ZLED7002ZI1R ZMDI, ZLED7002ZI1R Datasheet - Page 8

• Manufacturer Part Number: ZLED7002ZI1R
• Description: LED Lighting Drivers LED driver
• Manufacturer: ZMDI

Specifications of ZLED7002ZI1R

• Rohs: yes
• Input Voltage: 2.7 V to 5.5 V
• Maximum Supply Current: 320 uA
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Package / Case: SOP-8
• Minimum Operating Temperature: - 25 C

2.2.
The ZLED7002’s UV pin enables under-voltage detection. When a high-to-low transition occurs on the power supply voltage
and the voltage at the UV pin falls below the under-voltage threshold (typically 1.17V), the ZLED7002 automatically turns off
the MAIN LED channel and actives the SUB channel. There is an 80mV hysteresis for the under-voltage threshold to prevent
unintended activation due to power supply ripple. When a low-to-high transition occurs on the power supply voltage, the SUB
channel is turned off and the MAIN channel is activated if the UV pin voltage is 80mV (typical) above the under-voltage
threshold.
The voltage at the UV pin (V
connect to the UV pin to form a voltage divider across the power supply. V
If the values for R1 and R2 are low, high current will flow through them resulting in lower system efficiency. Typical values for
R1 and R2 are in the magnitude of 10
compute R1 as needed to achieve the target ratio.
For applications using a lithium battery, which typically maintains ~3.7V during its discharge stage, setting V
recommended.
2.3.
The R3 resistor connected between the Iset and GND pins determines the level of the constant current through the MAIN LED
channel, which is typically 8000 times the current of the Iset pin. The voltage at the Iset pin is a constant 1.2V, which is
unaffected by environmental temperature and any power supply voltage changes as shown in Figure 1.1 and Figure 1.2.
The MAIN LED current flows through the MAIN pin to ground, so voltage dropout is minimal (as low as 0.1V when the MAIN
channel current is 200mA).
Note: System efficiency is reduced if the power supply voltage is larger than the MAIN LED’s voltage. In this case, the
additional voltage is added to the MAIN pin voltage.
The MAIN LED channel current (I
2.4.
The SUB LED channel current is determined by the external R4 resistor in series with the connected SUB LED string, the SUB
LED forward voltage, and the voltage drop across the D1 Zener diode connected from the cathode of the SUB LED to the SUB
pin. When the SUB channel is active, its current flows through the SUB pin to ground.
Data Sheet
August 10, 2011
ZLED7002
Toggle (Side-Step) Dual-Channel LED Driver
Under-Voltage Threshold
Main LED Current
Sub LED Current
V
I
UV
MAIN
PIN
8000
V
© 2011 Zentrum Mikroelektronik Dresden AG — Rev.3.0
All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without
the prior written consent of the copyright owner. The information furnished in this publication is subject to changes without notice.
CC






V
R
ISET
R
1
3
R
UV-PIN
2



R
MAIN
2



) is determined by the ratio of the external resistors R1 and R2 (see Figure 3.1), which
) is calculated via equation (2):
5
; e.g., 51k . For design purposes, it is helpful to select the value for R2 first and then
UV-PIN
can be calculated with equation (1):
(1)
(2)
UV-PIN
8 of 13
to 3.4V is