ON Semiconductor NCL30105G1EVB VCSEL Driver with Buck PWM Controller Evaluation Board User Manual
- June 5, 2024
- ON Semiconductor
Table of Contents
www.onsemi.com
EVAL BOARD USER’S MANUAL
VCSEL Driver with Buck PWM Controller Evaluation Board
User’s Manual
NCL30105G1EVB
Overview
This manual covers the specification, theory of operation, testing, and construction of the NCL30105G1EVB evaluation board. This evaluation board uses NCL30105 as a high pulse current low duty cycle VCSEL driver. The expected duty cycle is less than 5% in typical applications. The NCL30105 is an inverted buck converter design with constant off-time control.
Features
The key features of this evaluation board include:
- High Peak Current
- Small Size
- Fast Rise/Fall Time
- PWM Control
SPECIFICATIONS
Input voltage | 8.8 V dc – 22 V (lc | Nom. |
---|---|---|
Output Voltage | 3 V (lc | Nom. |
Output Current | 4 A | Peak |
Output Ripple | ± 6.5% | |
Output Rise/Fall Time | Bps/ 36 us | |
Switching Frequency | 146 kHz | @12 V |
Dimming Interface | PWM | SMA connector |
PCB Size | 25mmx 55mm |
THEORY OF OPERATION
Overview
The NCL30105G1EVB drives a low voltage high current VCSEL for camera
illumination for the automotive market.
Current Control
The NCL30105 is a peak current mode control with constant off time. Peak
current control provides accurate current regulation. The value of R7 sets the
peak current as follows:
The soft-start pin controls the peak current at turn-on. A capacitor on this pin is charged up by a 20 or internal current source. For PWM operation this capacitor is very small to allow for fast rise times. Analog dimming can be done by programming the voltage on the soft-start pin. The connection for this option is not brought out on this demo board although this control method is still available. The off-time is held constant in operation. R5 programs the off time. Constant off-time control eliminates sub-harmonic oscillation in buck converters where the duty cycle exceeds 50%. The on-time is determined by the input voltage, the output voltage, and the inductor value.
Consequently, the switching frequency will vary over the line and load
conditions even though the off time is constant. The NCL30105 has a maximum
on-time ~34us which is set internally.
Vcc
Q1 is an emitter follower that limits Vcc to ~14 V. The NCL30105 has an upper
Vcc limit of 22 V. Some automotive applications exceed the 22 V limit,
especially in the case of
load dump.
Current Sense
The current sense pin has a Leading Edge Blanking (LEB) function to avoid
false triggering of the current sense comparator. The LEB is ~500 ns.
Dimming
The demo board is set up for PWM dimming through J3 (SMA). A 0−5 V square wave
signal will provide PWM dimming. In the absence of a signal to J3, the output
defaults
to off.
The output current (green trace) follows the PWM input signal (yellow trace).
The output filter affects the rise and fall times.
The rise and fall times are affected by the
output filter values. Raising the FSW will reduce the size requirement for the
output capacitor which reduces rise and fall times.
Reducing the off time will increase the switching frequency and reduce the
current ripple for a given output inductor.
SCHEMATIC
BILL OF MATERIAL
Qty
| Reference| Part| Distributor| Dist. PIN| Manufacturer| Mfr_PN| Insert|
Safety
Controlled
---|---|---|---|---|---|---|---|---
5| C1, C2,
C3, C4,
C6| 4.7 pF 25 V| Digikey| 1276-3178-1-ND| Samsung| CL31B475KAHN
NEW| Yes| No
2| C5, C7| 220 pF| Digikey| 311-1416-1-ND| Yageo| CC0402JRNP09
BN221| Yes| No
1| D1| FSV530AF| ON
Semiconductor| FSV530AFCT-ND| ON
Semiconductor| FSV530AF| Yes| No
1| D2| SZMM3Z15V
T1G| ON
Semiconductor| SZMM3Z15VT1GOS
CT-ND| ON
Semiconductor| SZMM3Z15VT1G| Yes| No
1| J1| CONN JACK
PWR| Digikey| 732-5929-1-ND| Wurth| 694106106102| Yes| No
1| J2| OSTTA024163| Digikey| ED2580-ND| On Shore| OSTTA024163| Yes| No
1| J3| SMA| Digikey| WM5525-ND| Molex| 731000114| Yes| No
1| L1| 4.7 RH| Digikey| 587-1624-1-ND| Taiyo Yuden| CBC3225T4R7MR| Yes| No
1| L2| 15 pH| Digikey| 732-1242-1-ND| Wurth| 7447709150| Yes| No
1| Q1| MMBT3904W
T1G| ON
Semiconductor| MMBT3904WT1G| ON
Semiconductor| MMBT3904VVT1G| Yes| No
1| Q2| NVMFS5C46
8NT1G| ON
Semiconductor| NVMFS5C468NT1G
OSCT-ND| ON
Semiconductor| NVMFS5C468NT
1G| Yes| No
1| R1| 10k| Digikey| 311-10.0KLRCT-ND| Yago| RC0402FR-0710
KL| Yes| No
2| R2, R3| 49.9| Digikey| 311-49.9LRCT-ND| Yago| RC0402FR-0749
R9L| Yes| No
2| R4, R6| 100| Digikey| 311-100LRCT-ND| Yago| RC0402FR-0710
ORL| Yes| No
1| R5| 30k| Digikey| 311-30.0KLRCT-ND| Yago| RC0402FR-0730
KL| Yes| No
1| R7| 220m| Digikey| 408-1608-1-ND| Susumu| KRL2012E-M-R2
20-F-T5| Yes| No
1| U1| NCL30105DR
2G| ON
Semiconductor| NCL30105DR2GOS
CT-ND| ON
Semiconductor| NCL30105DR2G| Yes| No
TEST PROCEDURE
-
Require Equipment
a. DC Power Supply 12 V @ 2 A
b. Function Generator
c. LED Load similar to Luminus
CBT−90−B−L11−J101 (observe the correct polarity) -
Connector the LED Load to J2
-
Apply 12 V to J1 (2.1 x 5.5 Power Connector)
-
Connect a function generator and set it as follows:
a. Frequency – 100 Hz
b. Duty Cycle – 5%
c. Vin – 0−5 V (into a 50 Ω load) -
Observe that the output current transitions from 0 to ~4 A in sync with the function generator output.
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