MAX16929 [MAXIM]

Automotive TFT-LCD Power Supply with Boost Converter and Gate Voltage Regulators; 车载TFT -LCD电源与升压转换器和栅极电压稳压器
MAX16929
型号: MAX16929
厂家: MAXIM INTEGRATED PRODUCTS    MAXIM INTEGRATED PRODUCTS
描述:

Automotive TFT-LCD Power Supply with Boost Converter and Gate Voltage Regulators
车载TFT -LCD电源与升压转换器和栅极电压稳压器

转换器 栅极 稳压器 CD 升压转换器
文件: 总25页 (文件大小:2347K)
中文:  中文翻译
下载:  下载PDF数据表文档文件
                         
����������������������������������������������������������������� ꢀMaxim Integrated Productsꢀ ꢀ 1  
19-5857; Rev 2; 1/12  
E V A L U A T I O N K I T A V A I L A B L E  
General Description  
Features  
The MAX16929 is a highly integrated power supply for  
automotive TFT-LCD applications. The device integrates  
one buck converter, one boost converter, one 1.8V/3.3V  
regulator controller, and two gate voltage regulators.  
The device comes in several versions to satisfy com-  
mon automotive power-supply requirements (see the  
Ordering Information/Selector Guide table).  
SꢀOperatingꢀVoltageꢀRangeꢀofꢀ4Vꢀtoꢀ28Vꢀ(Buck)ꢀorꢀ  
3Vꢀtoꢀ5.5Vꢀ(Boost)  
SꢀIndependentꢀ28VꢀInputꢀBuckꢀConverterꢀPowersꢀ  
TFTꢀBiasꢀSupplyꢀCircuitryꢀandꢀExternalꢀCircuitry  
SꢀHigh-Powerꢀ(Upꢀtoꢀ6W)ꢀBoostꢀOutputꢀProvidingꢀUpꢀ  
toꢀ18V  
Sꢀ1.8Vꢀorꢀ3.3VꢀRegulatorꢀProvidesꢀ500mAꢀwithꢀ  
Designed to operate from a single 4V to 28V supply or  
5.5V to 28V supply, the device is ideal for automotive  
TFT-LCD applications.  
ExternalꢀnpnꢀTransistor  
SꢀOneꢀPositive-GateꢀVoltageꢀRegulatorꢀCapableꢀofꢀ  
Deliveringꢀ20mAꢀatꢀ28V  
Both the buck and boost converters use spread-spec-  
trum modulation to reduce peak interference and to opti-  
mize EMI performance.  
SꢀOneꢀNegative-GateꢀVoltageꢀRegulator  
SꢀHigh-FrequencyꢀOperation  
2.1MHzꢀ(BuckꢀConverter)  
2.2MHzꢀ(BoostꢀConverter)  
The sequencing input (SEQ) allows flexible sequencing  
of the positive-gate and negative-gate voltage regulators.  
The power-good indicator (PGOOD) indicates a failure  
on any of the converters or regulator outputs. Integrated  
thermal shutdown circuitry protects the device from over-  
heating.  
SꢀFlexibleꢀStand-AloneꢀSequencing  
SꢀTrueꢀShutdown™ꢀBoostꢀConverter  
Sꢀ6µAꢀLow-CurrentꢀShutdownꢀModeꢀ(Buck)  
SꢀInternalꢀSoft-Start  
The MAX16929 is available in a 28-pin TSSOP pack-  
age with exposed pad, and operates over the -40NC to  
+105NC temperature range.  
SꢀOvertemperatureꢀShutdown  
Sꢀ-40NCꢀtoꢀ+105NCꢀOperation  
Applications  
Ordering Information/Selector Guide appears at end of data  
sheet.  
Automotive Dashboards  
Automotive Central Information Displays  
Automotive Navigation Systems  
Typical Application Circuit appears at end of data sheet.  
True Shutdown is a trademark of Maxim Integrated Products, Inc.  
For related parts and recommended products to use with this part, refer to: www.maxim-ic.com/MAX16929.related  
Forꢀpricing,ꢀdelivery,ꢀandꢀorderingꢀinformation,ꢀpleaseꢀcontactꢀMaximꢀDirectꢀatꢀ1-888-629-4642,ꢀ  
orꢀvisitꢀMaxim’sꢀwebsiteꢀatꢀwww.maxim-ic.com.  
                         
����������������������������������������������������������������� ꢀMaxim Integrated Productsꢀ ꢀ 2  
MAX16929  
Automotive TFT-LCD Power Supply with Boost  
Converter and Gate Voltage Regulators  
ABSOLUTEꢀMAXIMUMꢀRATINGS  
INB, ENB to GND..................................................-0.3V to +42V  
BST to GND...........................................................-0.3V to +47V  
BST to LXB ..............................................................-0.3V to +6V  
LXB to GND..............................................................-6V to +42V  
AVL, PGOOD to GND .............................................-0.3V to +6V  
FBB to GND...........................................................-0.5V to +12V  
CP, GH to GND.....................................................-0.3V to +31V  
ENP, DR, FB, GATE, COMPI, FBGH,  
FBGL, REF, SEQ to GND .....................-0.3V to (V  
GND to PGNDP....................................................-0.3V to +0.3V  
+ 0.3V)  
INA  
Continuous Power Dissipation (T = +70NC)  
A
TSSOP (derate 27mW/NC above +70NC)...................2162mW  
Operating Temperature Range........................ -40NC to +105NC  
Junction Temperature Range........................... -40NC to +150NC  
Storage Temperature Range............................ -65NC to +150NC  
Lead Temperature (soldering, 10s) ................................+300NC  
Soldering Temperature (reflow) ......................................+260NC  
CP, GH to GND (V  
= 3.3V) ..............................-0.3V to +29V  
INA  
LXP to GND...........................................................-0.3V to +20V  
DRVN to GND........................................................-25V to +0.3V  
INA, COMPV, FBP to GND......................................-0.3V to +6V  
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional opera-  
tion 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.  
PACKAGEꢀTHERMALꢀCHARACTERISTICS (Noteꢀ1)  
TSSOP  
Junction-to-Ambient Thermal Resistance (B ) ..........37NC/W  
JA  
Junction-to-Case Thermal Resistance (B ).................2NC/W  
JC  
Noteꢀ1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-  
layer board. For detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial.  
ELECTRICALꢀCHARACTERISTICS  
(V  
= 12V, V  
= 5V, V  
= V  
= 0V, T = T = -40NC to +105NC, typical values are at T = +25NC, unless otherwise noted.)  
INB  
INA  
GND  
PGNDP A J A  
(Note 2)  
PARAMETER  
SYMBOL  
CONDITIONS  
MIN  
TYP  
MAX  
UNITS  
BUCKꢀCONVERTER  
V
= 5V (Note 3)  
5.5  
4
28  
28  
42  
9
OUTB  
Supply Voltage Range  
V
V
= 3.3V (Note 3)  
V
INB  
OUTB  
t < 500ms  
V
V
= 0V  
6
ENB  
Supply Current  
I
FA  
INB  
= V , no load, T = +25NC  
70  
ENB  
INB  
A
Undervoltage Lockout  
V
AVL rising  
3.1  
0.5  
2.1  
3.5  
2.3  
V
V
INB,UVLO  
Undervoltage Lockout Hysteresis  
PWM Switching Frequency  
Spread-Spectrum Range  
f
1.9  
MHz  
%
SWB  
SSR  
+6  
5
5V, continuous mode  
5V, skip mode  
P 18V,  
-3%  
-3%  
-3%  
-3%  
+3%  
+6%  
+3%  
+6%  
400  
5
6V P V  
INB  
Output-Voltage Accuracy  
V
V
OUTB  
I
< full load  
3.3V, continuous mode  
3.3V, skip mode  
3.3  
3.3  
180  
LOAD  
High-Side DMOS R  
R
I = 1A  
mI  
DS_ON  
DS_ON(LXB) LXB  
Skip-Current Threshold  
I
16  
2
%I  
SKIP  
MAX  
I
I
= 1.2A option  
= 2.0A option  
1.6  
2.7  
2.4  
OUTB  
OUTB  
Current-Limit Threshold  
I
A
MAX  
3.4  
4.08  
                         
����������������������������������������������������������������� ꢀMaxim Integrated Productsꢀ ꢀ 3  
MAX16929  
Automotive TFT-LCD Power Supply with Boost  
Converter and Gate Voltage Regulators  
ELECTRICALꢀCHARACTERISTICSꢀ(continued)  
(V  
= 12V, V  
= 5V, V  
= V  
= 0V, T = T = -40NC to +105NC, typical values are at T = +25NC, unless otherwise noted.)  
INB  
INA  
GND  
PGNDP A J A  
(Note 2)  
PARAMETER  
SYMBOL  
CONDITIONS  
MIN  
TYP  
3.9  
80  
MAX  
UNITS  
ms  
%
Soft-Start Ramp Time  
Maximum Duty Cycle  
Minimum Duty Cycle  
Continuous mode  
Continuous mode  
Dropout  
20  
%
Maximum Duty Cycle in Dropout  
Thermal Shutdown Temperature  
Thermal Shutdown Hysteresis  
POWERꢀGOODꢀ(PGOOD)  
95  
%
+175  
15  
NC  
NC  
Rising  
Falling  
94  
92  
13  
PGOOD Threshold  
%
90  
95  
PGOOD Debounce Time  
Output High-Leakage Current  
Output Low Level  
Fs  
FA  
V
0.2  
0.4  
LOGICꢀLEVELS  
ENB Threshold  
ENB rising  
1.4  
3
1.8  
0.2  
5
2.2  
9
V
V
ENB Hysteresis  
ENB Input Current  
FA  
BOOST,ꢀPOSITIVEꢀ(GH),ꢀNEGATIVEꢀ(GL),ꢀ1.8V/3.3VꢀCONVERTERS  
INA Input Supply Range  
V
3
5.5  
2.0  
V
INA  
V
= V  
= 1.3V, V  
= 0V,  
FBP  
FBGH  
FBGL  
INA Supply Current  
I
1.5  
2.7  
mA  
INA  
LXP not switching  
V rising, hysteresis = 200mV,  
INA  
INA Undervoltage Lockout  
Threshold  
V
2.5  
2.9  
V
INA,UVLO  
T
= +25NC  
A
INA Shutdown Current  
I
V
= 0V, T = +25NC  
0.5  
+165  
15  
FA  
NC  
NC  
SHDN  
ENP  
A
Thermal Shutdown Temperature  
Thermal Shutdown Hysteresis  
T
Temperature rising  
SHDN  
T
H
V
old  
, V  
, or V  
below its thresh-  
FBP FBGH  
FBGL  
Duration to Trigger Fault Condition  
238  
1.9  
ms  
s
Autoretry Time  
REFERENCEꢀ(REF)  
REF Output Voltage  
REF Load Regulation  
V
No output current  
0 < I < 80FA, REF sourcing  
1.236  
-2  
1.25  
1.264  
+2  
V
REF  
%
REF  
REF Undervoltage Lockout  
Threshold  
Rising edge, hysteresis = 200mV  
1.165  
V
OSCILLATOR  
Internal Oscillator Frequency  
f
T
= +25NC  
A
3.96  
4.40  
4.84  
MHz  
MHz  
OSC  
Spread-Spectrum Modulation  
Frequency  
f
f
/2  
OSC  
SS  
                         
����������������������������������������������������������������� ꢀMaxim Integrated Productsꢀ ꢀ 4  
MAX16929  
Automotive TFT-LCD Power Supply with Boost  
Converter and Gate Voltage Regulators  
ELECTRICALꢀCHARACTERISTICSꢀ(continued)  
(V  
= 12V, V  
= 5V, V  
= V  
= 0V, T = T = -40NC to +105NC, typical values are at T = +25NC, unless otherwise noted.)  
INB  
INA  
GND  
PGNDP A J A  
(Note 2)  
PARAMETER  
SYMBOL  
SSR  
CONDITIONS  
As a percentage of switching frequency,  
MIN  
TYP  
MAX  
UNITS  
Spread-Spectrum Factor  
Q4  
%
f
SW  
BOOSTꢀCONVERTER  
Switching Frequency  
Maximum Duty Cycle  
f
1.98  
82  
2.20  
2.42  
93.5  
MHz  
%
SW  
Low boost current-  
limit option  
0.625  
1.25  
0.78  
1.56  
Duty cycle = 70%,  
= 220pF  
LXP Current Limit  
I
A
LIM  
C
COMPI  
High boost current-  
limit option  
1.87  
LXP On-Resistance  
LXP Leakage Current  
Soft-Start Time  
R
I
= 200mA  
110  
8.5  
30  
250  
20  
mI  
FA  
ms  
V
DS_ON(LXP) LXP  
I
V
= 20V, T =+25NC  
LK_LXP  
LXP A  
(Note 4)  
Output Voltage Range  
V
V
18  
SH  
INA  
T
= +3V to +5.5V,  
= +25NC  
0.985  
0.98  
0.74  
1.0  
1.0  
0.85  
-1  
1.015  
1.02  
0.96  
V
0 < I  
A
INA  
FBP Regulation Voltage  
V
V
FBP  
< full load  
T =-40NCto+105NC  
LOAD  
A
PGOOD Threshold  
V
Measured at FBP  
0 < I < full load  
V
%
PG_FBP  
FBP Load Regulation  
FBP Line Regulation  
FBP Input Bias Current  
LOAD  
V
V
= +3V to +5.5V  
0.1  
%/V  
FA  
FS  
INA  
= +1V, T = +25NC  
Q1  
FBP  
A
FBP to COMPV Transconductance  
POSITIVE-GATEꢀVOLTAGEꢀREGULATORꢀ(GH)  
DI = Q2.5FA at COMPV, T = +25NC  
400  
A
With external charge pump, T = +25NC  
A
Output Voltage Range  
V
5
29  
V
GH  
(maximum V = 29.5V)  
CP  
CP Overvoltage Threshold  
FBGH Regulation Voltage  
PGOOD Threshold  
T
= +25NC (Note 6)  
29.5  
0.98  
0.83  
30.5  
1.0  
0.85  
2
V
V
A
V
I
= 1mA  
1.034  
0.87  
FBGH  
GH  
V
Measured at FBGH  
V
PG_FBGH  
FBGH Load Regulation  
I
= 0 to 20mA  
%
GH  
V
= 12V to 20V at V  
= 10mA  
= 10V,  
GH  
CP  
FBGH Line Regulation  
2
%
I
GH  
FBGH Input Bias Current  
GH Output Current  
GH Current Limit  
V
V
= 1V, T = +25NC  
Q1  
FA  
mA  
mA  
ms  
FBGH  
A
I
- V = 2V  
GH  
20  
35  
GH  
CP  
I
56  
LIM_GH  
GH Soft-Start Time  
7.45  
NEGATIVE-GATEꢀVOLTAGEꢀREGULATORꢀ(GL)  
Output Voltage Range  
V
-24  
-2  
V
V
DRVN  
FBGL Regulation Voltage  
V
I
= 100FA  
0.212  
0.242  
0.271  
FBGL  
DRVN  
                         
����������������������������������������������������������������� ꢀMaxim Integrated Productsꢀ ꢀ 5  
MAX16929  
Automotive TFT-LCD Power Supply with Boost  
Converter and Gate Voltage Regulators  
ELECTRICALꢀCHARACTERISTICSꢀ(continued)  
(V  
= 12V, V  
= 5V, V  
= V  
= 0V, T = T = -40NC to +105NC, typical values are at T = +25NC, unless otherwise noted.)  
INB  
INA  
GND  
PGNDP A J A  
(Note 2)  
PARAMETER  
SYMBOL  
CONDITIONS  
Measured at FBGL  
MIN  
TYP  
MAX  
0.42  
Q1  
UNITS  
V
PGOOD Threshold  
V
0.38  
0.4  
PG_FBGL  
FBGL Input Bias Current  
DRVN Source Current  
V
= +0.25V  
FA  
FBGL  
FBGL  
V
= +0.5V, V  
= -10V  
2
mA  
mA  
ms  
DRVN  
DRVN Source Current Limit  
GL Soft-Start Time  
2.5  
4
7.45  
1.8V/3.3VꢀREGULATORꢀCONTROLLER  
3.3V regulator option  
1.8V regulator option  
3.18  
3.3  
1.8  
3.38  
Output Voltage  
V
V
= V  
FB  
V
V
FB  
DR  
1.746  
1.854  
3.3V regulator option,  
FB rising  
2.4  
2.57  
2.7  
Measured at FB  
(Notes 5, 7)  
FB PGOOD Threshold  
V
PG_FB  
1.8V regulator option  
1.364  
1.38  
2.5  
4.5  
6
1.396  
V
V
V
= 1.8V  
= 3.3V  
= 1.8V  
FB  
FB  
FB  
FB Input Bias Current  
FA  
DR Drive Current  
4.5  
33  
mA  
INPUTꢀSERIESꢀSWITCHꢀCONTROL  
p-Channel FET GATE Sink Current  
V
= 0.5V  
55  
75  
FA  
GATE  
Measured at GATE; below this voltage, the  
external p-channel FET is considered on  
GATE Voltage Threshold  
1.25  
V
DIGITALꢀLOGIC  
ENP, SEQ Input Pulldown Resistor  
Value  
R
V
500  
kI  
PD  
ENP, SEQ Input-Voltage Low  
ENP, SEQ Input-Voltage High  
PGOOD Leakage Current  
V
0.3 x V  
V
V
IL  
INA  
0.7 x V  
IH  
INA  
I
T
= +25NC  
A
Q1  
FA  
V
LK_IN  
PGOOD Output-Voltage Low  
V
2mA sink current, T = +25NC  
0.4  
OL  
A
Noteꢀ2: Specifications over temperature are guaranteed by design and not production tested.  
Noteꢀ3: Operation in light-load conditions or at extreme duty cycles result in skipped cycles, resulting in lower operating frequency  
and possibly limited output accuracy and load response.  
Noteꢀ4: 50% of the soft-start voltage time is due to the soft-start ramp, and the other 50% is due to the settling of the output voltage.  
Noteꢀ5: Guaranteed by design; not production tested.  
Noteꢀ6: After the voltage at CP exceeds this overvoltage threshold, the entire circuit switches off and autoretry is started.  
Noteꢀ7: FB power good is indicated by PGOOD. The condition V < V  
does not shutdown/restart the device.  
FB  
PG_FB  
                         
����������������������������������������������������������������� ꢀMaxim Integrated Productsꢀ ꢀ 6  
MAX16929  
Automotive TFT-LCD Power Supply with Boost  
Converter and Gate Voltage Regulators  
Typical Operating Characteristics  
(V  
= 5V, V  
= 12V, measurements taken on “A” version, unless otherwise noted; V = 12V, V  
= 18V, V = -6V, V  
= 3.3V,  
REG  
INA  
INB  
A
SH  
GH  
GL  
V
= 5V, T = +25NC, unless otherwise noted.)  
OUTB  
SHUTDOWN SUPPLY CURRENT (BUCK)  
EFFICIENCY vs. LOAD CURRENT (BUCK)  
20  
100  
90  
80  
70  
60  
50  
40  
30  
20  
10  
0
18  
16  
14  
12  
10  
8
V
=12V  
INB  
V
=18V  
INB  
V
= 28V  
INB  
6
4
2
0
4
8
12  
16  
20  
24  
28  
0
0.4  
0.8  
1.2  
1.6  
2.0  
SUPPLY VOLTAGE (V)  
LOAD CURRENT (A)  
LINE REGULATION (BUCK)  
LOAD REGULATION (BUCK)  
4.0  
3.2  
6
5
4
I
= 0A  
OUTB  
2.4  
3
1.6  
V
= 12V  
INB  
2
0.8  
I
= 1A  
OUTB  
1
0
0
-1  
-2  
-3  
-4  
-5  
-6  
V
= 18V  
INB  
-0.8  
-1.6  
-2.4  
-3.2  
-4.0  
V
= 28V  
INB  
I
= 2A  
OUTB  
4
6
8
10 12 14 16 18 20 22 24 26 28  
INPUT VOLTAGE (V)  
0
0.4  
0.8  
1.2  
1.6  
2.0  
LOAD CURRENT (A)  
STARTUP WAVEFORMS (BUCK)  
LOAD-TRANSIENT RESPONSE (BUCK)  
MAX16929 toc06  
MAX16929 toc05  
V
ENB  
1.8A  
0.2A  
5V/div  
I
OUTB  
1A/div  
I
LXB  
2A/div  
V
OUTB  
V
OUTB  
2V/div  
(AC-COUPLED)  
100mV/div  
1ms/div  
400µs/div  
                         
����������������������������������������������������������������� ꢀMaxim Integrated Productsꢀ ꢀ 7  
MAX16929  
Automotive TFT-LCD Power Supply with Boost  
Converter and Gate Voltage Regulators  
Typical Operating Characteristics (continued)  
(V  
= 5V, V  
= 12V, measurements taken on “A” version, unless otherwise noted; V = 12V, V  
= 18V, V = -6V, V = 3.3V,  
REG  
INA  
INB  
A
SH  
GH  
GL  
V
= 5V, T = +25NC, unless otherwise noted.)  
OUTB  
LINE-TRANSIENT RESPONSE (BUCK)  
SHORT-CIRCUIT BEHAVIOR (BUCK)  
MAX16929 toc08  
MAX16929 toc07  
V
OUTB  
28V  
12V  
5V/div  
V
INB  
10V/div  
I
LXB  
2A/div  
V
OUTB  
V
PGOOD  
(AC-COUPLED)  
50mV/div  
5V/div  
1ms/div  
100ms/div  
LOAD DUMP RESPONSE  
INA SHUTDOWN SUPPLY CURRENT  
MAX16929 toc09  
10  
9
8
7
6
5
4
3
2
1
0
42V  
12V  
V
INB  
20V/div  
I
LXB  
2A/div  
V
OUTB  
5V/div  
100ms/div  
3.0  
3.5  
4.0  
4.5  
5.0  
5.5  
INPUT VOLTAGE (V)  
EFFICIENCY vs. LOAD CURRENT  
(BOOST)  
LOAD REGULATION (BOOST)  
LINE REGULATION (BOOST)  
100  
90  
80  
70  
60  
50  
40  
30  
20  
10  
0
1.0  
1.0  
0.8  
I
= 0mA  
LOAD  
0.8  
0.6  
0.6  
V
= 5V  
INA  
0.4  
0.2  
0.4  
V
= 3.3V  
INA  
0.2  
V
= 3.3V  
INA  
0
0
-0.2  
-0.4  
-0.6  
-0.8  
-1.0  
-0.2  
-0.4  
-0.6  
-0.8  
-1.0  
V
= 5V  
INA  
0
100  
200  
300  
400  
500  
0
100  
200  
300  
400  
500  
3.0  
3.5  
4.0  
4.5  
5.0  
5.5  
LOAD CURRENT (mA)  
LOAD CURRENT (mA)  
INPUT VOLTAGE (V)  
                         
����������������������������������������������������������������� ꢀMaxim Integrated Productsꢀ ꢀ 8  
MAX16929  
Automotive TFT-LCD Power Supply with Boost  
Converter and Gate Voltage Regulators  
Typical Operating Characteristics (continued)  
(V  
= 5V, V  
= 12V, measurements taken on “A” version, unless otherwise noted; V = 12V, V  
= 18V, V = -6V, V  
= 3.3V,  
REG  
INA  
INB  
A
SH  
GH  
GL  
V
= 5V, T = +25NC, unless otherwise noted.)  
OUTB  
STARTUP WAVEFORMS (BOOST)  
LOAD-TRANSIENT RESPONSE (BOOST)  
MAX16929 toc14  
MAX16929 toc15  
V
ENP  
5V/div  
450mA  
50mA  
V
LXP  
I
SH  
10V/div  
500mA/div  
I
LXP  
1A/div  
V
SH  
100mV/div  
V
SH  
10V/div  
4ms/div  
100µs/div  
SUPPLY SEQUENCING WAVEFORMS  
SUPPLY SEQUENCING WAVEFORMS  
(V  
SEQ  
= 0V)  
(V  
SEQ  
= V  
)
INA  
MAX16929 toc16  
MAX16929 toc17  
V
V
ENP  
ENP  
5V/div  
5V/div  
V
V
GH  
GH  
5V/div  
5V/div  
V
V
SH  
SH  
5V/div  
5V/div  
V
REG  
V
REG  
5V/div  
5V/div  
V
V
GL  
GL  
5V/div  
5V/div  
10ms/div  
10ms/div  
LOAD REGULATION (GH REGULATOR)  
LINE REGULATION (GH REGULATOR)  
0
-0.4  
-0.8  
-1.2  
-1.6  
-2.0  
-2.4  
-2.6  
-3.2  
-3.6  
-4.0  
1.0  
0.8  
0.6  
0.4  
I
= 10mA  
LOAD  
0.2  
0
-0.2  
-0.4  
-0.6  
-0.8  
-1.0  
I
= 20mA  
LOAD  
0
2
4
6
8
10 12 14 16 18 20  
18 19 20 21 22 23 24 25 26 27 28 29 30  
VOLTAGE (V)  
LOAD CURRENT (mA)  
V
CP  
                         
����������������������������������������������������������������� ꢀMaxim Integrated Productsꢀ ꢀ 9  
MAX16929  
Automotive TFT-LCD Power Supply with Boost  
Converter and Gate Voltage Regulators  
Typical Operating Characteristics (continued)  
(V  
= 5V, V  
= 12V, measurements taken on “A” version, unless otherwise noted; V = 12V, V  
= 18V, V = -6V, V  
= 3.3V,  
REG  
INA  
INB  
A
SH  
GH  
GL  
V
= 5V, T = +25NC, unless otherwise noted.)  
OUTB  
LINE REGULATION  
(GL REGULATOR)  
LOAD REGULATION  
(GL REGULATOR)  
1.0  
0.8  
3.0  
2.7  
2.4  
2.1  
1.8  
1.5  
1.2  
0.9  
0.6  
0.3  
0
0.6  
0.4  
0.2  
I
= 20mA  
= 10mA  
LOAD  
0
-0.2  
-0.4  
-0.6  
-0.8  
-1.0  
I
LOAD  
-24 -22 -20 -18 -16 -14 -12 -10 -8 -6  
VOLTAGE (V)  
0
2
4
6
8
10 12 14 16 18 20  
V
LOAD CURRENT (mA)  
CN  
LOAD REGULATION  
(3.3V LINEAR REGULATOR)  
LOAD-TRANSIENT RESPONSE  
(3.3V LINEAR REGULATOR)  
MAX16929 toc23  
0
-0.02  
-0.04  
-0.06  
-0.08  
-0.10  
-0.12  
-0.14  
-0.16  
-0.18  
-0.20  
450mA  
50mA  
I
OUTB  
500mA/div  
V
REG  
(AC-COUPLED)  
100mV/div  
0
50 100 150 200 250 300 350 400 450 500  
LOAD CURRENT (mA)  
100µs/div  
                         
���������������������������������������������������������������� ꢀMaxim Integrated Productsꢀ ꢀ 10  
MAX16929  
Automotive TFT-LCD Power Supply with Boost  
Converter and Gate Voltage Regulators  
Pin Configuration  
TOP VIEW  
1
2
28  
27  
26  
25  
24  
23  
22  
21  
20  
19  
18  
17  
16  
15  
ENP  
DR  
SEQ  
REF  
3
FB  
FBGL  
FBGH  
COMPI  
GND  
DRVN  
GH  
4
GATE  
PGNDP  
LXP  
5
MAX16929  
6
7
INA  
8
COMPV  
FBP  
9
CP  
10  
11  
12  
13  
14  
FBB  
PGOOD  
GND  
ENB  
AVL  
BST  
LXB  
INB  
EP  
LXB  
INB  
TSSOP  
Pin Description  
PIN  
NAME  
FUNCTION  
Boost Circuitry and 1.8V/3.3V Regulator Controller Enable Input. ENP has an internal 500kI pulldown  
resistor. Drive high for normal operation and drive low to place the device (except buck converter) in  
shutdown.  
1
ENP  
1.8V or 3.3V Regulator Output. DR has a 4.5mA (min) drive capability. For greater output current capa-  
bility, use an external npn bipolar transistor whose base is connected to DR.  
2
3
DR  
FB  
1.8V or 3.3V Regulator Feedback Input. FB is regulated to 1.8V or 3.3V. Connect FB to DR when power-  
ing loads demanding less than 4.5mA. For greater output current capability, use an external npn bipo-  
lar transistor whose emitter is connected to FB.  
External p-Channel FET Gate Drive. GATE is an open-drain driver connected to the gate of the external  
input series p-channel FET. Connect a pullup resistor between GATE and INA. During a fault condition,  
the gate driver turns off and the pullup resistor turns off the FET.  
4
GATE  
5
6
7
PGNDP  
LXP  
Boost Converter Power Ground  
Boost Converter Switching Node. Connect LXP to the inductor and catch diode of the boost converter.  
Boost Circuitry and 1.8V/3.3V Regulator Controller Power Input. Connect INA to a 3V to 5.5V supply.  
INA  
Boost Error Amplifier Compensation Connection. Connect a compensation network between COMPV to  
GND.  
8
9
COMPV  
FBP  
Boost Converter Feedback Input. FBP is regulated to 1V. Connect FBP to the center of a resistive divid-  
er connected between the boost output and GND.  
                         
���������������������������������������������������������������� ꢀMaxim Integrated Productsꢀ ꢀ 11  
MAX16929  
Automotive TFT-LCD Power Supply with Boost  
Converter and Gate Voltage Regulators  
Pin Description (continued)  
PIN  
NAME  
FUNCTION  
Buck Converter Feedback Input. FBB is regulated to either 3.3V or 5V. Connect FBB to the output-volt-  
age node, OUTB, as shown in the Typical Application Circuit.  
10  
FBB  
Buck Converter Internal 5V Regulator. Connect a 1FF capacitor between AVL and the analog ground  
plane. Do not use AVL to power external circuitry.  
11  
12  
AVL  
BST  
LXB  
Buck Converter Bootstrap Capacitor Connection. Connect a 0.1FF capacitor between BST and LXB.  
Buck Converter Inductor Connection. Connect the inductor, boost capacitor, and catch diode at this  
node.  
13, 14  
Buck Converter Power Input. Connect to a 4V to 28V supply. Connect a 1FF or larger ceramic capaci-  
tor in parallel with a 47FF bulk capacitor from INB to the power ground plane. Connect both INB power  
inputs together.  
15, 16  
INB  
Buck Converter Enable Input. ENB is a high-voltage compatible input. Connect to INB for normal opera-  
tion and connect to ground to disable the buck converter.  
17  
ENB  
18, 23  
19  
GND  
Analog Ground  
PGOOD Open-Drain Power-Good Output. Connect PGOOD to INA through an external pullup resistor.  
Positive-Gate Voltage Regulator Power Input. Connect CP to the positive output of the external charge  
20  
CP  
pump. Ensure that V does not exceed the CP overvoltage threshold as given in the Electrical  
CP  
Characteristics table.  
21  
22  
GH  
Positive-Gate Voltage Regulator Output  
Negative-Gate Voltage Regulator Driver Output. DRVN is the open drain of an internal p-channel FET.  
Connect DRVN to the base of an external npn pass transistor.  
DRVN  
Boost Slope Compensation Connection. Connect a capacitor between COMPI and GND to set the  
slope compensation.  
24  
25  
COMPI  
FBGH  
Positive-Gate Voltage Regulator Feedback Input. FBGH is regulated to 1V. Connect FBGH to the center  
of a resistive divider connected between GH and GND.  
Negative-Gate Voltage Regulator Feedback Input. FBGL is regulated to 0.25V. Connect FBGL to the  
center of a resistive divider connected between REF and the output of the negative-gate voltage  
regulator.  
26  
FBGL  
27  
28  
REF  
SEQ  
1.25V Reference Output. Bypass REF to GND with a 0.1FF ceramic capacitor.  
Sequencing Input. SEQ has an internal 500kI pulldown resistor. SEQ determines the sequence in  
which V  
and V power-up. See Table 1 for supply sequencing options.  
GH  
GL  
Exposed Pad. Connect to a large contiguous copper ground plane for optimal heat dissipation. Do not  
use EP as the only electrical ground connection.  
EP  
                         
���������������������������������������������������������������� ꢀMaxim Integrated Productsꢀ ꢀ 12  
MAX16929  
Automotive TFT-LCD Power Supply with Boost  
Converter and Gate Voltage Regulators  
enabling the buck converter, V  
begins to rise. Once  
AVL  
Detailed Description  
V
exceeds the undervoltage lockout voltage of 3.5V  
AVL  
(max), LXB starts switching. Bypass AVL to GND with a  
The MAX16929 is a highly integrated power supply for  
automotive TFT-LCD applications. The device integrates  
one buck converter, one boost converter, one 1.8V/3.3V  
regulator controller, one positive-gate voltage regulator,  
and one negative-gate voltage regulator.  
1FF ceramic capacitor.  
Spread-Spectrum Modulation  
The buck converter features spread-spectrum operation  
that varies the internal operating frequency of the buck  
converter by +6% relative to the switching frequency of  
2.1MHz (typ).  
The device achieves enhanced EMI performance through  
spread-spectrum modulation. Digital input control allows  
the device to be placed in a low-current shutdown mode  
and provides flexible sequencing of the gate voltage  
regulators.  
Soft-Start  
The buck converter features an internal soft-start timer.  
The output voltage takes 3.9ms to ramp up to its set  
voltage. If a short circuit or undervoltage is encountered  
after the soft-start timer has expired, the device enters  
hiccup mode, during which soft-start is reattempted  
every 16ms. This process repeats until the short circuit  
has been removed.  
Internal thermal shutdown circuitry protects the device  
from overheating. The buck converter is designed to  
shut down when its die temperature reaches +175NC  
(typ), while the boost circuitry does so at +165NC (typ).  
Each resumes normal operation once its die temperature  
has fallen 15NC below its respective thermal shutdown  
temperature.  
Overcurrent Protection  
The device enters hiccup mode in one of three ways. If  
eight consecutive current limits are detected and the out-  
put is below 77% of its nominal value, the buck converter  
enters hiccup mode. The converter enters hiccup mode  
immediately if the output is short circuited to ground  
(output below 1V). Additionally, the device enters hiccup  
mode if 256 consecutive overcurrent events are detected  
when the output is greater than 77% of its nominal value.  
In hiccup mode, the buck controller idles for 16ms before  
reattempting soft-start.  
The device is factory-trimmed to provide a variety of  
power options to meet the most common automotive  
TFT-LCD display power requirements, as outlined in the  
Ordering Information/Selector Guide table.  
Buck Converter  
The device features a current-mode buck converter with  
an integrated high-side FET, which requires no external  
compensation network. The buck converter regulates the  
output voltage to within Q3% in continuous mode over  
line and load conditions. The high 2.1MHz (typ) switching  
frequency allows for small external components, reduced  
output ripple, and guarantees no AM interference.  
Power Good (PGOOD)  
When an overcurrent condition causes the buck output to  
fall below 92% of its set voltage, the open-drain power-  
good indicator output (PGOOD) asserts low. PGOOD  
deasserts once the output voltage has risen above 95%  
of its set voltage.  
A power-good (PGOOD) indicator is available to moni-  
tor output-voltage quality. The enable input allows the  
device to be placed in shutdown, reducing supply cur-  
rent to 70FA.  
PGOOD serves as a general fault indicator for all the  
converters and regulators. Besides indicating an under-  
voltage on the buck output, it also indicates any of the  
faults listed in the Fault Conditions and PGOOD section.  
The buck converter comes with a preset output voltage  
of either 3.3V or 5V, and can deliver either 1.2A or 2A to  
the output.  
Enable (ENB)  
Connect ENB to INB for always-on operation. ENB is also  
compatible with 3.3V logic systems and can be con-  
trolled through a microcontroller or by automotive KEY or  
CAN inhibit signals.  
Boost Converter  
The boost converter employs a current-mode, fixed-  
frequency PWM architecture to maximize loop bandwidth  
and provide fast transient response to pulsed loads typical  
of TFT-LCD panel source drivers. The 2.2MHz switching  
frequency allows the use of low-profile inductors and  
ceramic capacitors to minimize the thickness of LCD panel  
designs. The integrated low on-resistance MOSFET and  
Internal 5V Regulator (AVL)  
AVL is an internal 5V regulator that supplies power to the  
buck controller and charges the boost capacitor. After  
                         
���������������������������������������������������������������� ꢀMaxim Integrated Productsꢀ ꢀ 13  
MAX16929  
Automotive TFT-LCD Power Supply with Boost  
Converter and Gate Voltage Regulators  
the device’s built-in digital soft-start functions reduce the  
number of external components required while control-  
ling inrush currents. The output voltage can be set from  
to 1V and changes the COMPV output. The voltage at  
COMPV sets the peak inductor current. As the load var-  
ies, the error amplifier sources or sinks current to the  
COMPV output accordingly to produce the peak induc-  
tor current necessary to service the load. To maintain  
stability at high duty cycles, a slope-compensation sig-  
nal (set by the capacitor at COMPI) is summed with the  
current-sense signal. On the rising edge of the internal  
clock, the controller turns on the n-channel MOSFET and  
applies the input voltage across the inductor. The current  
through the inductor ramps up linearly, storing energy in  
its magnetic field. Once the sum of the current feedback  
signal and the slope compensation exceeds the COMPV  
voltage, the controller turns off the MOSFET. The inductor  
current then flows through the diode to the output. The  
MOSFET remains off for the rest of the clock cycle.  
V
INA  
to 18V with an external resistive voltage-divider.  
The regulator controls the output voltage by modulat-  
ing the duty cycle (D) of the internal power MOSFET in  
each switching cycle. The duty cycle of the MOSFET is  
approximated by:  
ηV  
IN  
D=1−  
V
O
where V is the voltage at INA, V = V (the boost  
SH  
IN  
O
output voltage), and E is the efficiency of the boost con-  
verter, as shown in the Typical Operating Characteristics.  
Figure 1 shows the functional diagram of the boost  
regulator. An error amplifier compares the signal at FBP  
LXP  
CLOCK  
LOGIC AND  
DRIVER  
PGNDP  
I
LIM  
COMPARATOR  
SOFT-  
START  
V
LIMIT  
PWM  
COMPARATOR  
CURRENT  
SENSE  
Σ
2.2MHz  
OSCILLATOR  
SLOPE  
COMP  
COMPI  
FBP  
ERROR  
AMP  
TO FAULT LOGIC  
0.85V  
FAULT  
COMPARATOR  
1V  
MAX16929  
COMPV  
Figure 1. Boost Converter Functional Diagram  
                         
���������������������������������������������������������������� ꢀMaxim Integrated Productsꢀ ꢀ 14  
MAX16929  
Automotive TFT-LCD Power Supply with Boost  
Converter and Gate Voltage Regulators  
The external p-channel FET controlled by GATE protects  
the output during fault conditions and provides True  
Shutdown of the converter. Connect a pullup resistor  
between GATE and INA (see the Boost Converter section  
to select the value for the pullup resistor). Under normal  
operation, GATE turns on the p-channel FET, connecting  
the supply to the boost input. During a fault condition or  
in shutdown, GATE is off and the pullup resistor turns off  
the p-channel FET, disconnecting the supply from the  
boost input.  
4) The LXP voltage is greater than 21V (typ).  
5) The positive charge-pump voltage (V ) is greater  
CP  
than 30.5V (typ).  
6) The 1.8V/3.3V regulator output voltage falls below  
85% of its nominal value.  
7) The buck output voltage falls below 92% of its nominal  
value.  
If any of the first three fault conditions persists for longer  
than the 238ms fault blanking period, the device pulls  
PGOOD low, turns off all outputs, and starts the autoretry  
timer.  
Spread-Spectrum Modulation  
The high-frequency 2.2MHz operation of the boost con-  
verter keeps switching noise outside of the AM band. The  
device achieves enhanced EMI performance by modu-  
lating the switching frequency by Q4%. The modulating  
signal is pseudorandom and changes each switching  
If either condition 4 or 5 occurs, the device pulls PGOOD  
low and turns off all outputs immediately. The device initi-  
ates startup only after the fault has cleared.  
If condition 6 occurs, the device pulls PGOOD low, but  
does not turn off any of the outputs.  
period (i.e., f = 2.2MHz).  
SS  
Startup  
During startup, PGOOD is masked and goes high as  
soon as the 1.8V/3.3V regulator controller turns on. This  
Immediately after power-up, coming out of shutdown,  
or going into autoretry, the boost converter performs a  
short-circuit detection test on the output by connecting  
the input (INA) to the switching node (LXP) through an  
internal 50I resistor.  
regulator turns on as soon as V  
undervoltage lockout threshold.  
exceeds the INA  
INA  
Autoretry  
When the autoretry counter finishes incrementing after  
1.9s, the device attempts to turn on the boost converter  
and gate voltage regulators in the order shown in  
Table 1. The device continues to autoretry as long as the  
fault condition persists. A fault on the 1.8V/3.3V regulator  
output causes PGOOD to go low, but does not result in  
the device shutting down and going into autoretry.  
If the resulting voltage on LXP exceeds 1.2V, the device  
turns on the external pMOS switch by pulling GATE low.  
The boost output ramps to its final value in 15ms.  
An overloaded or shorted output is detected if the result-  
ing voltage on LXP is below 1.2V. The external pMOS  
switch remains off and the converter does not switch.  
After the fault blanking period of 238ms, the device pulls  
PGOOD low and starts the autoretry timer.  
Current Limit  
The effective current limit of the boost converter is  
reduced by the internally injected slope compensation by  
an amount dependent on the duty cycle of the converter.  
The effective current limit is given by:  
The short-circuit detection feature places a lower limit  
on the output load of approximately 46I when the input  
voltage is 3V.  
Fault Conditions and PGOOD  
PGOOD signals whether all the regulators and the boost  
converter are operating normally. PGOOD is an open-  
drain output that pulls low if any of the following faults  
occur:  
D
-12  
I
=192 ×10  
×I  
×
LIM(EFF)  
LIM_DC_0  
C
COMPI  
where I  
is the effective current limit, I  
=
LIM(EFF)  
LIM_DC_0  
1.1A or 2.2A depending on the boost converter current-  
limit option, D is the duty cycle of the boost converter,  
1) The boost output voltage falls below 85% of its set  
value.  
and C  
is the value of the capacitor at the COMPI  
input. Estimate the duty cycle of the converter using the  
formulas shown in the Design Procedure section.  
COMPI  
2) The positive-gate voltage regulator output (V ) falls  
GH  
below 85% of its set value.  
3) The negative-gate voltage regulator output (V ) falls  
GL  
below 85% of its set value.  
                         
���������������������������������������������������������������� ꢀMaxim Integrated Productsꢀ ꢀ 15  
MAX16929  
Automotive TFT-LCD Power Supply with Boost  
Converter and Gate Voltage Regulators  
dependent bypassing requirements. Connect a ceramic  
capacitor between the collector and ground with the  
value shown in Table 3.  
1.8V/3.3V Regulator Controller  
The 1.8V/3.3V regulator controller delivers 4.5mA (min)  
to an external load. Connect FB to DR for a regulated  
1.8V/3.3V output.  
The regulator derives its negative supply voltage from an  
inverting charge pump, a single-stage example of which  
is shown in the Typical Application Circuit. A more nega-  
tive voltage using a multistage charge pump is possible  
as described in the Charge Pumps section.  
For higher output capability, use an external npn transis-  
tor as shown in the Typical Application Circuit. The drive  
capability of the regulator is then increased by the cur-  
rent gain of the transistor (h ). When using an external  
FE  
transistor, use DR as the base drive and connect FB to  
the transistor’s emitter. Bypass the base to ground with a  
0.1FF ceramic capacitor.  
The external npn transistor is not short-circuit protected.  
To maintain proper pulldown capability of external npn  
transistor and optimal regulation, a minimum load of at  
least 500µA is recommended on the output of the GL  
regulator.  
If the boost output current is greater than 300mA, con-  
nect a 30kI resistor between DR and GND.  
Enable (ENP)  
Use the enable input (ENP) to enable and disable the  
boost section of the device. Connect ENP to INA for  
normal operation and to GND to place the device in shut-  
down. In shutdown, the INA supply current is reduced to  
0.5FA.  
Positive-Gate Voltage Regulator (GH)  
The positive-gate voltage regulator includes a p-channel  
FET output stage to generate a regulated output between  
+5V and V - 2V. The regulator maintains accuracy over  
CP  
wide line and load conditions. It is capable of at least  
20mA of output current and includes current-limit protec-  
tion. V  
drivers’ gate-on voltage.  
is typically used to provide the TFT-LCD gate  
GH  
Soft-Start and Supply Sequencing (SEQ)  
When enabled, the boost output ramps up from V  
to  
INA  
The regulator derives its positive supply voltage from a  
noninverting charge pump, a single-stage example of  
which is shown in the Typical Application Circuit. A high-  
er voltage using a multistage charge pump is possible,  
as described in the Charge Pumps section.  
its set voltage. Once the boost output reaches 85% of the  
set voltage and the soft-start timer expires, the gate volt-  
age regulators turn on in the order shown in Table 1. The  
1.8V/3.3V regulator controller is enabled at the beginning  
of the boost converter’s soft-start.  
Both gate voltage regulators have a 7.45ms soft-start  
time. The second one turns on as soon as the output of  
the first reaches 85% of its set voltage.  
Negative-Gate Voltage Regulator (GL)  
The negative-gate voltage regulator is an analog gain  
block with an open-drain p-channel output. It drives an  
external npn pass transistor with a 6.8kI base-to-emitter  
resistor (see the Pass Transistor Selection section). Its  
guaranteed base drive source current is at least 2mA.  
Thermal Shutdown  
Internal thermal shutdown circuitry shuts down the  
device immediately when the die temperature exceeds  
+165NC. A 15NC thermal shutdown hysteresis prevents  
the device from resuming normal operation until the die  
temperature falls below +150NC.  
V
is typically used to provide the TFT-LCD gate driv-  
GL  
ers’ gate-off voltage.  
The output of the negative-gate voltage regulator (i.e.,  
the collector of the external npn pass transistor) has load-  
Tableꢀ1.ꢀSupplyꢀSequencing  
CONTROLꢀINPUTS  
SUPPLYꢀSEQUENCING  
ENP  
SEQ  
FIRST  
SECOND  
THIRD  
0
1
1
X
0
1
Device is in shutdown  
V
V
V
V
GL  
SH  
GH  
V
V
GH  
SH  
GL  
                         
���������������������������������������������������������������� ꢀMaxim Integrated Productsꢀ ꢀ 16  
MAX16929  
Automotive TFT-LCD Power Supply with Boost  
Converter and Gate Voltage Regulators  
Tableꢀ2.ꢀMinimumꢀBuckꢀInductorꢀValueꢀ  
RequiredꢀforꢀNormalꢀOperationꢀDuringꢀ  
LoadꢀDump  
Design Procedure  
Buck Converter  
Inductor Selection  
Three key inductor parameters must be specified for  
operation with the device: inductance value (L), induc-  
BUCKꢀV  
(V)  
BUCKꢀI  
(A)  
L
(µH)  
MINꢀ  
OUTBꢀ  
OUTBꢀ  
3.3  
1.2  
3.3  
tor saturation current (I  
), and DC resistance (R ).  
SAT  
DC  
3.3  
5
2
6.8  
3.3  
4.7  
To determine the inductance value, select the ratio of  
inductor peak-to-peak ripple current to average output  
current (LIR) first. For LIR values that are too high, the  
RMS currents are high, and therefore I2R losses are high.  
Use high-valued inductors to achieve low LIR values.  
Typically, inductance is proportional to resistance for a  
given package type, which again makes I2R losses high  
for very low LIR values. A good compromise between  
size and loss is to select a 30%-to-60% peak-to-peak  
ripple current to average-current ratio. If extremely thin  
high-resistance inductors are used, as is common for  
LCD-panel applications, the best LIR can increase  
between 0.5 and 1.0. The size of the inductor is deter-  
mined as follows:  
1.2  
2
5
Capacitor Selection  
The input and output filter capacitors should be of a low-  
ESR type (tantalum, ceramic, or low-ESR electrolytic) and  
should have I  
ratings greater than:  
RMS  
2
LIR  
12  
I
= I D× (1-D +  
)
for the input capacitor  
INB(RMS)  
O
LIR×I  
O
I
=
for the output capacitor  
OUTB(RMS)  
12  
where D is the duty cycle given above.  
(V  
-V )×D  
O
INB  
L =  
and  
The output voltage contains a ripple component whose  
peak-to-peak value depends on the value of the ESR  
and capacitance of the output capacitor, and is approxi-  
mately given by:  
LIR×I × f  
O
SWB  
V
O
D =  
η× V  
INB  
DV  
= DV  
+ DV  
RIPPLE  
ESR CAP  
where V  
is the input voltage, V is the output volt-  
O
INB  
DV  
= LIR x I x R  
O ESR  
ESR  
age, I is the output current, E is the efficiency of the  
O
LIR×I  
O
buck converter, D is the duty cycle, and f  
is 2.1MHz  
SWB  
V  
=
CAP  
8 × C× f  
(the switching frequency of the buck converter). The  
efficiency of the buck converter can be estimated from  
the Typical Operating Characteristics and accounts for  
SWB  
Diode Selection  
The catch diode should be a Schottky type to minimize  
its voltage drop and maximize efficiency. The diode must  
be capable of withstanding a reverse voltage of at least  
the maximum input voltage in the application. The diode  
should have an average forward current rating greater  
than:  
losses in the internal switch, catch diode, inductor R  
and capacitor ESR.  
,
DC  
To ensure the buck converter does not shut down  
during load dump input-voltage transients to 42V, an  
inductor value larger than calculated above should be  
used. Table 2 lists the minimum inductance that should  
be used for proper operation during load dump. The  
I
= I × (1-D)  
O
D
saturation current rating (I  
) must be high enough to  
where D is the duty cycle given above. In addition, ensure  
that the peak current rating of the diode is greater than:  
SAT  
ensure that saturation can occur only above the maxi-  
mum current-limit value. Find a low-loss inductor having  
the lowest possible DC resistance that fits in the allotted  
dimensions.  
LIR  
2
I
× 1+  
OUTB  
                         
���������������������������������������������������������������� ꢀMaxim Integrated Productsꢀ ꢀ 17  
MAX16929  
Automotive TFT-LCD Power Supply with Boost  
Converter and Gate Voltage Regulators  
The output voltage contains a ripple component whose  
peak-to-peak value depends on the value of the ESR and  
capacitance of the output capacitor and is approximately  
given by:  
Boost Converter  
Inductor Selection  
Three key inductor parameters must be specified for  
operation with the device: inductance value (L), induc-  
tor saturation current (I  
), and DC resistance (R ).  
DV  
= DV + DV  
ESR CAP  
SAT  
DC  
RIPPLE  
To determine the inductance value, select the ratio of  
inductor peak-to-peak ripple current to average input  
current (LIR) first. For LIR values that are too high, the  
RMS currents are high, and therefore I2R losses are high.  
Use high-valued inductors to achieve low LIR values.  
Typically, inductance is proportional to resistance for a  
given package type, which again makes I2R losses high  
for very low LIR values. A good compromise between  
size and loss is to select a 30%-to-60% peak-to-peak  
ripple current to average-current ratio. If extremely thin  
high-resistance inductors are used, as is common for  
LCD-panel applications, the best LIR can increase  
between 0.5 and 1.0. The size of the inductor is deter-  
mined as follows:  
LIR  
2
V  
=I  
× (1+  
)×R  
ESR  
ESR INP  
I
×D  
O
V  
=
CAP  
C
×f  
OUT SW  
where I  
given above.  
and D are the input current and duty cycle  
INP  
Rectifier Diode  
The catch diode should be a Schottky type to minimize  
its voltage drop and maximize efficiency. The diode must  
be capable of withstanding a reverse voltage of at least  
V
SH  
. The diode should have an average forward current  
rating greater than:  
V
×D  
V ×I  
O O  
INA  
L =  
and I  
=
I
= I  
× (1-D)  
D
INP  
INP  
LIR×I  
× f  
ηV  
INP SW  
INA  
where I  
and D are the input current and duty cycle  
INP  
given above. In addition ensure that the peak current rat-  
ing of the diode is greater than:  
ηV  
V
INA  
D=1−  
O
LIR  
2
I
× 1+  
INP  
where V  
is the input voltage, V is the output voltage,  
O
INA  
I
is the output current, I  
is the average boost input  
O
INP  
current, E is the efficiency of the boost converter, D is the  
duty cycle, and f is 2.2MHz (the switching frequency  
of the boost converter). The efficiency of the boost  
converter can be estimated from the Typical Operating  
Characteristics and accounts for losses in the internal  
Output-Voltage Selection  
The output voltage of the boost converter can be adjust-  
ed by using a resistive voltage-divider formed by R  
SW  
TOP  
and R  
FBP and connect R  
Select R  
. Connect R  
between the output and  
between FBP and GND.  
BOTTOM  
TOP  
BOTTOM  
switch, catch diode, inductor R , and capacitor ESR.  
DC  
in the 10kI to 50kI range. Calculate  
BOTTOM  
R
with the following equation:  
TOP  
Capacitor Selection  
The input and output filter capacitors should be of a low-  
ESR type (tantalum, ceramic, or low-ESR electrolytic) and  
V
O
R
=R  
× (  
BOTTOM  
1)  
TOP  
V
FBP  
should have I  
ratings greater than:  
RMS  
where V  
, the boost converter’s feedback set point, is  
FBP  
LIR×I  
INP  
1V. Place both resistors as close as possible to the device  
and connect R to the analog ground plane.  
I
=
for the input capacitor  
RMS  
12  
BOTTOM  
Loop Compensation  
to set the high-frequency integrator  
COMPV  
2
LIR  
Choose R  
D+  
12  
gain for fast transient response. Choose C  
to set  
I
=I  
O
COMPV  
for the output capacitor  
RMS  
1D  
the integrator zero to maintain loop stability. For low-ESR  
output capacitors, use Table 3 to select the initial values  
where I  
given above.  
and D are the input current and duty cycle  
INP  
for R  
lel with R  
and C  
. Use a 22pF capacitor in paral-  
COMPV  
COMPV  
+ C  
.
COMPV  
COMPV  
                         
���������������������������������������������������������������� ꢀMaxim Integrated Productsꢀ ꢀ 18  
MAX16929  
Automotive TFT-LCD Power Supply with Boost  
Converter and Gate Voltage Regulators  
55FA and the resulting gate source voltage (V ) turns  
on the FET. When the gate drive is removed under a fault  
GS  
Tableꢀ3.ꢀCompensationꢀComponentꢀValues  
V
(V)  
8
18  
200  
5
SHꢀ  
condition or in shutdown, R  
bleeds off charge to turn  
SG  
off the FET. Size R  
on the FET.  
to produce the V  
needed to turn  
I
(mA)  
200  
3.3  
1.75  
5
SG  
GS  
SHꢀ  
V
(V)  
INAꢀ  
P
(W)  
3.75  
5
1.8V/3.3V Regulator Controller  
INꢀ  
npn Bipolar Transistor Selection  
Lꢀ(µH)  
ꢀ(kI)  
There are two important considerations in selecting the  
pass npn bipolar transistor: current gain (h ) and power  
R
33  
39  
COMPV  
FE  
C
ꢀ(pF)  
220  
820  
180  
330  
COMPV  
dissipation. Select a transistor with an h high enough to  
FE  
C
ꢀ(pF)  
COMPI  
ensure adequate drive capability. This condition is satis-  
fied when I  
x (h + 1) is greater than the maximum  
DR  
FE  
load current. The regulator can source I = 4.5mA (min).  
The transistor should be capable of dissipating:  
DR  
V
SH  
V
CP  
P
= (V  
- V  
) × I  
NPN_REG  
INA  
REG_OUT LOAD(MAX)  
where V  
= 1.8V or 3.3V. Bypass DR to ground  
REG_OUT  
LXP  
with a 0.1FF ceramic capacitor. For applications in which  
the boost output current exceeds 300mA, connect a  
30kI resistor from DR to ground.  
Supply Considerations  
INA needs to be at least 4.5V for the 3.3V regulator to  
operate properly.  
Figure 2. Multistage Charge Pump for Positive Output Voltage  
V
CN  
Charge Pumps  
Selecting the Number of Charge-Pump Stages  
For most applications, a single charge-pump stage is  
sufficient, as shown in the Typical Application Circuit.  
Connect the flying capacitors to LXP. The output voltages  
generated on the storage capacitors are given by:  
LXP  
V
= 2 x V + V  
- 2 x V  
CP  
SH  
SCHOTTKY D  
Figure 3. Multistage Charge Pump for Negative Output Voltage  
V
= -(V + V  
- 2 x V )  
CN  
SH  
SCHOTTKY D  
where V is the positive supply for the positive-gate volt-  
To further optimize transient response, vary R  
COMPV  
CP  
age regulator, and V  
is the negative supply for the neg-  
in 20% steps and C  
in 50% steps while observ-  
CN  
COMPV  
ative-gate voltage regulator. Where larger output voltages  
are needed, use multistage charge pumps (however, the  
maximum charge-pump voltage is limited by the absolute  
maximum ratings of CP and DRVN). Figure 2 and Figure 3  
show the configuration of a multistage charge pump for  
both positive and negative output voltages.  
ing transient-response waveforms. The ideal transient  
response is achieved when the output settles quickly with  
little or no overshoot. Connect the compensation network  
to the analog ground plane.  
Use the following formula to calculate the value for C  
-6  
:
COMPI  
C
≤ 950 × 10 × L/(V + V  
- V  
)
COMPI  
SH  
SCHOTTKY  
INA  
For mutistage charge pumps the output voltages are:  
p-Channel FET Selection  
The p-channel FET used to gate the boost converter’s  
input should have low on-resistance. Connect a resistor  
V
CP  
V
= V + n × (V + V  
- 2 x V )  
SH  
SH  
SCHOTTKY D  
= -n × (V + V  
- 2 x V )  
D
CN  
SH  
SCHOTTKY  
(R ) between the source and gate of the FET. Under  
For highest efficiency, choose the lowest number of  
charge-pump stages that meets the output requirement.  
SG  
normal operation, R  
carries a gate drive current of  
SG  
                         
���������������������������������������������������������������� ꢀMaxim Integrated Productsꢀ ꢀ 19  
MAX16929  
Automotive TFT-LCD Power Supply with Boost  
Converter and Gate Voltage Regulators  
The number of positive charge-pump stages needed is  
given by:  
switching frequency of the boost converter, and V  
RIPPLE_  
is the peak-to-peak value of the output ripple.  
CP  
V
+V  
V  
2 × V  
For the inverting charge pump connected to CN, use the  
following equation to approximate the required output  
capacitance:  
GH DROPOUT  
SH  
n
=
CP  
V
+V  
SH SCHOTTKY D  
and the number of negative charge-pump stages is  
given by:  
(1-D)×I  
LOAD_CN  
C
OUT_CN  
f
× V  
RIPPLE_CN  
SW  
|V |+V  
GL  
DROPOUT  
n
=
CN  
where C  
is the output capacitor of the charge  
pump, D is the duty cycle of the boost converter,  
OUT_CN  
V
+ V  
2 × V  
SH  
SCHOTTKY D  
where n  
is the number of positive charge-pump stag-  
is the number of negative charge-pump stages,  
I
is the load current of the charge pump, f  
CP  
LOAD_CN SW  
es, n  
is the switching frequency of the boost converter, and  
V
ripple.  
CN  
V
GH  
is the positive-gate voltage regulator output volt-  
is the peak-to-peak value of the output  
RIPPLE_CN  
age, V  
is the negative-gate voltage regulator output  
GL  
voltage, V  
is the boost converter’s output voltage, V  
SH  
D
Charge-Pump Rectifier Diodes  
is the forward-voltage drop of the charge-pump diode,  
is the forward drop of the Schottky diode  
Use high-speed silicon switching diodes with a current  
rating equal to or greater than two times the average  
charge-pump input current. If it helps avoid an extra  
stage, some or all of the diodes can be replaced with  
Schottky diodes with an equivalent current rating.  
V
SCHOTTKY  
of the boost converter, and V  
is the dropout  
= 0.3V for the  
= 2V at 20mA  
DROPOUT  
DROPOUT  
DROPOUT  
margin for the regulator. Use V  
negative voltage regulator and V  
for the positive-gate voltage regulator.  
Positive-Gate Voltage Regulator  
Flying Capacitors  
Increasing the flying capacitor (C ) value lowers the  
Output-Voltage Selection  
The output voltage of the positive-gate voltage regula-  
tor can be adjusted by using a resistive voltage-divider  
X
effective source impedance and increases the output  
current capability. Increasing the capacitance indefi-  
nitely has a negligible effect on output current capability  
because the internal switch resistance and the diode  
impedance place a lower limit on the source impedance.  
A 0.1FF ceramic capacitor works well in most low-current  
applications. The voltage rating of the flying capacitors  
formed by R  
and R  
. Connect R  
between  
between  
TOP  
BOTTOM  
TOP  
the output and FBGH, and connect R  
FBGH and GND. Select R  
BOTTOM  
in the 10kI to 50kI  
BOTTOM  
range. Calculate R  
with the following equation:  
TOP  
V
GH  
R
= R  
× (  
BOTTOM  
1)  
for the positive charge pump should exceed V , and  
TOP  
CP  
V
FBGH  
that for the negative charge pump should exceed the  
magnitude of V  
.
CN  
where V  
is the desired output voltage and V  
= 1V  
FBGH  
GH  
(the regulated feedback voltage for the regulator). Place  
both resistors as close as possible to the device.  
Charge-Pump Output Capacitor  
Increasing the output capacitance or decreasing the ESR  
reduces the output-ripple voltage and the peak-to-peak  
transient voltage. With ceramic capacitors, the output-  
voltage ripple is dominated by the capacitance value.  
Use the following equation to approximate the required  
output capacitance for the noninverting charge pump  
connected to CP:  
Avoid excessive power dissipation within the internal  
pMOS device of the regulator by paying attention to the  
voltage drop across the drain and source. The amount of  
power dissipation is given by:  
P
GL  
= (V - V ) × I  
CP GH LOAD(MAX)  
where V  
age applied to the drain, V  
voltage, and I is the maximum load current.  
is the noninverting charge-pump output volt-  
CP  
D×I  
LOAD_CP  
is the regulated output  
GH  
C
OUT_CP  
f
× V  
RIPPLE_CP  
SW  
LOAD(MAX)  
Stability Requirements  
The positive-gate voltage regulator (GH) requires a  
minimum output capacitance for stability. For an output  
where C  
is the output capacitor of the charge  
OUT_CP  
pump, D is the duty cycle of the boost converter, I  
LOAD_  
is the  
SW  
is the load current of the charge pump, f  
CP  
                         
���������������������������������������������������������������� ꢀMaxim Integrated Productsꢀ ꢀ 20  
MAX16929  
Automotive TFT-LCD Power Supply with Boost  
Converter and Gate Voltage Regulators  
voltage of 5V to (V  
10mA to 15mA, use a minimum capacitance of 0.47FF.  
- 2V) and an output current of  
output voltage applied to the emitter of the transistor,  
and I is the maximum load current. Note  
that the external transistor is not short-circuit protected.  
CP  
LOAD(MAX)_GL  
Negative-Gate Voltage Regulator  
Stability Requirements  
The device’s negative-gate voltage regulator uses an  
internal transconductance amplifier to drive an external  
pass transistor. The transconductance amplifier, the  
pass transistor, the base-emitter resistor, and the output  
capacitor determine the loop stability.  
Output-Voltage Selection  
The output voltage of the negative-gate voltage regula-  
tor can be adjusted by using a resistive voltage-divider  
formed by R  
REF and FBGL, and connect R  
and R  
. Connect R  
between  
TOP  
BOTTOM  
TOP  
between FBGL  
BOTTOM  
and the collector of the external npn transistor. Select  
greater than 20kI to avoid loading down the ref-  
R
TOP  
The transconductance amplifier regulates the output volt-  
age by controlling the pass transistor’s base current. The  
total DC loop gain is approximately:  
erence output. Calculate R  
equation:  
with the following  
BOTTOM  
V
V  
GL  
FBGL  
R
= R  
×
TOP  
I
×h  
I
LOAD  
BOTTOM  
4
BIAS  
FE  
V
V  
A
( )× (1+  
)× V  
REF  
REF  
FBGL  
V_GL  
V
T
where V  
is the desired output voltage, V  
= 0.25V (the regulated feedback voltage of  
= 1.25V,  
GL  
REF  
where V is 26mV at room temperature, and I  
current through the base-to-emitter resistor (R ). For  
is the  
BIAS  
BE  
T
and V  
FBGL  
the regulator).  
the device, the bias current for the negative-gate voltage  
regulator is 0.1mA. Therefore, the base-to-emitter resistor  
should be chosen to set 0.1mA bias current:  
Pass Transistor Selection  
The pass transistor must meet specifications for current  
gain (h ), input capacitance, collector-emitter saturation  
FE  
V
0.7V  
BE  
voltage, and power dissipation. The transistor’s current  
gain limits the guaranteed maximum output current to:  
R
=
=
= 7kΩ  
BE  
0.1mA 0.1mA  
Use the closest standard resistor value of 6.8kI. The  
output capacitor and the load resistance create the  
dominant pole in the system. However, the internal  
amplifier delay, pass transistor’s input capacitance,  
and the stray capacitance at the feedback node create  
additional poles in the system, and the output capacitor’s  
ESR generates a zero. For proper operation, use the fol-  
lowing equations to verify that the regulator is properly  
compensated:  
V
BE  
I
= (I  
)×h  
FE(MIN)  
LOAD(MAX)  
DRVN  
R
BE  
where I  
rent, V  
is the minimum guaranteed base-drive cur-  
is the transistor’s base-to-emitter forward volt-  
DRVN  
BE  
age drop, and R  
is the pulldown resistor connected  
BE  
between the transistor’s base and emitter. Furthermore,  
the transistor’s current gain increases the regulator’s DC  
loop gain (see the Stability Requirements section), so  
excessive gain destabilizes the output.  
1) First, determine the dominant pole set by the regula-  
tor’s output capacitor and the load resistor:  
The transistor’s saturation voltage at the maximum output  
current determines the minimum input-to-output volt-  
age differential that the regulator can support. Also, the  
package’s power dissipation limits the usable maximum  
input-to-output voltage differential. The maximum power-  
dissipation capability of the transistor’s package and  
mounting must exceed the actual power dissipated in  
the device. The power dissipated equals the maximum  
I
LOAD(MAX)_GL  
f
=
POLE_GL  
2π × C  
× V  
OUT_GL  
OUT_GL  
The unity-gain crossover frequency of the regulator is:  
= A × f  
f
CROSSOVER  
V_GL  
POLE_GL  
2) The pole created by the internal amplifier delay is  
approximately 1MHz:  
load current (I  
) multiplied by the maximum  
LOAD(MAX)_GL  
input-to-output voltage differential:  
= (V - V ) × I  
LOAD(MAX)_GL  
f
= 1MHz  
POLE_AMP  
P
NPN_GL  
GL  
CN  
3) Next, calculate the pole set by the transistor’s input  
capacitance, the transistor’s input resistance, and the  
base-to-emitter pullup resistor:  
where V  
tor of the transistor, V  
is the regulated output voltage on the collec-  
GL  
is the inverting charge-pump  
CN  
                         
���������������������������������������������������������������� ꢀMaxim Integrated Productsꢀ ꢀ 21  
MAX16929  
Automotive TFT-LCD Power Supply with Boost  
Converter and Gate Voltage Regulators  
Tableꢀ4.ꢀMinimumꢀOutputꢀCapacitanceꢀvs.ꢀ  
OutputꢀVoltageꢀRangeꢀforꢀNegative-Gateꢀ  
1
f
=
POLE_IN  
2π × C × (R /R  
)
IN  
BE IN  
VoltageꢀRegulatorꢀ(I ꢀ=ꢀ10mAꢀtoꢀ15mA)  
OUT  
where:  
g
h
FE  
OUTPUTꢀVOLTAGEꢀ  
RANGE  
MINIMUMꢀOUTPUTꢀ  
CAPACITANCEꢀ(µF)  
m
C
=
, R  
=
IN  
IN  
2πf  
g
T
m
-2V R V Rꢀ-4V  
2.2  
1.5  
1
GL  
g
is the transconductance of the pass transistor, and  
m
-5V R V R -7V  
GL  
f is the transition frequency. Both parameters can be  
T
-8V R V R -13V  
found in the transistor’s data sheet. Because R  
is  
GL  
BE  
much greater than R , the above equation can be  
simplified:  
IN  
Applications Information  
1
2π × C ×R  
f
=
POLE_IN  
Power Dissipation  
An IC’s maximum power dissipation depends on the ther-  
mal resistance from the die to the ambient environment  
and the ambient temperature. The thermal resistance  
depends on the IC package, PCB copper area, other  
thermal mass, and airflow. More PCB copper, cooler  
ambient air, and more airflow increase the possible dis-  
sipation, while less copper or warmer air decreases the  
IC’s dissipation capability. The major components of  
power dissipation are the power dissipated in the buck  
converter, boost converter, positive-gate voltage regula-  
tor, negative-gate voltage regulator, and the 1.8V/3.3V  
regulator controller.  
IN  
IN  
Substituting for C and R yields:  
IN  
IN  
f
T
f
=
POLE  
h
FE  
4) Next, calculate the pole set by the regulator’s feed-  
back resistance and the capacitance between FBGL  
and GND (including stray capacitance):  
1
× (R  
f
=
POLE_FBGL  
2π × C  
/R  
)
FBGL  
TOP BOTTOM  
where C  
GND and is equal to 30pF, R  
of the regulator’s feedback divider, and R  
the lower resistor of the divider.  
is the capacitance between FBGL and  
FBGL  
is the upper resistor  
TOP  
Buck Converter  
In the buck converter, conduction and switching losses  
in the internal MOSFET are dominant. Estimate these  
losses using the following formula:  
is  
BOTTOM  
5) Next, calculate the zero caused by the output capaci-  
tor’s ESR:  
2
P
[(I  
× D) × R  
OUTB  
] + [0.5 × V  
×
LXB  
OUTB  
DS_ON(LXB)  
INB  
1
I
× (t + t ) × f  
]
f
=
R
F
SWB  
ZERO_ESR  
2π × C  
×R  
ESR  
OUT_LR  
where I  
is the output current, D is the duty cycle  
OUTB  
of the buck converter, R  
is the on-resistance  
is the input voltage,  
(t + t is the time is takes for the switch current and  
where R  
C
is the equivalent series resistance of  
DS_ON(LXB)  
ESR  
of the internal high-side FET, V  
. To ensure stability, make C  
large  
INB  
OUT_LR  
OUT_LR  
enough so the crossover occurs well before the poles  
and zero calculated in steps 2 to 5. The poles in steps  
3 and 4 generally occur at several MHz and using  
ceramic capacitors ensures the ESR zero also occurs  
at several MHz. Placing the crossover frequency below  
500kHz is sufficient to avoid the amplifier delay pole  
and generally works well, unless unusual component  
choices or extra capacitances move one of the other  
poles or the zero below 1MHz.  
R
F)  
voltage to settle to their final values during the rising and  
falling transitions, and f  
of the buck converter. R  
is the switching frequency  
is 180mI (typ) and  
(t + t is 4.4ns + 4.6ns = 9ns at V = 12V.  
SWB  
DS_ON(LXB)  
R
F)  
INB  
Table 4 is a list of recommended minimum output capaci-  
tance for the negative-gate voltage regulator and are  
applicable for output currents in the 10mA to 15mA range.  
                         
���������������������������������������������������������������� ꢀMaxim Integrated Productsꢀ ꢀ 22  
MAX16929  
Automotive TFT-LCD Power Supply with Boost  
Converter and Gate Voltage Regulators  
Boost Converter  
Power dissipation in the boost converter is primarily due  
to conduction and switching losses in the low-side FET.  
Conduction loss is produced by the inductor current  
flowing through the on-resistance of the FET during the  
on-time. Switching loss occurs during switching transi-  
tions and is a result of the finite time needed to fully turn  
on and off the FET. Power dissipation in the boost con-  
verter can be estimated with the following formula:  
Positive-Gate Voltage Regulator  
Use the lowest number of charge-pump stages possible  
in supplying power to the positive-gate voltage regulator.  
Doing so minimizes the drain-source voltage of the inte-  
grated pMOS switch and power dissipation. The power  
dissipated in the switch is given as:  
P
GH  
= (V - V ) × I  
CP GH LOAD(MAX)_GH  
Ensure that the voltage on CP does not exceed the  
CP overvoltage threshold as given in the Electrical  
Characteristics table.  
2
P
[(I  
IN(DC,MAX)  
× D) × R  
] + V  
×
LXP  
IN(DC,MAX)  
DS_ON(LXP)  
SH  
I
× f  
× [(t  
+ t ) + (t + t )]  
SW  
R-V F-I R-I F-V  
Negative-Gate Voltage Regulator  
Use the lowest number of charge-pump stages possible  
to provide the negative voltage to the negative-gate  
voltage regulator. Estimate the power dissipated in the  
negative-gate voltage regulator using the following:  
where I  
is the maximum expected average  
IN(DC,MAX)  
input (i.e., inductor) current, D is the duty cycle of the  
boost converter, R  
the internal low-side FET, V  
is the on-resistance of  
is the output voltage, and  
DS_ON(LXP)  
SH  
f
R
is the switching frequency of the boost converter.  
SW  
P
GL  
= (V + |V | - V ) × I  
INA CN BE DRVN  
is 110mI (typ) and f  
is 2.2MHz.  
DS_ON(LXP)  
SW  
where V is the base-emitter voltage of the external npn  
BE  
The voltage and current rise and fall times at the LXP  
node are equal to t (voltage rise time), t (voltage fall  
bipolar transistor, and I  
is the current sourced from  
DRVN  
R-V  
F-V  
DRVN to the R  
bias resistor and to the base of the  
BE  
time), t  
(current rise time), and t (current fall time),  
R-I  
F-I  
transistor, which is given by:  
and are determined as follows:  
V
I
GL  
BE  
I
=
+
DRVN  
V
+ V  
SCHOTTKY  
SH  
R
h
+1  
t
t
=
=
BE  
FE  
R-V  
F-V  
K
R-V  
1.8V/3.3V Regulator Controller  
The power dissipated in the 1.8V/3.3V regulator controller  
is given by:  
V
+ V  
K
SH  
SCHOTTKY  
F-V  
P
= (V  
- V  
- V ) × I  
REG  
INA  
OUT_REG BE DR  
I
IN(DC,MAX)  
where V  
= 1.8V or 3.3V, V is the base-emitter  
BE  
t
=
=
OUT_REG  
R-I  
F-I  
K
voltage of the external npn bipolar transistor, and I  
is  
R-I  
DR  
the current sourced from DR to the base of the transistor.  
is given by:  
I
IN(DC,MAX)  
I
DR  
t
K
I
F-I  
LOAD  
I
=
DR  
h
+1  
FE  
K
R-V  
, K , K , and K  
are the voltage and current  
F-I  
slew rates of the LXP node and are supply dependent.  
Use Table 5 to determine their values.  
F-V  
R-I  
where I  
is load current of the 1.8V/3.3V regulator  
FE  
LOAD  
controller, and h is the current gain of the transistor.  
Tableꢀ5.ꢀLXPꢀVoltageꢀandꢀCurrentꢀSlewꢀRatesꢀvs.ꢀSupplyꢀVoltage  
LXPꢀVOLTAGEꢀANDꢀCURRENTꢀSLEWꢀRATES  
RISINGꢀVOLTAGE  
SLEWꢀRATE  
FALLINGꢀVOLTAGE  
SLEWꢀRATE  
RISINGꢀCURRENT  
SLEWꢀRATE  
FALLINGꢀCURRENT  
SLEWꢀRATE  
V
ꢀ(V)  
INA  
K
ꢀ(V/ns)  
K
ꢀ(V/ns)  
K
ꢀ(A/ns)  
K
ꢀ(A/ns)  
R-V  
F-V  
R-I  
F-I  
3.3  
0.52  
1.35  
1.7  
2
0.13  
0.3  
0.38  
0.44  
5
                         
���������������������������������������������������������������� ꢀMaxim Integrated Productsꢀ ꢀ 23  
MAX16929  
Automotive TFT-LCD Power Supply with Boost  
Converter and Gate Voltage Regulators  
Total Power Dissipation  
The total power dissipated in the package is the sum of  
the losses previously calculated. Therefore, total power  
dissipation can be estimated as follows:  
2) Connect input and output capacitors to the power  
ground planes; connect all other capacitors to the  
analog ground plane.  
3) Keep the high-current paths as short and wide as  
possible. Keep the path of switching currents short.  
P = P  
+ P  
+ P + P + P  
GH GL REG  
T
LXB  
LXP  
Achieve maximum heat transfer by connecting the exposed  
pad to a thermal landing pad and connecting the thermal  
landing pad to a large ground plane through thermal vias.  
4) Place the feedback resistors as close to the IC as  
possible. Connect the negative end of the resistive  
divider and the compensation network to the analog  
ground plane.  
Layout Considerations  
Careful PCB layout is critical in achieving stable and  
optimized performance. Follow the following guidelines  
for good PCB layout:  
5) Route the high-speed switching node LXB and LXP  
away from sensitive analog nodes (FB, FBP, FBGH,  
FBGL, FBB, and REF).  
Refer to the MAX16929 Evaluation Kit data sheet for a  
recommended PCB layout.  
1) Place decoupling capacitors as close as possible to  
the device. Connect the power ground planes and the  
analog ground plane together at one point close to the  
device.  
Ordering Information/Selector Guide  
REGULATOR  
ꢀ(V)  
BUCK  
BUCK  
BOOST  
(A)  
PART  
PIN-PACKAGE  
V
V
(V)  
I
ꢀ(A)  
OUTB  
2
I
LIM  
REG  
OUTBꢀ  
MAX16929AGUI/V+  
MAX16929BGUI/V+  
MAX16929CGUI/V+  
MAX16929DGUI/V+  
MAX16929EGUI/V+  
MAX16929FGUI/V+  
MAX16929GGUI/V+  
MAX16929HGUI/V+  
MAX16929IGUI/V+  
3.3  
1.8  
1.8  
3.3  
3.3  
1.8  
1.8  
1.8  
1.8  
5
5
1.5  
28 TSSOP-EP*  
28 TSSOP-EP*  
28 TSSOP-EP*  
28 TSSOP-EP*  
28 TSSOP-EP*  
28 TSSOP-EP*  
28 TSSOP-EP*  
28 TSSOP-EP*  
28 TSSOP-EP*  
2
1.5  
3.3  
5
2
1.5  
2
0.75  
0.75  
0.75  
0.75  
0.75  
0.75  
5
1.2  
2
5
5
1.2  
2
3.3  
3.3  
1.2  
Note: All devices are specified over the -40°C to +105°C operating temperature range.  
/V denotes an automotive qualified part.  
+Denotes a lead(Pb)-free/RoHS-compliant package.  
*EP = Exposed pad.  
Chip Information  
Package Information  
For the latest package outline information and land patterns  
(footprints), go to www.maxim-ic.com/packages. Note that a  
“+”, “#”, or “-” in the package code indicates RoHS status only.  
Package drawings may show a different suffix character, but  
the drawing pertains to the package regardless of RoHS status.  
PROCESS: BiCMOS  
PACKAGEꢀ  
TYPE  
PACKAGEꢀ  
CODE  
OUTLINEꢀ  
NO.  
LANDꢀ  
PATTERNꢀNO.  
28 TSSOP-EP  
U28ME+1  
21-0108  
90-0147  
                         
���������������������������������������������������������������� ꢀMaxim Integrated Productsꢀ ꢀ 24  
MAX16929  
Automotive TFT-LCD Power Supply with Boost  
Converter and Gate Voltage Regulators  
Typical Application Circuit  
OUTB  
R
COMPV  
C
COMPI  
C
COMPV  
COMPI  
COMPV  
GATE  
INA  
L
P
OPTIONAL  
LXP  
V
SH  
DR  
FB  
V TO 18V  
INA  
BOOST  
1.8V/3.3V  
REGULATOR  
CONTROLLER  
PGNDP  
FBP  
V
REG  
1.8V/3.3V  
LXP  
V
OSCILLATOR  
CN  
V
CN  
CP  
DRVN  
FBGL  
V
SH  
POSITIVE  
GATE  
VOLTAGE  
REGULATOR  
NEGATIVE  
GATE  
VOLTAGE  
REGULATOR  
GH  
V
GH  
V
GL  
FBGH  
BST  
INB  
4V TO 28V  
REF  
BANDGAP  
REFERENCE  
3.3V/5V  
BUCK  
GND  
LXB  
OUTB  
ENP  
SEQ  
INA  
CONTROL  
FBB  
ENB  
AVL  
GND  
PGOOD  
MAX16929  
MAX16929  
Automotive TFT-LCD Power Supply with Boost  
Converter and Gate Voltage Regulators  
Revision History  
REVISION REVISION  
PAGES  
CHANGED  
DESCRIPTION  
NUMBER  
DATE  
5/11  
9/11  
1/12  
0
1
2
Initial release  
Removed ENB from the FBB to GND range in the Absolute Maximum Ratings  
Corrected the C formula in the Loop Compensation section  
2
18  
COMPI  
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. The parametric values (min and max limits) shown in the Electrical  
Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.  
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600  
25  
©
2012 Maxim Integrated Products  
Maxim is a registered trademark of Maxim Integrated Products, Inc.  

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