Datasheet

LT3745
5
3745f
TiMing characTerisTics
The l denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C. V
IN
= 12V, V
CC
= 3V to 5.5V, V
EN/UVLO
= 1.5V, V
FB
= 1.5V,
V
ISP
= V
ISN
= 5V, V
LEDxx
= 1V, R
T
= 105k, R
ISET
= 60.4k, C
CAP
= 0.47µF to V
IN
, C
SCKO
= C
SDO
= C
LDO
= 15pF to GND, unless
otherwise noted.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
f
SCKI
Data Shift Clock Frequency
l
30 MHz
f
PWMCK
PWMCK Clock Frequency
l
25 MHz
t
WH-CKI
t
WL-CKI
SCKI Pulse Duration SCKI = H (Figure 3)
SCKI = L (Figure 3)
l
l
16
16
ns
ns
t
WH-PWM
t
WL-PWM
PWMCK Pulse Duration PWMCK = H (Figure 4)
PWMCK = L (Figure 4)
l
l
20
20
ns
ns
t
WH-LDI
LDI Pulse Duration LDI = H (Figure 3)
l
20 ns
t
SU-SDI
SDI-SCKI Setup Time
SDI – SCKI ↑ (Figure 3)
l
2 ns
t
HD-SDI
SCKI-SDI Hold Time
SCKI ↑ – SDI (Figure 3)
l
2 ns
t
SU-LDI
SCKI-LDI Setup Time
SCKI ↓ – LDI ↑ (Figure 3)
l
5 ns
t
HD-LDI
LDI-SCKI Hold Time
LDI ↓ – SCKI ↑ (Figure 3)
l
15 ns
t
PD-SCK↑
SCKI-SCKO Propagation Delay (Rising)
SCKI ↑ – SCKO ↑ (Figure 3)
l
17 35 ns
t
PD-SCK↓
SCKI-SCKO Propagation Delay (Falling)
SCKI ↓ – SCKO ↓ (Figure 3)
l
20 40 ns
∆t
PD-SCK
SCK Duty Cycle Change
∆t
PD-SCK
= t
PD-SCK↑
– t
PD-SCK↓
–3 ns
t
PD-SD
SCKO-SDO Propagation Delay
SCKO ↑ – SDO (Figure 3)
l
2.2 4.5 7 ns
t
PD-LD↑
LDI-LDO Propagation Delay (Rising)
LDI ↑ – LDO ↑ (Figure 3)
l
17 35 ns
t
PD-LD↓
LDI-LDO Propagation Delay (Falling)
LDI ↓ – LDO ↓ (Figure 3)
l
20 40 ns
∆t
PD-LD
LD Duty Cycle Change
∆t
PD-LD
= t
PD-LD↑
– t
PD-LD↓
–3 ns
t
PD-PWM
PWMCK-LED Propagation Delay
PWMCK ↑ – I
LED
(Figure 4)
80 ns
t
R-SO
SCKO/SDO/LDO Rise Time C
LOAD
= 15pF, 10% to 90% 4 ns
t
F-SO
SCKO/SDO/LDO Fall Time C
LOAD
= 15pF, 90% to 10% 4 ns
Table 1. Test Parameter Equations
∆I
LEDC
(%) =
I
OUTn
– I
OUTavg(0−15)
I
OUTavg(0−15)
• 100
(1)
∆I
LEDD
(%) =
I
OUTavg(0−15)
– I
OUTcal
I
OUTcal
• 100
(2)
I
OUTcal
= 2500 •
1.205V
R
ISET






(3)
∆I
LINE
(% / V) =
I
OUTn
V
CC
= 5.5V – I
OUTn
V
CC
= 3V
I
OUTn
V
CC
= 3V
•
100
2.5V
(4)
∆I
LOAD
(% / V) =
I
OUTn
V
OUTn
= 3V – I
OUTn
V
OUTn
= 1V
I
OUTn
V
OUTn
= 1V
•
100
2V
(5)