECTOR

OUTPUT

SOURCE

Page 14

MAX15008/MAX15010

Automotive 300mA LDO Voltage Regulators with Tracker Output and Overvoltage Protector

14 ______________________________________________________________________________________

Overvoltage-Limiter Mode

When operating in overvoltage-limiter mode, the feedback path consists of SOURCE, FB_PROT’s internal comparator, the internal gate charge pump/gate pulldown, and the external n-channel MOSFET (Figure 2). This configuration results in the external MOSFET operating as a hysteretic voltage regulator.

During normal operation, GATE is enhanced 8.1V above VIN. The external MOSFET source voltage is monitored through a resistive voltage-divider between SOURCE and FB_PROT. When V

SOURCE

exceeds the adjustable overvoltage threshold, an internal pulldown switch discharges the gate voltage and quickly turns the MOSFET off. Consequently, the source voltage begins to fall. The V

SOURCE

fall time is dependent on the MOSFET’s gate charge, the internal charge-pump current, the output load, and any load capacitance at SOURCE. When the voltage at FB_PROT is below the overvoltage threshold by an amount equal to the hysteresis, the charge pump restarts and turns the MOSFET back on. In this way, the OVP controller attempts to regulate V

SOURCE

around the overvoltage threshold. SOURCE remains high during overvoltage transients and the MOSFET continues to conduct during an overvoltage event. The hysteresis of the FB_PROT comparator and the gate turn-on delay force the external MOSFET to operate in a switched on/off sequence during an overvoltage event.

Exercise caution when operating the MAX15008 in voltage-limiting mode for long durations. Care must be taken against prolonged or repeated exposure to overvoltage events while delivering large amounts of load current as the power dissipation in the external MOSFET may be high under these conditions. To prevent damage to the MOSFET, implement proper heatsinking. The capacitor connected between SOURCE and ground can also be damaged if the ripple current rating for the capacitor is exceeded.

As the transient voltage decreases, the voltage at SOURCE falls. For fast-rising transients and very large MOSFETs, connect an additional capacitor from GATE to PGND. This capacitor acts as a voltage-divider work-

ing against the MOSFET’s drain-to-gate capacitance. If using a very low gate charge MOSFET, additional capacitance from GATE to ground might be required to reduce the switching frequency.

Control Logic

The MAX15008/MAX15010 LDO features two logic inputs, EN_LDO and HOLD, making these devices suitable for automotive applications. For example, when the ignition key signal drives EN_LDO high, the regulator turns on and remains on even if EN_LDO goes low, as long as HOLD is forced low and stays low after initial regulator power-up. In this state, releasing HOLD turns the regulator output (OUT_LDO) off. This feature makes it possible to implement a self-holding circuit without external components. Forcing EN_LDO low and HOLD high (or unconnected) places the regulator into shutdown mode reducing the supply current to less than 16µA. Table 1 shows the state of OUT_LDO with respect to EN_LDO and HOLD. Leave HOLD uncon- nected or connect directly to OUT_LDO to allow the EN_LDO input to act as a standard on/off logic input for the regulator.

Figure 2. Overvoltage Limiter (MAX15008)

MAX15008

SGND

GATE

PROTECTOR

SOURCE

FB_PROT

OUTPUT

Page 15

Applications Information

Load Dump

Most automotive applications run off a multicell 12V lead-acid battery with a nominal voltage that swings between 9V and 16V, depending on load current, charging status, temperature, and battery age, etc. The battery voltage is distributed throughout the automobile and is locally regulated down to voltages required by the different system modules. Load dump occurs when the alternator is charging the battery and the battery becomes disconnected. Power in the alternator (behaving now essentially as an inductor) flows into the distributed power system and elevates the voltage seen at each module. The voltage spikes have rise times typically greater than 5ms and decay within several hundred milliseconds but can extend out to 1s or more depending on the characteristics of the charging system. These transients are capable of destroying semiconductors on the first fault event.

The MAX15008/MAX15010 feature load-dump transient protection up to +45V.

Setting the Output Voltage

The MAX15008/MAX15010 feature dual-mode operation: these devices operate in either a preset voltage mode or an adjustable mode. In preset voltage mode, internal feedback resistors set the linear regulator out-

put voltage (V

OUT_LDO

) to 5V. To select the preset 5V

output voltage, connect FB_LDO to SGND.

To select an adjustable output voltage between 1.8V and 11V, use two external resistors connected as a voltage-divider to FB_LDO (Figure 3). Set the output voltage using the following equation:

OUT_LDO

= V

FB_LDO

x (R1 + R2) / R

where V

FB_LDO

= 1.235V and R2≤ 50kΩ.

MAX15008/MAX15010

Automotive 300mA LDO Voltage Regulators

with Tracker Output and Overvoltage Protector

______________________________________________________________________________________ 15

Figure 3. Setting the LDO Output Voltage

Table 1. EN_LDO/

HHOOLLDD

Truth Table/State Table

OPERATION STATE EN_LDO HOLD OUT_LDO COMMENT

Initial State Low Don’t care OFF

Turn-On State High Don’t care ON

Hold Setup State High Low ON

Hold State Low Low ON

Off State Low

EN_LDO is pulled to SGND through an internal pulldown. HOLD is unconnected and is internally pulled up to OUT_LDO. The regulator is disabled.

EN_LDO is externally driven high turning regulator on. HOLD is pulled up to OUT_LDO.

HOLD is externally pulled low while EN_LDO remains high (latches EN_LDO state).

EN_LDO is driven low or left unconnected. HOLD remains externally pulled low keeping the regulator on.

High or

unconnected

OFF

HOLD is driven high or left unconnected while EN_LDO is low. The regulator is turned off and EN_LDO/HOLD logic returns to the initial state.

MAX15008 MAX15010

OUT_LDO

FB_LDO

SGND

Page 16

MAX15008/MAX15010

Setting the

RESET

Timeout Period

The reset timeout period is adjustable to accommodate a variety of applications. Set the reset timeout period by connecting a capacitor, C

RESET

, between CT and SGND. Use the following formula to select the reset timeout period, t

RESET

= C

RESET

x V

CT_TH

/ I

where t

RESET

is in seconds and C

RESET

is in µF.

CT_TH

is the CT ramp threshold in volts and ICTis the

CT ramp current in µA, as described in the

Electrical

Characteristics

table. Leave CT open to select an internally fixed timeout period of 10µs. To maintain reset timeout accuracy, use a low-leakage (< 10nA) type capacitor.

Tracker Input/Feedback Adjustment

The tracker can be powered from the LDO input supply voltage or an independent voltage source. It is designed to supply power to a remote sensor and its supply input, TRACK, is able to handle the severe conditions in automotive applications such as battery reversal and load-dump transients up to 45V.

The tracker feedback, FB_TRK, and a separate tracker reference voltage input, ADJ, offer the flexibility of set-

ting the tracker output to be lower, equal to, or higher than the main (LDO) output. Other external voltages can also be tracked.

Connect ADJ to OUT_LDO and FB_TRK to OUT_TRK to track the LDO output voltage directly (Figure 4a). To track a voltage higher than V

OUT_LDO

, directly connect ADJ to OUT_LDO and connect FB_TRK to OUT_TRK through a resistive voltage-divider (Figure 4b). To track a voltage lower than the LDO regulator output, V

OUT_LDO

, directly connect FB_TRK to OUT_TRK and connect ADJ to OUT_LDO through a resistive voltagedivider (Figure 4c). To track an external voltage VXwith a generic attenuation/amplification ratio, connect resistive voltage-dividers between ADJ and the voltage input or output to be tracked (VX), and between OUT_TRK and FB_TRK (Figure 4d). Pay attention to the resistive loading of the voltage VXdue to the divider R5, R6.

To track the internal REF voltage (1.235V), directly connect ADJ to REF. The voltage at FB_TRK or ADJ should be greater than or equal to 1.1V and less than V

TRACK

- 0.5V. Resistors should have a tolerance of 1% or better. Their values should be low enough to ensure that the divider current is at least 100x the maximum input bias current at pins FB_TRK and ADJ (I

FB_TRK_ADJ

, max = 0.2µA).

Automotive 300mA LDO Voltage Regulators with Tracker Output and Overvoltage Protector

16 ______________________________________________________________________________________

Figure 4. Tracker Input and Feedback Adjustment

TRACK

TO TRACK V V

OUT_TRK

TRACK

TO TRACK A VOLTAGE LOWER THAN V

OUT_TRK

= V

R5 + R6 < V

MAX15008 MAX15010

OUT_LDO

= V

OUT_LDO

(a)

MAX15008 MAX15010

x R6 / (R5 + R6),

OUT_LDO

(c)

OUT_LDO

OUT_TRK

FB_TRK

OUT_LDO

OUT_TRK

FB_TRK

/ 20μA

ADJ

OUT_LDO

LDO OUTPUT

TRACKER OUTPUT

LDO OUTPUT

TRACKER OUTPUT

MAX15008 MAX15010

TRACK

TO TRACK A VOLTAGE HIGHER THAN

OUT_TRK

TO TRACK A GENERIC VOLTAGE V

= VX x (R6 / (R5 + R6)) x ((R3 + R4) / R4),

OUT_TRK

R5 + R6 < V

OUT_LDO

= V

OUT_LDO

R3 + R4 < V

OUT_TRK

(b)

MAX15008 MAX15010

TRACK

/ 20μA, R3 + R4 < V

(d)

OUT_LDO

ADJ

OUT_TRK

FB_TRK

x (R3 + R4) / R4,

/ 20μA

ADJ

OUT_TRK

FB_TRK

OUT_TRK

/ 20μA

LDO OUTPUT

TRACKER OUTPUT

Page 17

Setting the Overvoltage Threshold

(MAX15008 Only)

The MAX15008 provides an accurate means to set the overvoltage threshold for the OVP controller using FB_PROT. Use a resistive voltage-divider to set the desired overvoltage threshold (Figure 5). FB_PROT has a rising 1.235V threshold with a 4% falling hysteresis.

Begin by selecting the total end-to-end resistance, R

TOTAL

= R5+ R6. Choose R

TOTAL

to yield a total cur-

rent equivalent to a minimum of 100 x I

FB_PROT

(FB_PROT’s input maximum bias current) at the desired overvoltage threshold. See the

Electrical

Characteristics

table.

For example:

With an overvoltage threshold (VOV) set to 20V, R

TOTAL

< 20V / (100 x I

FB_PROT

), where I

FB_PROT

FB_PROT’s maximum 100nA bias current:

TOTAL

< 2MΩ

Use the following formula to calculate R6:

R6= V

TH_PROT

x R

TOTAL

/ V

where V

TH_PROT

is the 1.235V FB_PROT rising threshold and VOVis the desired overvoltage threshold. R6= 124kΩ:

TOTAL

= R5+ R

where R5= 1.88MΩ. Use a standard 1.87MΩ resistor.

A lower value for total resistance dissipates more power, but provides better accuracy and robustness against external disturbances.

Input Transients Clamping

When the external MOSFET is turned off during an overvoltage event, stray inductance in the power path may cause additional input-voltage spikes that exceed the V

DSS

rating of the external MOSFET or the absolute maximum rating for the MAX15008 (IN, TRACK). Minimize stray inductance in the power path using wide traces and minimize the loop area included by the power traces and the return ground path.

For further protection, add a zener diode or transient voltage suppressor (TVS) rated below the absolute maximum rating limits (Figure 6).

MAX15008/MAX15010

Automotive 300mA LDO Voltage Regulators

with Tracker Output and Overvoltage Protector

______________________________________________________________________________________ 17

Figure 5. Setting the Overvoltage Threshold (MAX15008)

Figure 6. Protecting the MAX15008 Input from High-Voltage Transients

TVS

MAX15008

GATE

SOURCE

SGND

LOAD

MAX15008

FB_PROT

SGND

GATE

SOURCE

PROTECTOR

OUTPUT

MAX15008

SGND

GATE

SOURCE

FB_PROT

PROTECTOR

OUTPUT

Page 18

MAX15008/MAX15010

External MOSFET Selection

Select the external MOSFET with adequate voltage rating, V

DSS

, to withstand the maximum expected loaddump input voltage. The on-resistance of the MOSFET, R

DS(ON)

, should be low enough to maintain a minimal voltage drop at full load, limiting the power dissipation of the MOSFET.

During regular operation, the power dissipated by the MOSFET is:

NORMAL

= I

LOAD

x R

DS(ON)

Normally, this power loss is small and is safely handled by the MOSFET. However, when operating the MAX15008 in overvoltage-limiter mode under prolonged or frequent overvoltage events, select an external MOSFET with an appropriate power rating.

During an overvoltage event, the power dissipation in the external MOSFET is proportional to both load current and to the drain-source voltage, resulting in high power dissipated in the MOSFET (Figure 7). The power dissipated across the MOSFET is:

OV_LIMITER

= VQ1x I

LOAD

where VQ1is the voltage across the MOSFET’s drain and source during overvoltage-limiter operation, and I

LOAD

is the load current.

Overvoltage-Limiter Mode

Switching Frequency

When the MAX15008 is configured in overvoltagelimiter mode, the external n-channel MOSFET is subse-

quently switched on and off during an overvoltage event. The output voltage at SOURCE resembles a periodic sawtooth waveform. Calculate the period of the waveform, t

OVP

, by summing three time intervals

(Figure 8):

OVP

= t1+ t2+ t

where t1is the V

SOURCE

output discharge time, t2 is the

GATE delay time, and t

is the V

SOURCE

output charge time.

During an overvoltage event, the power dissipated inside the MAX15008 is due to the gate pulldown current, I

GATEPD

. This amount of power dissipation is

worse when I

SOURCE

= 0 (C

SOURCE

is discharged only

by the internal current sink).

The worst-case internal power dissipation contribution in overvoltage-limiter mode, P

OVP

, in watts can be

approximated using the following equation:

where VOVis the overvoltage threshold voltage in volts and I

GATEPD

is the 63mA (typ) GATE pulldown current.

Output Discharge Time (t1)

When the voltage at SOURCE exceeds the adjusted overvoltage threshold, GATE’s internal pulldown is enabled until V

SOURCE

drops by 4%. The internal cur-

rent sink, I

GATEPD

, and the external load current,

LOAD

, discharge the external capacitance from

SOURCE to ground.

Automotive 300mA LDO Voltage Regulators with Tracker Output and Overvoltage Protector

18 ______________________________________________________________________________________

Figure 8. MAX15008 Timing Diagram

Figure 7. Power Dissipated Across MOSFETs During an Overvoltage Fault (Overvoltage Limiter Mode)

MAX

GATE

+ VQ1 -

LOAD

SOURCE

PV I

=×× ×0981.

OVP OV GATEPD

OVP

TVS

MAX15008

FB_PROT

SGND

SOURCE

LOAD

GATE

SOURCE

OVP

Page 19

Calculate the discharge time, t1, using the following equation:

where t1is in ms, VOVis the adjusted overvoltage threshold in volts, I

LOAD

is the external load current in

mA, and I

GATEPD

is the 63mA (typ) internal pulldown

current of GATE. C

SOURCE

is the value of the capacitor connected between the source of the MOSFET and PGND in µF.

GATE Delay Time (t2)

When SOURCE falls 4% below the overvoltage threshold voltage, the internal current sink is disabled and the internal charge pump begins recharging the external GATE voltage. Due to the external load, the SOURCE voltage continues to drop until the gate of the MOSFET is recharged. The time needed to recharge GATE and reenhance the external MOSFET is approximately:

where t2is in µs, C

iss

is the input capacitance of the

MOSFET in pF, and V

GS(TH)

is the gate-to-source threshold voltage of the MOSFET in volts. VFis the 0.7V (typ) internal clamp diode forward voltage of the MOSFET in volts, and I

GATE

is the charge-pump current 45µA (typ). Any external capacitance between GATE and PGND will add up to C

iss

During t2, the SOURCE capacitance, C

SOURCE

, loses charge through the output load. The voltage across C

SOURCE

decreases by ΔV2 until the MOSFET reaches

its V

GS(TH)

threshold. Approximate ΔV2using the fol-

lowing formula:

SOURCE Output Charge Time (t3)

Once the GATE voltage exceeds the gate-to-source threshold, V

GS(TH)

, of the external MOSFET, the MOSFET turns on and the charge through the internal charge pump with respect to the drain potential, QG, determines the slope of the output-voltage rise. The time required for the SOURCE voltage to rise again to the overvoltage threshold is:

where ΔV

SOURCE

= (VOVx 0.04) + ΔV2 in volts, and

rss

is the MOSFET’s reverse transfer capacitance in pF. Any external capacitance between GATE and PGND adds up to C

rss

Power Dissipation/Junction Temperature

During normal operation, the MAX15008/MAX15010 has two main sources of internal power dissipation: the LDO and the voltage tracker.

Calculate the power dissipation due to the LDO as:

LDO

= (VIN- V

OUT_LDO

) x I

OUT_LDO

where VINis the LDO input supply voltage in volts, V

OUT_LDO

is the output voltage of the LDO in volts, and

OUT_LDO

is the LDO total load current in mA.

Calculate power dissipation due to the tracker as:

TRK

= (V

TRACK

- V

OUT_TRK

) x I

OUT_TRK

where V

TRACK

is the tracker input supply voltage in

volts, V

OUT_TRK

is the output voltage of the tracker in

volts, and I

OUT_TRK

is the tracker load current in mA.

The total power dissipation P

DISS

in mW as:

DISS

= P

LDO

+ P

TRK

For prolonged exposure to overvoltage events, use the VINand V

TRACK

voltages expected during overvoltage conditions. Under these circumstances the corresponding internal power dissipation contribution, P

OVP

calculated in the

Overvoltage-Limiter Mode Switching

Frequency

section should also be included in the total

power dissipation, P

DISS

For a given ambient temperature, TA, calculate the junction temperature, TJ, as follows:

TJ= TA+ P

DISS

x θ

where TJand TAare in °C and θJAis the junction-toambient thermal resistance in °C/W as listed in the

Absolute Maximum Ratings

section.

The junction temperature should never exceed +150°C during normal operation.

Thermal Protection

When the junction temperature exceeds TJ= +160°C, the MAX15008/MAX15010 shut down to allow the device to cool. When the junction temperature drops to +140°C, the thermal sensor turns all enabled blocks on again, resulting in a cycled output during continuous thermal-overload conditions. Thermal protection protects the MAX15008/MAX15010 from excessive power dissipation. For continuous operation, do not exceed the absolute maximum junction temperature rating of +150°C.

MAX15008/MAX15010

Automotive 300mA LDO Voltage Regulators

with Tracker Output and Overvoltage Protector

______________________________________________________________________________________ 19

0.04 V

=×

1 SOURCE

LOAD GATEPD

=×

iss

()

GS TH F

GATE

ΔV

LOAD

SOURCE

×Δ

rss SOURCE

GATE

Page 20

MAX15008/MAX15010

Automotive 300mA LDO Voltage Regulators with Tracker Output and Overvoltage Protector

20 ______________________________________________________________________________________

Typical Operating Circuits

GATE

5V TO 40V INPUT

TRACK

SOURCE FB_PROT

TRACK

MAX15008

EN_LDOLDO ON/OFF

EN_PROTPROTECTOR ON/OFF

5V TO 40V INPUT

TRACK

EN_TRKTRACKER ON/OFF

HOLDHOLD

CT REF SGND

RESET

TRACK

REF

MAX15010

EN_LDOLDO ON/OFF

EN_TRKTRACKER ON/OFF

HOLDHOLD REF

REF

CT PGND SGND

RESET

PGND

OUT_TRK

FB_TRK

ADJ

OUT_LDO

FB_LDO

RESET

FB_TRK

OUT_TRK

ADJ

OUT_LDO

FB_LDO

RESET

SOURCE

OUT_TRK

DC-DC

MAX5073

TRACKER OUTPUT

OUT_LDO

OUT_TRK

OUT_LDO

300mA

TRACKER OUTPUT

300mA

RESET/EN I/O

50mA

RESET/EN I/O

μC

OUT1

OUT2

Page 21

MAX15008/MAX15010

Automotive 300mA LDO Voltage Regulators

with Tracker Output and Overvoltage Protector

______________________________________________________________________________________ 21

Chip Information

PROCESS: BiCMOS

MAX15010

TQFN

(5mm x 5mm)

TOP VIEW

N.C.

ADJ

SGND

PGND

RESET

N.C.

OUT_LDO

N.C.

4567

2324 22 20 19 18

FB_TRK

TRACK

REF

N.C.

OUT_TRK

OUT_LDO

N.C.

FB_LDO

*EP

*EP = EXPOSED PAD

N.C.

EN_LDO

N.C.

EN_TRK

HOLD

Pin Configurations (continued)

Page 22

MAX15008/MAX15010

Automotive 300mA LDO Voltage Regulators with Tracker Output and Overvoltage Protector

22 ______________________________________________________________________________________

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

QFN THIN.EPS

Page 23

MAX15008/MAX15010

Automotive 300mA LDO Voltage Regulators

with Tracker Output and Overvoltage Protector

______________________________________________________________________________________ 23

Package Information (continued)

(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

Page 24

MAX15008/MAX15010

Automotive 300mA LDO Voltage Regulators with Tracker Output and Overvoltage Protector

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

Revision History

REVISION

NUMBER

0 9/07 Initial release —

1 1/08

REVISION

DATE

Removed future product asterisks, updated Electrical Characteristics table and Typical Operating Characteristics section.

DESCRIPTION

PAGES

CHANGED

1, 2, 6, 8