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PDF AT9917 Data sheet ( Hoja de datos )
| Número de pieza | AT9917 | |
| Descripción | Automotive LED Driver IC | |
| Fabricantes | Supertex | |
| Logotipo |  |
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Supertex inc.
AT9917www.DataSheet4U.com
Automotive LED Driver IC
with High Current Accuracy
Features
► Switch mode controller for boost, SEPIC & buck
converters
► Closed loop control of output current
► High PWM dimming ratio
► Internal 40V linear regulator
► Internal 3% voltage reference
► Constant frequency operation with programmable
slope compensation
► Linear and PWM dimming
► Programmable jitter to reduce EMI
► +/-1.0A MOSFET gate driver
► Output short circuit protection
► Output over voltage protection
► Programmable hiccup timer
► Temperature fold-back with external NTC resistor
► Soft start
► Meets AEC-Q100 requirements
Applications
► Automotive LED driver applications
General Description
The AT9917 is an advanced fixed frequency PWM IC
designed to control single-switch, boost, SEPIC, and buck
LED drivers in a constant current mode. The controller uses a
peak current-mode control scheme (with programmable slope
compensation) and includes an internal transconductance
amplifier to control the output current with high accuracy.
The IC includes a +/-1A gate driver that makes the AT9917
suitable for high power applications. An internal 40V linear
regulator powers the IC eliminating the need for a separate
power supply for the IC. The IC provides a FAULT output,
which can be used to disconnect the LEDs in case of a fault
condition (such as an alternator load dump in automobiles)
using an external disconnect FET. AT9917 also provides a
TTL compatible, low-frequency PWM dimming input that
can accept an external control signal with a duty ratio of 0-
100% and a frequency of up to several kilohertz. Temperature
foldback of the output current is possible, using an external
NTC resistor.
The AT9917-based LED driver is suited for automotive LED
driver applications. The AT9917 based LED lamp drivers can
achieve efficiencies in excess of 90% when buck or boost
topologies are used.
Typical Boost Application Circuit
CIN
CIN1
L1
D2 (Optional)
D1
Q1
Co
CPVDD
CSC
RSC
RCS
PVDD AVDD GT
VIN
CS
GND
EN
PWMD
AT9917
PGND OVP
FLT
FDBK
COMP
R4
CC
RT IREF
RT SS JT NTC DIV T1 T2 REF
CSS
CJTR
R1 RR1
R3 CREF
R2
RR2
Q2
RS
Supertex inc. ● 1235 Bordeaux Drive, Sunnyvale, CA 94089 ● Tel: 408-222-8888 ● www.supertex.com
1 page  
AT9917
www.DataSheet4U.com
Functional Block Diagram
VIN
AVDD
EN
RT
CS
COMP
SS
FDBK
IREF
Linear
Regulator
4.25V/4.50V
+
0.8V/2V _
HCP
_+
Vbg
POR
POR
FC
GATE
Clock
SQ
JTR HCP
Blanking
GATE
14R
+
_
R
DIS
POR
_GM
OVPD
SCD
OTP
POR
HCP
0.7V
+
-
R
IDRP
=
4
30
(INTC
-
3ITI)
Current Mirror
+
-
INTC
IT1 IT2
FC
1.25V/1.125V
OVPD
S Q DIS
R Q FC
2 250mV
OTP JTR
Jitter
TBLANK
+
_
HCP
DIS
SCD
REF
PVDD
GATE
PGND
FLT
OVP
GND
PWMD
NTC
DIV T1 T2
JTR
Supertex inc. ● 1235 Bordeaux Drive, Sunnyvale, CA 94089 ● Tel: 408-222-8888 ● www.supertex.com
5
5 Page 
AT9917
www.DataSheet4U.com
Pin Description
Pin # Name Description
1 VIN This pin is the input of a 40V high voltage regulator.
2
AVDD
This is a power supply pin for all internal circuits. It must be bypassed with a low ESR capacitor to
GND (at least 0.1μF).
3
PVDD
This is the power supply pin for the gate driver. It should be connected externally to AVDD and by-
passed with a low ESR capacitor to PGND (at least 0.1μF).
4 GATE This pin is the output gate driver for an external logic level N-channel power MOSFET.
5 PGND Ground return for the gate drive circuitry.
6
GND
Ground return for all the low power analog internal circuitry. This pin must be connected to the return
path from the input.
7
JTR
This pin controls the jitter of the clock programmed by a capacitor connected at this pin. This capacitor
also determines the hiccup time.
8
RT
This pin sets the frequency of the power circuit. A resistor between RT and GND will program the
circuit in constant frequency mode.
This pin is used to sense the source current of the external power FET. It includes a built-in 100ns
9 CS (min) blanking time. Slope compensation is implemented by connecting an RC network to this pin as
shown in the Typical Application.
This pin provides the over voltage protection for the converter. When the voltage at this pin exceeds
10 OVP 1.25V, the gate output of the AT9917 is turned off and FLT goes low. Switching is enabled when the
voltage at this pin goes below 1.125V.
11
T2
This current programs the temperature at which the driver is shut off due to over temperature condi-
tions for the LED.
12
T1
This current input programs the break temperature threshold which determines the start of the current
derating when using the external NTC resistor.
13 RNTC Connect an external NTC resistor to this pin for temperature fold-back of the output current.
14 DIV Programs the voltage input for the transconductance at NTC pin.
This pin is pulled to ground when there is an output short circuit condition or output over voltage condi-
15
FLT
tion. This pin can be used to drive an external MOSFET in the case of boost converters to disconnect
the load from the source. It is also controlled by the PWM dimming input to provide excellent PWM
dimming response.
16
PWMD
When this pin is pulled to GND (or left open), switching of the AT9917 is disabled. When an external
TTL high level is applied to it, switching will resume.
17 SS Connecting a capacitor from this pin to GND programs the soft start time of the LED driver.
18
COMP
Stable closed loop control can be accomplished by connecting a compensation network between
COMP and GND. This pin is discharged upon detection of a fault condition and on startup.
19
IREF
The voltage at this pin sets the output current level. The current reference can be set using a resistor
divider from the REF pin.
20
FDBK
This pin provides output current feedback to the AT9917 by using a current sense resistor. A resistor
in series with the FDBK pin can be used to reduce the current at elevated temperatures.
21 NC
No connection.
22 NC
23
EN
Pulling EN to GND causes the AT9917 to go into a low current standby mode. A voltage greater than
2.0V will cause the IC to start up.
24
REF
This pin provides accurate reference voltage. It must be bypassed with a 0.01μF -0.1μF capacitor to
GND.
Supertex inc. ● 1235 Bordeaux Drive, Sunnyvale, CA 94089 ● Tel: 408-222-8888 ● www.supertex.com
11
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet AT9917.PDF ] | |
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